CA2528314C

CA2528314C - Breathable gas apparatus with humidifier

Info

Publication number: CA2528314C
Application number: CA2528314A
Authority: CA
Inventors: Barton John Kenyon; Arthur Kin-Wai Yee; Rohan Neil Primrose; Jim Saada; John Michael Snow; Marek Tomasz Sapula; Geoffrey Crumblin; Duncan Lovel Trevor-Wilson; Perry David Lithgow; Alexander Virr; Donald Angus Richmond; Simone Marie Jeha; Mark John Payne; Andrew Charles Murray
Original assignee: Resmed Pty Ltd
Current assignee: Resmed Pty Ltd
Priority date: 2003-06-20
Filing date: 2004-06-21
Publication date: 2012-04-17
Anticipated expiration: 2024-06-21
Also published as: AU2004248855B2; AU2010241520B8; EP1648544A1; AU2010257238B2; AU2010201899B2; AU2004248855A1; AU2003903139A0; AU2004248855B8; WO2004112873A1; CN1809397B; US8006691B2; AU2010201899A1; EP1648544B1; AU2004248855C1; CN1809397A; EP1648544A4; US20080072900A1; CA2528314A1; AU2010241520A1; NZ544765A

Abstract

A flow generator and humidifier construction is described, including a flow generator (50) construction adapted to reduce noise output compared to known flow generators of comparable size. The flow generator includes a chassis (64) forming first and second muffler volumes and a venturi-shaped connection portion (137), and a metal/polymer composite material blower enclosure (70) which suppresses noise from the blower (90). The humidifier (150) has a water container (698, 699,700) which is adapted for drop in assembly in the humidifier base (602) so as to align with air inlet and outlet passages and is retained in sealing relationship with the air flow passages by engagement of the humidifier lid (648).

Description

TITLE OF THE INVENTION

BREATHABLE GAS APPARATUS WITH HUMIDIFIER
BACKGROUND OF THE INVENTION

1. Field of the Invention [0001] This invention relates to breathable gas supply apparatus, and particularly but not exclusively to such apparatus for use in Continuous Positive Airway Pressure (CPAP) treatment of conditions such as Obstructive Sleep Apnea (OSA) and other respiratory disorders and diseases such as emphysema. It will be described herein in its application to CPAP treatment Apparatus, but it is to be understood that the features of the invention will have application to other fields of application, such as mechanical ventilation and assisted respiration.

2. Description of Related Art J00021 CPAP treatment of OSA, a form of Noninvasive Positive Pressure Ventilation (NIPPY), involves the delivery of a pressurised breathable gas, usually air, to a patient's airways using a conduit and mask. Gas pressures employed for CPAP
typically range from 4 cm H2O to 28 cm H2O, at flow rates of up to 180 L/min (measured at the mask), depending on patient requirements. The pressurised gas acts as a pneumatic splint for the patient's airway, preventing airway collapse, especially during the inspiratory phase of respiration.

[0003] CPAP machines comprising an air flow generator for supplying pressurised air to the patient are known, and over recent years there has been commercial imperative for more compact CPAP machines. However, in seeking to reduce the size of the CPAP machines there has been a trade-off between reduced size on the one hand and reduced performance and/or increased noise on the other, for example Malinckrodt/Tyco/Puritan Bennett `Goodnight' Series.

[0004] The advantages of incorporating humidification of the air supply to a patient are known, and CPAP machines are known which incorporate humidifying devices, either separately from the flow generator or integrated therewith. An example of an integrated flow generator/humidifier unit is the ResMed S7 sold by the present Applicant.

[0005] Another problem with some flow generators is extensive use of foam in the air path for sound absorption. The foam can degrade with time.

SUMMARY OF THE INVENTION

[0006] One of the objects of the invention is to provide a simple and compact breathable gas supply apparatus incorporating a humidifier which is simple and economic in its construction, compact, and easy to use. Other objects and advantages of the invention will be described throughout the specification.

[0007] It is to be understood that apparatus described herein contains a number of advances on the prior art, many of which are independent inventions, although they contribute together to the realisation of the general object expressed above.

[0008] The apparatus described herein incorporates novel aspects of architecture of both the flow generator and the humidifier, and of their integration, which contribute to a reduction in size compared with known units having similar performance. Techniques for noise reduction and damping are described which enable such a smaller machine to have noise performance which is at least as good as known larger machines.

[0009] The apparatus described herein achieves full integration of the humidifier with the flow generator, in the sense that air flow, electrical and, if required, data connection between the flow generator and the humidifier are provided automatically upon the physical engagement of the two devices, without the need for any other process of interconnection.

[0010] In such an integrated device, provisions to guard against flowback of water from the humidifier tank to the flow generator are important, and novel sealing arrangements, and novel arrangements for minimising the occurrence of flowback while at the same time improving the uptake of water vapour in the humidifier are also described. The humidifier is readily detached and replaced on the machine, and has very few parts to be disassembled during cleaning.

[0011] Also described herein are improved, modular, devices for enabling data connection with the apparatus, including the connection of data storage devices such as memory cards, smart cards, communication ports and the like to be selectively attached by the user or by medical personnel.

[0012] Another aspect of the invention is to reduce or eliminate the use of foam in the air path.

[0013] In one form, the invention provides a flow generator unit for delivering breathable gas to a patient, including:
a flow generator case;
a powered gas flow generator within the case;
a power supply unit adapted for drop-in assembly in said case, said power supply unit including a printed circuit board, a power input connector rigidly attached to said printed circuit board and a power output connector, and a power supply unit mounting for mounting said power supply unit in said case such that said power input connector aligns with a power input port of said case.

[0014] A further form of the invention provides a blower enclosure for a now generator used in delivery of breathable gas to a patient, said blower enclosure including a metal container overmoulded with an acoustically damping polymer lining.

[0015] A further form of the invention provides a blower enclosure for a flow generator used in delivery of breathable gas to a patient, said blower being adapted to reduce noise from the enclosed blower, said enclosure comprising:
a cavity within a chassis of the flow generator, the cavity defined by side walls and base, the enclosure being adapted to receive and mount a blower in said cavity and a lid adapted to be mounted on said chassis so as to form a top surface of the cavity, wherein at least one of the chassis and lid is moulded from a composite comprising a metal and a plastic.

[0016] A further form of the invention provides a blower for a flow generator used in delivery of breathable gas to a patient, said blower comprising an electric motor with a shaft, an impeller adapted to be mounted on the shaft, and a volute having an air-inlet and an air-outlet, the volute defining a chamber in which a flow of air at pressure is developed, the volute being moulded from a composite comprising a first plastic material and a second plastic material, the first plastic material being generally rigid and the second material being generally elastomeric.

[0017] Preferably, wherein the first plastic material is overmoulded with the second plastic material.

[0018] Preferably, the volute comprises an upper volute and a lower volute, the lower volute incorporating the air-inlet. Preferably also, the lower volute includes feet moulded from the second plastics material.

[0019] Preferably, the upper volute incorporates the air-outlet. Preferably also, the upper volute includes a seal constructed from the second plastic material and which in use is adapted to provide a seal between the upper and lower volutes.

[0020] In one embodiment the upper and lower volutes are adapted to be snap-fitted together.

[0021] A further form of the invention provides a flow generator case for a flow generator used in delivery of breathable gas to a patient, said flow generator case comprising a shell of rigid plastics overmoulded with an elastomeric lining.

[0022] Preferably, said elastomeric lining forms external feet of said flow generator case.

[0023] A further form of the invention provides a fan support arrangement for a flow generator used in delivery of breathable gas to a patient, including a fan housing containing a motor and fan, said support arrangement including a plurality of mounting springs, wherein said springs, fan housing, motor and fan form a spring system having a natural resonant frequency less than one tenth of the frequency of a lowest operating speed of said fan.

[0024] A further form of the invention provides a flow generator unit for delivering breathable gas to a patient, including a flow generator case having an air outlet, a fan volute contained within said case, further including a flexible tube connecting an outlet of said fan volute to said air outlet, said flexible tube having two or more corrugations therein.

[0025] A further form of the invention provides a flow generator and humidifier combination for continuous positive airway pressure treatment of a patient, including a flow generator and a humidifier removably attached to the flow generator, wherein said flow generator includes a humidifier attachment detector including an optical transmitter and an optical sensor and wherein said humidifier includes an optical path connector which, when said flow generator and humidifier are attached, completes an optical path between said optical transmitter and said optical sensor.

[0026] A further form of the invention provides a muffler arrangement in an air flow path of a flow generator used in delivery of breathable gas to a patient, including a first muffler volume, a second muffler volume and a connecting portion linking said first and second muffler portions, wherein said connecting portion is narrow relative to said muffler portions and includes a lead-in portion which narrows in a direction away from said first muffler portion.

[0027] Preferably said connecting portion includes a venturi.

[0028] A further form of the invention provides a handle assembly for a flow generator used in delivery of breathable gas to a patient, including a flow generator case, a handle including a pair of attachment arms, each attachment arm having a projection received in a respective track of said case, and a handle retention member which attaches to said case to retain said handle projections against travel along said track.

[0029] A further form of the invention provides a method of attachment of a handle to a flow generator case, said handle including a pair of attachment arms, each attachment arm having a projection received in a respective track of said case, including the steps of sliding said handle projections along respective of said tracks and attaching a handle retention member to said case to retain said projections against travel along said respective tracks.

[0030] Preferably, said sliding of said handle projections along said track occurs without substantial distortion of said attachment arms.

[0031] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a humidifier case, a water container, a heater located in heat transfer communication with said water container, a gas flow path including a gas inlet, a humidified gas outlet and an intermediate gas flow path which contacts the gas with water vapour from said container, further including a drainage opening adjacent said heater allowing drainage of water past the heater to exit said humidifier case.

[0032] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a humidifier case, a water container, a heater pad located in heat transfer communication with said water container, a gas flow path including a gas inlet, a humidified gas outlet and an intermediate gas flow path which contacts the gas with water vapour from said container, wherein said heater pad has an upper heating surface and a peripheral heating surface which includes a side wall of said heater pad, and wherein a heat transfer surface of said water container is shaped to correspond to said heater pad so as maintain close heat transfer communication with said upper heating surface and peripheral heating surface of said heater pad.

[0033] Preferably, said water container defines a water volume which extends both above and below a level of said heating pad upper heating surface.

[0034] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a humidifier case having a hinged lid, a water container adapted for drop-in assembly in said case, a heater in heat transfer communication with said water container, a gas flow path including a gas inlet, a humidified gas outlet and an intermediate gas flow path which contacts the gas with water vapour from said container, wherein said water container has a gas passage inlet communicating with said gas flow path, said humidifier further including a gas passage inlet seal for sealing connection said gas passage inlet to said gas flow path, wherein said sealing connection is actuated by drop-in assembly of said water container and hinged closing of said lid.

[0035] Preferably, said gas passage inlet is located on a rear face of said water container and aligns with a gas passage aperture on an opposed face of said case.

[0036] A further form of the invention provides, in a humidifier assembly for a now generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tub having an inlet, a base having a blower outlet and a water-tub-receiving-portion, and a hinged lid with an engagable locking mechanism, a method of forming a seal between the water tub inlet and the blower outlet of the base comprising the steps of:
placing the water tub in the tub-receiving-portion of the base so as to position the inlet and the outlet adjacent one another;
closing the hinged lid; and engaging the locking mechanism.

[0037] Preferably, the blower outlet includes front-facing seal forming surface, and the step of placing the water tub in the water-tub-receiving portion of the base further includes the step of placing the water tub against the seal forming surface of the blower outlet.

[0038] A further form of the invention provides, in a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tub having an air outlet and an hinged lid with an engagable locking mechanism and an air delivery portion adapted to mate with an air delivery conduit so that the supply of breathable gas can be provided to a patient interface, a method of forming a seal between the water tub air outlet and the air delivery portion comprising the steps of:
closing the hinged lid; and engaging the locking mechanism.

[0039] Preferably, the hinged lid has an underside, and the underside includes a seal forming surface comprising a removably attachable gasket.

[0040] A further form of the invention provides a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tub having an air inlet and an air outlet, a humidifier base having a blower outlet and a water-tub-receiving portion, and a lid having an air delivery portion adapted to mate with an air delivery conduit so that the supply of breathable gas can be provided to a patient interface, wherein said water-tub-receiving portion and water tub have complementary formations adapted to guide drop-in positioning of said water tub to align said air inlet with said blower outlet.

[0041] Preferably, said complementary formations further guide positioning of said water tub to align said air outlet with a position of said air delivery portion of said lid when said lid is closed.

[0042] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a humidifier case having a lid, a water container within said case, a heater in heat transfer communication with said water container, a gas flow path including a gas inlet, a humidified gas outlet in said lid and an intermediate gas flow path which contacts the gas with water vapour from said container, and a gas outlet seal operatively associated with said lid whereby closing said lid creates a sealed communication between said humidified gas outlet the seal and a gas' space of said water container.

[0043] Preferably, the humidifier further includes a gas passage seal attached to the underside of said lid cooperating with a surface of said water container to form a sealed gas passage between a gas passage inlet and a gas inlet to said gas space.

[0044] Preferably also, said gas outlet seal and said gas passage seal are integrally formed.

[0045] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a water container, a heater in heat transfer communication with said water container, a gas flow path including a gas inlet, a humidified gas outlet in said lid and an intermediate gas flow path which contacts the gas with water vapour from said container, wherein said intermediate gas flow path includes a gas passage between a gas passage inlet and a gas inlet to said gas space, said gas passage having a floor sloping downwards from said gas passage inlet to said gas inlet.

[0046] Preferably, said gas passage includes a drainage portion below a level of the gas passage inlet, being a forwardmost portion of said gas passage having a front wall below the level of the gas passage inlet.

[0047] A further form of the invention provides a humidifier for delivering humidified breathable gas to a patient, including a water container, a gas flow path including a gas inlet, a humidified gas outlet in said lid and an intermediate gas flow path which contacts the gas with water vapour from said container, wherein said gas flow path is adapted to introduce said gas into a headspace of said water container with a swirling motion.

[0048] Preferably, said intermediate gas flow path includes a container air inlet adapted to introduce gas generally tangentially into said container headspace.

[0049] Preferably also, said intermediate gas flow path includes an arcuate gas flow path leading to said container air inlet, and further includes a container air outlet positioned generally centrally of said headspace.

[0050] A further form of the invention provides a control circuit for a humidifier for delivering humidified breathable gas to a patient, including a user operable control for selecting a desired gas humidity setting and a heater control circuit for determining a target heater temperature corresponding to the humidity setting and controlling a heater to attain said temperature, wherein said user operable control includes an off setting for which said heater control selects a target heater temperature less than a lowest operating temperature of said humidifier.

[0051] A further form of the invention provides a control circuit for a humidifier for delivering humidified breathable gas to a patient, including a user operable control for selecting a desired gas humidity setting and a heater control circuit controlling a heater current to a value corresponding to the humidity setting, said user operable control including setting a reference voltage in response to said user operable control and amplifying said voltage to control said heater current.

[0052] A further form of the invention provides a flow generator for delivering breathable gas to a patient, including a processor, a timer, user input means and a display, said processor being programmed to receive a reminder request input and to generate a reminder display at a time specified in said reminder request input.

[0053] Preferably, said processor is adapted to cancel a reminder request upon receiving a cancellation input from said user input means.

[0054] Also described herein are improved, modular, devices for enabling data connection with the apparatus, including the connection of data storage devices such as memory cards, smart cards, communication ports and the like to be selectively attached by the user or by medical personnel.

[0055] A further form of the invention provides a modular data or electrical connector arrangement for a flow generator unit for delivering breathable gas to a patient, including:
a flow generator case including an aperture;
a gas flow generator;
a control circuit for said flow generator, said circuit including a connector positioned to be accessible through said aperture for data or electrical communication with an external device; and a plurality of closure modules each adapted to attach to said case to cover said aperture, at least one of said closure modules including an internal connector adapted to connect with said control circuit connector, an external data or electrical port adapted for connection to said external device and a data or electrical pathway between said internal and external connectors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The various aspects of the invention will now be described with reference to the accompanying illustrations, which show a presently proposed embodiment.

[0057] In the drawings:

[0058] Figure 1 is a general view of breathable gas apparatus embodying the various features of the invention;

[0059] Figure 2 is a general view of the flow generator of the apparatus;

[0060] Figure 3 is a general view of the humidifier unit;

[0061] Figure 4 is a cutaway view of the flow generator;

[0062] Figure 5 is an exploded view of components of the flow generator;

[0063] Figure 6 is a vertical transverse cross-section of the flow generator;

[0064] Figure 7 is a more detailed illustration of the bottom case and power supply of Figure 5;

[0065] Figure 8 is a more detailed illustration of the chassis, chassis lid and fan housing of Figure 5;

[0066] Figure 9 is a more detailed illustration of the PCB, top case and exterior fittings of Figure 5;

[0067] Figure 9A is a schematic vertical cross-section detail of the connection of the handle to the flow generator top case;

[0068] Figure 10 is an underneath view of a chassis forming part of the flow generator;

[0069] Figure 11 is a vertical cross-section of the chassis through a venturi passage connecting muffler cavities of the flow generator;

[0070] Figure 12 is a general view of a fan forming part of the flow generator;

[0071] Figure 13 is a vertical cross-section showing the fan mounting arrangement;

[0072] Figure 14 is an exploded view of a humidifier adapted for use with the flow generator of Figure 5;

[0073] Figure 15 is a rear view of the humidifier assembly;

[0074] Figure 16 is a perspective of a seal for the air flow path;

[0075] Figure 17 is an underside perspective of the humidifier lid of Figure 14;

[0076] Figures 18 and 19 are respectively a perspective and a detail cross section of the humidifier lid seal of Figure 14;

[0077] Figures 20 and 21 are respectively a perspective and a longitudinal cross section of the humidifier tub lid of Figure 14;

[0078] Figure 22 is a graph of heater target temperature against humidifier setting;

[0079] Figure 23 is a schematic circuit diagram of a power control circuit to the humidifier heater;

[0080] Figure 24 illustrates reminder menus of the flow generator control; and

[0081] Figures 25 to 34 show various modular data connector arrangements;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0082] The illustrated apparatus comprises a flow generator 50 and a humidifier 150, shown in their assembled condition in Fig. 1, and separately in Figs. 2 and 3 respectively. As shown in Fig. 2, the flow generator engages with the separable humidifier at an engagement face 52, from which protrudes an air connector 53 for the delivery of air from the fan to the humidifier container, electrical connectors 54 for the delivery of power to the humidifier heater and an optical coupling transmitter 200 and sensor 201 described further below.

[0083] The face 52 also carries a pair of slots 55 which are engaged by corresponding tongues 156 provided on the humidifier engagement face 157 (Fig.
15) by which the flow generator 50 and humidifier 150 are connected together, as will be described in more detail below.

Flow generator

[0084] Externally, the flow generator 50 is also provided with an LCD screen 58 and associated keys 59 by which the user can set the operating parameters of the unit.
Flow generator case

[0085] The flow generator 50 has an external case of rigid plastics material moulded in two parts, a top case 60 and a bottom case 61. The lower edge of the top case 60 is stepped and flanged at 62 (Fig 9) to mate with the periphery of the bottom case 61.

[0086] With reference to Fig 7, the bottom case 61 of flow generator 50 has a shell 120 of rigid plastics material, such polycarbonate/ABS blend, forming the structure of the case, integrally overmoulded with a lining 121 of an elastomer such as a synthetic rubber or thermoplastic elastomer which forms the seal 63 between the top and bottom cases and the chassis 64 and also forms the external feet of the case (see Fig. 6). The lining 121 also covers the internal surface of the chassis-receiving cavity of the bottom case and the dividing wall 123 between the power supply cavity 65 and chassis-receiving cavity, the resulting composite of the rigid shell with elastomeric lining serving to reduce radiated noise levels from the flow generator by damping acoustic resonance of the walls.

[0087] Formed in the bottom case 61 by walls which join the outer wall of the case are the lower parts and of, respectively, a power supply cavity 65 and a first muffler cavity 134. The upper parts of these cavities are formed by the chassis 64, described below.

[0088] The first muffler cavity forms part of the air flow path from the air inlet 85 to the blower, receiving air from an air inlet path defined by the chassis 64, as described below.

[0089] The chassis 64 forms the blower or fan cavity 70, inlet and outlet air flow paths and the top of the power supply cavity 65. The fan cavity 70 includes a metal liner tub 73 insert moulded into the chassis as described below.

Flow generator chassis

[0090] The chassis 64 is formed with a peripheral wall 69 flanged around its lower edge to engage with the inner periphery of the overmoulded sealing flange 63.
The chassis 64 includes a downwardly extending fan cavity 70 in which is mounted the fan 90 described below. This cavity 70 is formed by moulded side walls 71 and base 72, which are formed by moulding inner and outer layers of thermoplastic around an inserted steel liner tub 73. The tub may be stainless steel, nickel plated mild steel or other suitable corrosion resistant metal. The fan cavity 70 opens to the upper surface of the chassis 64 to enable insertion of the fan 90, this opening being closed by a lid 74.

[0091] The density and stiffness of the steel tub creates a highly effective barrier to transmission of the motor and fan noise, while formation of the cavity 70 by insert moulding from differing materials provides very effective acoustic damping, as does the combination by co-moulding of the hard and soft plastics described already and further described below. In this aspect of the present invention, the use of co-moulding or overmoulding in the combination of materials of different, preferably widely different, stiffness and different, preferably widely different, density has been found to be particularly advantageous in providing acoustic damping.

[0092] Preferred materials for the chassis and liner tub are polypropylene thermoplastic for the chassis and metal, preferably steel (optionally stainless steel), for the liner tub. The applicant has found that by forming the fan cavity as a composite of metal and polymer - having a differential in density of greater than 5 times, preferably about 7-8 times, and also significantly different stiffness and damping properties - the resonance peaks of the composite structure are well damped so that noise generated by the fan is well-suppressed by the fan cavity construction.

[0093] It is especially preferred that the polymer for the chassis 64 be a glass fibre-filled polymer containing from 10-40%, and more preferably about 30%, glass fibre. The Applicant has found that the use of this material as a composite with a steel liner tub 73 gives both effective damping of fan noise and a good match in thermal expansion characteristics so that the composite material chassis performs well over a wide range of operating temperatures. Further, the Applicant has found that the use of glass fibres outperformed talc, bronze, glass bead filler materials for this purpose.

[0094] The top of the fan cavity is formed by the chassis lid 74, which is formed of an embedded steel insert overmoulded with elastomer to provide acoustic damping and sealing of the top of the fan cavity 70 A preferred polymer lining for the lid is an elastomer, for example of the same type used for the lining 121 of the bottom case.

[0095] Again, the use of a steel and polymer composite creates an effective and well-damped barrier to transmission of fan and motor noise.

Drop-in power supply

[0096] The upper part of the power supply cavity 65 is formed by a side wall 75 extending downwardly from the roof of the chassis 64, which sealingly engages the opposed wall of the lower portion of this cavity. Preferably, the lower wall is provided for this purpose with a co-moulded or overmoulded rubber sealing flange 76.

The power supply compartment is thus sealed against the ingress of moisture from the interior of the unit in the case of backflow from the humidifier. Similarly, the air path is sealed from the power supply compartment. The interior is at the same time acoustically sealed from the power supply cavity, which may not be completely sealed from the exterior, due to the necessity of providing mains power input and low voltage power output to the humidifier, via connectors 77 and 79 mounted in apertures 78 and 80 respectively in the rear and front walls of the cavity, and if necessary the venting of the compartment to outside air for cooling. This reduces assembly time and allows the overall device to be smaller.

[0097] With reference to Fig. 7, a power supply unit 124 is received in the power supply cavity 65, for providing electrical power for operation of the fan, control functions and the humidifier heater pad. The power supply comprises a printed circuit board 133, to which are directly attached by soldering or other suitable means a power inlet connector 77, a fan power outlet connector 126 for the fan motor and a humidifier power outlet 79. Each end of the power supply cavity 65 has mounting guides 136 for supporting the PCB of the power supply in an upright position so that installation of the power supply is achieved by drop-in assembly. By rigid attachment of the connectors by soldering direct to the PCB, the need for connection of wiring looms to the PCB is eliminated and the connectors align with respective ports in the bottom case 61 when the power supply is inserted.

PCB

[0098] With reference to Fig. 8, the fan 90 and fan housing 93, 94 fit into the fan cavity 70 of the chassis and connect to electrical connector 26 at the top of the power supply PCB. Elastomer overmoulding of the base 94 of the fan housing seals the housing, provides acoustic damping of the fan housing base and forms feet on the bottom of base to act as bump stops protecting the fan in case the unit is bumped or dropped.

[0099] As shown in Fig. 9, supported on the top of the chassis 64, in the space formed between the chassis and the top of the top case 60, is a printed circuit board 81 carrying the electronic control components of the unit. The printed circuit board 81 preferably includes an LCD display 58. Optionally, at the rear of the board an edge connector 1082 and a sliding connector 1082A may be accessible from a connector aperture in the rear of the case 60, providing for modular connector arrangements to be described in more detail below with reference to Figs 25 to 34.

Air inlet path and mufflers

[00100] Also provided in the rear wall of the top case is an air inlet 84, and this communicates with an air inlet passage 85 formed in the chassis above the roof of the upper portion of the power supply cavity 65, this passage in turn opening to first muffler cavity 134 surrounding the bottom of the fan cavity of the chassis.

[00101] The top case further defines an air inlet to the flow generator, and has a replaceable filter 129 of any suitable material, such as foam or fibre, and filter cover 130 fitted to the top case 60. An inlet wedge 131 serves as an airflow guide.
A blank cover 132 clips in place over apertures in the case which align with connectors 1082, 1082A to provide ports on the PCB for communications, etc. Further details of the communications and/other electrical ports in the flow generator case will be described later with reference to Figs. 25 to 34.

[00102] From the first muffler volume 134 under the fan cavity 70, inlet air passes through a connection passage 137 (Fig. 11) into a second muffler volume formed by the space between the fan cavity 70 and the fan.

[00103] The fan cavity and the space between the bottom case and the chassis thus form a pair of serially connected volume mufflers, with a restricted diameter passage therebetween. Noise attenuation produced by a muffler system is generally proportional to the ratio of a representative diameter of the muffler volume to that of the constriction, and thus an optimal muffler design must balance optimal noise attenuation against the constraints of available muffler volume - especially in a compact machine - and avoiding unacceptable air flow restriction through the constriction.

[00104] The Applicant has found that a favourable adjustment of this balance maybe achieved by forming the intermediate connecting passage 137 between the muffler volumes as a venturi, as shown in Figs. 10 and 11, with a relatively short, smoothly varying diameter lead in portion 137a at the end adjacent the first muffler, an intermediate constriction 137b and a gradually expanding lead out portion 137c at the downstream end. In this way, the muffler system can achieve the noise attenuation according to the representative diameter of the smallest diameter portion, with better pressure drop characteristics.

Fan

[00105] It will now be convenient to describe the features of the fan, which are shown in Figs. 12 and 13.

[00106] The fan 90 comprises a motor 91, preferably brushless DC motor, provided with a coaxial impeller 92, mounted vertically within a fan housing consisting of a cover 93 and a base 94. An air inlet 95 is provided in the floor of the base 94 on the impeller axis, and cavities in the cover and base form a volute 96 which leads from the impeller to an air outlet 97. The cover and base 93 and 94 are joined by means of slotted tabs 98 which extend upwardly from the base to snap over stepped ribs 99, the tabs 98 being further located by fitting between parallel ribs on the cover 93. The joint between the cover 93 and the base 94 is sealed by an elastomeric over-or co-moulded sealing ring 101.

[00107] The bottom surface of the fan housing base 94 is provided with radial stiffening ribs, and overmoulded to the base 94 is an elastomer damping member which covers that bottom surface between the ribs, and extends around the edge of the base by a flange portion and peripherally spaced tabs. By overmoulding to the rigid plastics base 94 an elastomer of much lower stiffness substantial acoustical damping is provided to the fan housing.

[00108] Moulded integrally with the rigid plastics portion of the fan housing base are feet 106 which extend proud of overmoulded elastomer member 103 to receive helical mounting springs 102 (Fig. 13), preferably of metal, by which the fan is mounted on the base 72 of the fan cavity.

[00109] The degree of size reduction which is an objective of the present invention requires great care to be taken to minimise the transmission of noise and vibration, particularly from the motor and the impeller of the fan 90. The mounting springs are therefore chosen to ensure minimal transmission of the vibration frequencies encountered during operation. This is achieved by choosing the springs with reference to the mass of the fan 90, such that the natural frequency of the system comprising the springs and the fan is less than. approximately one tenth of the shaft speed of the motor when running at its lowest operating speed.
[001101 The air outlet 97, upon the introduction of the fan into the fan cavity, is connected by means of a thermoplastic elastomer or silicone rubber coupling member 108 with an air passage which extends from the side wall of the fan cavity to a connecting nozzle 110 extending through an aperture provided for this purpose in the front face of the flow generator. It is preferred that the coupling member 108 includes at least two corrugations which provide flexibility to the connection and improved resistance against transfer of vibration from the fan to the flow generator case.
[00111] The fan 90 therefore floats within its cavity 70 in the chassis 64 with minimum acoustic. coupling to the remainder of the flow generator. The characteristics of the mounting springs and the coupling member 108 are chosen to minimise the transmission of characteristic vibration frequencies of the fan.
[00112] Further details- of the fan construction and fan mounting are described in 0520030168064 and W099/64747.

[00113] The illustrated flow generator . construction and materials.combinations are adapted to result in a compact CPAP flow generator unit' of similar performance and noise characteristics to larger units - eg. capable.of generating from 4-20crnH2O
pressure and a flow rate of 120 I/min and a total radiated noise volume of less than 33dbA, more preferably less than about 30dbA, when operating at 10 cmH2O - in a flow generator. unit having a total volume of about 2 litres or less.

Handle attachment [00114] A keypad 59, facia 127 and transport handle 128 attach to the top case 60.
[00115] With reference to Figs 9 and 9A, a novel and easily assembled handle attachment assembly is described and shown. The handle 128 has opposed arms with inwardly projecting pins 140 at their distal ends. ' The top case 60 includes a pair of chMmel-shaped tracks 141 with one open and one closed end, for receiving-respective of the pins. To assemble-the handle to the top case, the pins are inserted from the open ends of their respective channels and slid toward the closed ends. The facia 127 clips onto the top case 60, and includes projections 142 which trap the pins 140 in the end of their tracks 141.
[00116] The handle attachment configuration thus provides a quick and simple means of assembly without requiring flexing of the handle arms to locate the pins into small recesses as in the prior art.

Humidifier [00117] As shown in Fig. 14 to 21, the humidifier 150 comprises a base unit designed for simple attachment to and detachment from the flow generator 50, which forms a cradle for a water container which is in turn attachable to and detachable from the base unit.
[00118] The general arrangement of the humidifier components includes a base (rear cover 803 and front cover 602) onto which is fitted a heater comprising a heater plate (plate 632 with ceramic heater pad 800) which supports a water tub (tub base 698, seal 699 and tub lid 700) and a hinged humidifier lid 648 which seals against the tub lid 700 to form an air path into the tub through the tub lid.
[00119] The rear face of the base has a peripheral flange 153 which seats in a corresponding peripheral recess 113 surrounding the front face of the flow generator 50 when the two units are brought together by linear movement towards each other. A
latch 404 is held in place by latch retainer 404a to be moveable vertically and resiliently urged downwardly by spring 404b, so that the tongues 156 engage in the slots 55 and snap home to engage the two units by means of the downwardly extending fingers 158 at the ends of the tongues.

Coupling of flow generator and humidifier [00120] The PCB of the flow generator is provided at the end adjacent the humidifier with an optical transmitter 200 which emits a periodic flash of light from the end face of the flow generator case, and an optical sensor 201 to detect the presence or absence of the humidifier. The rear face of the humidifier contains a curved reflector 202 which, when the humidifier is attached to the flow generator, completes an optical path from the transmitter to the sensor so that the flow generator PCB detects the presence of the humidifier and may adjust the control algorithms accordingly.
[00121] The rear face of the base unit also carries a connector 162, in this embodiment a pair of flat male blade connectors, for engagement with a mating connector 114 on the front face of the flow generator, to provide power to the humidifier heater from the power supply in the power supply cavity 65.
Although not shown in the illustrated embodiment, the respective faces may also carry further interconnecting devices, where other electrical or data connections are required to be established between the flow generator and the humidifier or downstream devices including the air conduit or the mask. Such devices may take the form of optically coupled devices, or connectors of other suitable kinds.
[00122] The use of such an opto-coupling connector enables the implementation of a simple protocol for communications between the flow generator and the humidifier. For example, the current flow levels of the flow generator can be sent to the humidifier controller which then adjusts the operation of the humidifier according to a predetermined algorithm.
[00123] In the humidifier construction, the back cover 803 which fits to the rear of the front cover 602 provides the air, electrical and communications connections to the flow generator and provide support for a control PCB 804 and the catch assembly.
The catch assembly includes a latch 404 which is retained by a latch retainer 404a and spring 404b, and operates to attach the humidifier to the flow generator generally as described for the earlier embodiments. A control knob 805 on the top of the front cover 602 is connected to the PCB 804 to allow patient control over the degree of humidification.
[00124] There is also provided an aperture 264 (Fig. 15) for electrical connections between the humidifier and the flow generator, or for electrical and signal connections to the humidifier.
[00125] The air port 807 in the humidifier rear face mates with the outlet 110 of the flow generator.
[00126] An elastomer airway seal 722 fits between the front and back covers to connect the air port 807 in the back cover 803 to the aperture 626 of the front cover 602. The seal (shown in more detail in Figure 16) has an inlet connector portion 722a which connects to the flow generator output via the air port 807 formed in the back cover 803, and a peripheral seal portion 722b which extends about the aperture periphery at the front face of the cover 602. A wall portion 722c of the seal closes off a lower part of the aperture 626, leaving a smaller aperture 722d defined by the seal.
[00127] As a result, the airway seal 722 defines a closed passage from the circular air port 807 to the rectangular aperture 722d in the vertical wall of the front cover.

Heater pad [00128] The heater pad comprises lower and upper parts 806, 800 and a heater pad cover 632.
[00129] The heater pad cover 632 has an upper heating surface 634, a downwardly extending peripheral wall 636 acting as a further heating surface and a rear flange with a pair of attachment portions 640 for attachment of the heater pad to tubular protrusions 628 on the rear of the front cover 602.
[00130] The heater pad cover 632 is configured to accommodate, below the upper wall 634 and within bounds of the wall 636, a heater pad or other heating means such as an induction heater, for causing heating of the water in the humidifier water container.
[00131] The front of the heater pad cover 632 has a forwardly extending tab 646 of dog-legged shape, which extends to the front of the humidifier cradle front cover 632 to support the heater and also provide a catch for the humidifier lid 648.
Water Tub [00132] The water container consists of a water tub 698, seal 699 and tub lid 700.
[00133] The floor of the tub 698 is of complementary shape to the heater pad, and is formed of metal or other material suitable to conduct heat from the heater pad to the water in the tub. The floor has a generally horizontal portion 900 corresponding to the upper heating surface 634 of the heater pad and a U-shaped portion below the level of the heater pad upper surface, including a generally vertical heat transfer portion 902 below the horizontal portion corresponding to the peripheral heating surface. When the water container is placed in the humidifier cradle and the hinged lid 648 closed, the water tub base is held in close contact with the heater pad to transfer heat into the water in the tub.
[00134] By providing a part of the water tub volume and heat transfer surface about the periphery of the heater pad, a similar water volume and heating area to those in prior art humidifiers can be obtained in a more compact assembly.
[00135] As shown in Figure 20, the rear surface of the tub lid has an air inlet aperture 801 leading to an inlet end of the U-shaped air passage 718. When the humidifier lid 648 is closed, the tub 698 and tub lid 700 are pressed rearwards so that the peripheral seal 722b abuts the rear surface of the tub lid in a locus surrounding the rear opening of the inlet aperture 801, creating a sealed air path from the flow generator outlet to air passage 718 and into the headspace of the humidifier tub. This allows the humidifier tub to be removed for refilling and replaced without the need for a separate operation to connect the air flow.
[00136] With reference to Figure 21, the inside wall of the tub lid 700 has projections 802a, 802b which serve to limit the press fitting of the tub lid onto the tub base 698. One projection 802a is provided at the front of the tub, and further projections 802b, or sets of projections, are provided on opposed side walls of the tub lid, forward of the rear of the tub. This positioning of the projections 802b allows one-handed disengagement of the tub base and tub lid by squeezing together of the base and lid at their rear end, causing the connection to pivot about the side projections 802b and the tub and lid to separate at the front. The ability to separate these components one-handed is a feature of considerable utility, especially for stroke patients or other users with limited dexterity.
[00137] As best seen in Figs 20 and 21, the water container lid 700 has an air passage 718 formed as a U-shaped channel, leading to the humidified air entry aperture 720 into the headspace of the water container. The channel floor slopes down in the direction of air flow from the air inlet end to the end at which the air enters the water container. The water container lid also has an elliptical humidified air exit aperture 722. These air passages and apertures co-operate with the humidifier lid 648 when closed to define the air flow paths within the humidifier, as will be described below.

[00138] Water may be added to the water container via the air exit aperture while the tub lid is in place, or by removing the tub lid.
[00139] The tank is intended to be filled via the air outlet 722, and the apparatus may be provided with a filling bottle with a spout dimensioned for a convenient fit with that outlet. Such a bottle may be provided with a spout of the kind incorporating an air bleed passage which will allow the tank to fill to the correct predetermined height.
[00140] In alternative embodiments, other filling arrangements may be employed, for example by removing the tub lid. The correct filling height may also indicated by filling level graduations scribed or otherwise marked on the wall of the water tub.
[00141] A microswitch (not shown) or other sensing means may be provided to turn off power to the heater pad when the lid is opened, and/or when the water container is removed.

Humidifier lid and air flow paths [00142] Figures 17 to 19 show the underside of the humidifier lid 648 and the seal 676 which provides a seal to the tub lid 700 about the U-shaped passage 718 and the humidified air exit aperture 716. The seal 676 comprises an edge seal portion 676a and membrane portion 676b, as shown in Figures 18 and 19.
[00143] The lid 648 has an upper wall 650 and a front wall 652 which extends downwards, and outwardly, from the upper wall. The upper wall 650 has a recess at its rear side, such that the part of the upper wall and front wall 652 on each side of the recess constitutes a rearwardly projecting arm 656. At the rearmost extremity of each arm 656 there is an inwardly projecting hub 658. The hubs 658 are configured to be received in the sockets 622 of the humidifier front cover 602 such that each hub and its corresponding socket constitute a hinge connection, for attaching the lid 648 to the front cover.
[00144] During opening of the lid 648, it may be freely rotated about the hubs through greater than 90 until it reaches a maximum extent of normal travel.
The lid and front cover are configured such that, if the lid is then rotated further, the hubs pop out of the sockets 622. This may be achieved, as would be understood by a person skilled in the art, by providing suitable chamfers on the hubs and/or sockets, or other suitable formations on the lid or cover, so that the lid flexes to release the hubs from the sockets.
[00145] The lower edge of each arm 656 is shaped complementarily to the shape of the upper portion of the face of the front cover to accommodate that part of the arm when the lid 648 is in a closed position.
[00146] The lid 648 includes a humidified air outlet pipe 662 which passes through the upper wall 650 and extends upwards and forwards at an acute angle from the top of the upper wall, for attachment of a hose to supply humidified air to a patient. The pipe 662 continues below the lower surface of the upper wall 650 to define an elliptical rim 664.
[00147] Extending downwards from the lower surface of the upper wall 650 is a wall 666 which is configured to define a closed path and hence a U-shaped enclosed region 668 within the confines of the wall.
[00148] At the front extremity of the front wall 652, that is, adjacent the lower edge of that wall, there is provided a recessed notch 674 on the rear (inner) surface of that wall, for snap-fit engagement with the tab 646 of the heater pad cover to act as the catch for the lid. The lid may be opened by flexing the assembly to release the tab from the notch.
[00149] Attached to the lid 648 is an elastomer lid seal 676, which is illustrated in Figures 18 and 20. The edge seal portion 676a of the lid seal includes a channel 676c which fits over the wall 664 and rim 666 on the bottom of the lid 648, and a curved sealing flange 676d which seals against the top surface 'of the tub lid, so that the space between the U-channel 718 on the tub lid and the seal membrane forms an inlet air passage of the tub, and the air outlet aperture 722 of the tub lid communicates via the elliptical. opening 676e in the lid seal to the air outlet pipe 662 of the humidifier lid 648. This is achieved without the need to connect and disconnect air tubes to remove the water container.
[00150] As the air supplied from the flow generator is under pressure, this pressure assists the sealing flange 676d of the sealing member 676 to create a firm seal around the recess 718 by forcing the extension portion outwards and downwards.

A similar effect is created on the seal surrounding the elliptical aperture 716 in the tub lid due to the pressure of the air exiting the water receptacle.
[001511 Once the air from the flow generator passes into the water container, the air then travels across the surface of the water so that the air becomes humidified.
The heating of the water by the heating pad enhances this humidification. The air then exits the water container through the outlet opening 716 to the air outlet pipe 662, which is in turn attached to a suitable hose (not shown) for supplying the humidified air to a patient.
[001521 By providing the air inlet to the water tub headspace via an arcuate path, the air mass within the container is caused to swirl and thus enhance the uptake of water vapour from the water contained in the tub.
[001531 The enhanced uptake of water vapour achieved by inducing the swirling of air as it passes through the tank enables, in an alternative embodiment of the invention, the elimination of the heating of the water in the tub. In such an embodiment the heating element and its controls, and the heat transfer components including the heating plate and the metal tank base are eliminated, and the humidifier becomes a simpler, passive, device.
[001541 A humidifier assembly in accordance with the present invention has a number of advantages over the prior art. One advantage relates to convenience of use.
Convenience of use is important for all patients, especially those who have poor dexterity.
[001551 The base of the humidifier assembly includes a generally "negative" U-shaped channel. The bottom portion of the water tub has a corresponding "positive"
U-shape. The outer wall of the U-shape is sloping, whereas the inner wall is generally vertical. Because the base and water tubs have complementary configurations, placing the water tub generally in the correct position means that it will to some extent self-align into the correct position, which as described below, is a sealing position.
[001561 A water tub according to the present design can be easily placed in a sealing position without requiring a patient to connect small fiddly tubes such as used in the prior art. An aspect of this is that a seal is provided by placing a generally flat surface such as the rear of the water tub, or the top surface of the water tub, against respective silicone gaskets that present a corresponding flat surface. The respective seals are formed when the two flat surfaces contact. Thus the humidifier assembly has a very convenient "drop-in" configuration.
[001571 The water tub is held in position by the simple motion of swinging the pivoting lid through approximately 90 from fully open to closed. The lid is locked in position via a robust mechanism which provides and audible and reassuring "click"-sound when engaged. Whilst in the preferred embodiment, a pivoting movement is used for the lid, other movements are contemplated including sliding and translation.
[001581 The lid of the humidifier assembly includes an air delivery tube connector, which in a preferred form is generally cylindrical. Connection of the air delivery tube to the lid can be achieved regardless of whether the water tub is in position. This arrangement means that the water tub can be removed and refilled with water if necessary without requiring disengagement of the air delivery tube from the humidifier assembly.
[001591 The illustrated humidifier construction provides a compact humidifier adapted for ease of manufacture and use, and further provides protection against backflow of water into the flow generator when the humidifier and flow generator units are assembled together. Backflow protection is provided by the sloping floor of the air passage and the location of the air inlet aperture 801 and the aperture 722d in the seal 722 relative to the air inlet 720 from the air passage 718 into the headspace of the humidifier tub 698. In particular, if the tub is overfilled while in its horizontal position, the water will flow back along the U-shaped air passage 718 only as far as its forwardmost portion, which has a front wall 717 lower than the air inlet aperture 801, and will drain towards the front of the machine. If the machine is tipped up onto its rear, the water will be prevented from flowing back along the air passage from the tub to the air inlet 801 as the intermediate portion of the air passage 718 will be above the level of the aperture 720. The water will then flow back into the tub once the machine is righted.
[001601 If the machine is tipped onto its side, either the air inlet aperture 720 or the air inlet 801 will be above the water level and thus water should not flow back into the low generator. Again, any water which escapes the tub will flow back into the tub once the machine is righted.

[00161] If desired, further security against backflow can be provided by locating a non-return valve at an appropriate point, for example a flexible membrane supported in the mouth of the humidifier air inlet.
[00162] In addition to those features and advantages already described, the components and features of the humidifier according to the present embodiment have various advantages.
[00163] By providing the top seal to the water receptacle as part of the humidifier lid, improved simplicity of use is achieved while minimising the risk of spillage of water. In addition, the contour of the lid seal is adapted to collect condensation which may form in the lid cavity and the headspace of the water receptacle, preventing backflow of this condensation to the flow generator when the lid is opened.
[00164] Furthermore, the configuration of the front and back covers of the humidifier and of the heater pad is adapted to allow fitting together in a vertical orientation, to minimise the need for reorientation during assembly of the humidifier unit on the production line.
[00165] In addition, the resilience of the connection between the lid and the water receptacle, provided by the lid seal, is adapted to maintain downwards pressure on the water receptacle when the lid is closed, to maintain good heat-transfer contact between the base of the water receptacle and the heater pad without the added complexity and expense of spring-loaded mounting of the heater pad.

Humidifier power supply [00166] The humidifier is provided with a control knob allowing adjustment of the humidity of the air supply to the patient. With increasing humidity setting, the temperature of the water container is increased by providing increased power to the heater, to raise the humidity of the air leaving the humidifier. The control knob may have a smoothly variable control, or a series of discrete humidity settings, and will have an `off' setting where no power is supplied to the heating pad. The correlation between the humidity setting and the power to the heater is controlled by a circuit on the PCB 804.

[00167] Fig. 22 is a sketch of a preferred calibration curve of target water container temperature (y axis) against humidity setting (x axis), including upper and lower tolerances.
[00168] At the left hand end of the correlation curve, corresponding to the low humidity settings and the off position of the control knob, the heater control selects a very low target heater temperature - less than ambient temperature, and preferably lower than the lowest operating temperature of the humidifier. In this way, the heating is turned off when the control knob is in its off position, while allowing use of a less expensive potentiometer without an integral off switch or a separate on/off switch. The mounting of the control knob mechanism may provide a tactile `click' at the off position of the control knob, to confirm to the user that the heater is turned off.
[00169] Fig 23 is a circuit diagram of the humidifier control circuit for controlling the water temperature, including a potentiometer POT1 actuated by the control knob 805 and an operational amplifier OA1 providing power to the heater 800.
[00170] A potentiometer may be used in series with the heating element to set the operating temperature. However, this may result in large heat losses through the potentiometer as in the following equation P=V2/R
where V = the supply voltage and is normally fixed and R= RH + RP
where RH is the resistance of the heater and is fixed and RP is the resistance of the potentiometer which is variable and provides the temperature control. The current is:
I = V/R, and the proportion of heat through the potentiometer is 12*RP = RP
*V2/
(RP+ RH)2 . The remainder of the heat is used by the heater element to heat the water.
[00171] These heat losses in the potentiometer require large heat dissipation surfaces to prevent overheating.
[00172] In the present embodiment, the potentiometer is used in the control path of a semiconductor arrangement to set the operating temperature. This substantially reduces the current through the potentiometer because the potentiometer now only carries a semiconductor control current rather than the load current required to drive the heater element.

[00173] In a preferred embodiment, the potentiometer is used in conjunction with a temperature sensing element to control an operational amplifier which drives the heater directly or through a high current semiconductor switch.
[00174] Figure 23 shows an arrangement for controlling temperature via an operational amplifier OAl.
[00175] The operational amplifier nl has a pair of inputs, V+ being an adding input and V- being a subtracting input. The output of the amplifier is proportional to the difference between the voltages on the inputs V+ and V-.
[00176] Input V- is connected to a reference voltage determined by the ratio of resistors R21 and R17;
Vref = Vs*Rl2/(Rl2+R17) [00177] The temperature of the water is sensed by temperature sensitive resistive element, thermistor TH1, and the operating point is set by potentiometer POT1. The operational amplifier input V+ is connected to the. junction of R106 and thermistor TH1. The operational amplifier switching threshold is determined by the ratio of the resistance of the potentiometer POT1 plus resistor R106 to the resistance of the resistance network formed by thermistor TH1 plus resistor R11 in parallel with resistor R10 plus resistor R10 equals the ratio of resistor R17 to resistor R21. That is, the operational amplifier switches when the junction between the thermistor TH1 and resistor R106 crosses over the potential at V-.
[00178] The operational amplifier is powered from supply points Vss and Vo, so the drive current does not pass through the potentiometer. Vss may be the same as Vs, and Vo may be the same as Ov. The operational amplifier may drive the heater element directly or it may control a power transistor which drives the heater element.
[00179] This arrangement significantly reduces the dissipation through the potentiometer, allowing a smaller potentiometer, with smaller cooling needs, to be used. The arrangement is also well adapted for use in implementing the `soft' off setting arrangement described above with reference to Fig. 22.

Reminder Menu [00180] Fig. 24 is a flowchart of a Reminder menu to set a number of reminders to alert the patient to specific events; for example, when to replace their mask, when to insert a Data Card (if their device is Data Card enabled) and so on. It can also be used to set special customised reminders.
[00181] When a reminder is due, a message is displayed on the LCD and remains whenever the device is not delivering therapy. The backlight on the LCD
flashes when a message is displayed. If more than one reminder for a patient is scheduled for the same date, all scheduled reminders are displayed during that day. A
patient can clear a message by pressing the LEFT key (or inserting a Data Card, in the case of the Data Card reminder).
[00182] The default setting for all reminders is that they are disabled. To use the reminder menu, the patient enters the Reminder Menu from the standby screen by pressing LEFT and DOWN for at least three seconds.
[00183] Fig. 24 summarises the Reminder Menu screens:
[00184] REPLACE MASK - to set a timed reminder to remind a patient when they need to replace their mask. The patient can press the LEFT (clear) key to remove the message from the LCD.
[00185] CALL PROVIDER - to set a reminder for the patient to phone the therapist at a certain time; for example,to discuss how their therapy is going. The patient can press the LEFT (clear) key to remove the message from the LCD.
[00186] INSERT CARD - if a patient's flow generator. is Data Card enabled, the therapist can set a timed reminder on the flow generator to remind them that they need to insert a Data Card to transfer patient data. This enables the therapist to establish compliance. The patient should actually insert the Data Card in order to clear the message from the LCD. (They can also press the LEFT (clear) key to remove the message.) [00187] REPLACE FILTER - to set a timed reminder to remind the patient when to replace the air filter. The patient can press the LEFT (clear) key to remove the message from the LCD.
[00188] Figs. 25 to 32 are rear views of the flow generator, showing various forms of modular data connections foreshadowed earlier, utilising the slot 83 in the rear of the flow generator housing.
[00189] With reference to Fig. 25, the slot 83 is provided in the wall of a rectangular recess 1115. An arcuate depression 1123 is provided in the upper surface of the unit above the recess 1115 to facilitate removal of closure elements from the depression, as described below.
[00190] At the rear of the printed circuit board 81, an edge connector 1082 and a sliding connector 1082A are aligned with and accessible through the connector slot 83 in the rear of the case 60, providing for the modular connector arrangements to be described in more detail below.
[00191] Where, as shown in Fig. 26, the flow generator in question is not intended to be employed with any data connection, the slot 83 is closed off by a blank closure element 132, shaped to fit into the recess 1115. The closure element is shown in more detail in Fig. 27. This element snaps into the recess by means of lower tabs 1118 and an upper tab 1119 which fit corresponding depressions such as 1122 in the walls of the recess 1115, to close the slot 83 and conform to the contours of the surrounding surface of the unit.
[00192] Complementarily shaped closure elements can be provided for the reception of different kinds of data devices. Shown in Fig. 28 is an element 11 16a provided with a slot for the reception of a smart card 1120. The element 11 16a or the printed circuit board itself may carry the necessary smart card socket.
[00193] Shown in Fig. 29 is a closure element 1116b provided with a DB type data socket. In this case the element 1116b is contoured to provide a lower front recess 1121 to facilitate gripping of the associated plug. A cross-section of a modified form of this arrangement is shown in Fig. 29A, illustrating the connection between the internal connector 1086 of the element 1116b and the edge connector 1082 of the PCB, and the external DB9 connector 1088.
[00194] Other forms of element 1116 can be provided to enable the connection of devices such as memory cards and pre-programmed devices as required. This facility furthermore enables a wide range of devices to be integrated with the apparatus in modular fashion, for example a clock display which may utilise the system clock contained in the flow generator controller, a voice activation unit, oximetry, ECG and other diagnostic aids, a sound recorder, a light.
[00195] Figs. 30 to 32 are a series,of rear perspective views of the flow generator, illustrating one embodiment of the modular data connector arrangement.

Fig. 33 shows the front, inner surface of the USB closure element module, and Fig. 34 is a vertical cross-section of the flow generator.
[00196] Fig. 30 shows the slot 83 open, exposing the edge connector 1082 and sliding connector (not visible in this view) at the rear of the flow generator PCB 81.
The connectors 1082, 1082A comprise a plurality of electrical contacts for carrying data and/or power between the PCB and an external device.
[00197] Fig 31 shows the arrangement of Fig. 31 where no data connection is required, with the slot covered by a blank closure element 132 generally as described above with reference to Figs 25 to 27.
[00198] Fig. 32 shows a removable closure element module 11 16c carrying a standard universal serial bus (USB) port 1084 on its rear surface. The element 11 16c incorporates an electrical/data pathway to an electrical connector 1090 at its forward, inner surface (Figs. 33 and 34) adapted to connect with all or selected ones of the contacts of the PCB connector 1082 for electrical and/or data transmission.
The closure module 1116c has internal electrical components completing a data and/or electrical pathway between its internal and external connectors so that the module acts as an adaptor between the PCB connector and a standard USB port.
[00199] By providing the modular data connection arrangements as described above, in which a plurality of interchangeable connection modules fit to one or more fixed, standard connectors on the PCB, the cost and size of the flow generator unit may be reduced as the unit may be provided with only those connectors which are needed by that patient, and additional connector modules supplied only if the need arises. Furthermore, the arrangement facilitates upgrade of the data connection arrangement of the flow generator to keep up with technological advances or changes in global data connection standards.
[00200] In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed"
sense, that is the sense of "consisting only of'. A corresponding meaning is to be attributed to the corresponding words "comprise, comprised and comprises where they appear.
[00201] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof.
The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. It will further be understood that any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates.

Claims

CLAIMS:

1. Apparatus for the treatment of obstructive sleep apnea, comprising:
a continuous positive airway pressure device; and a humidifier including:
a humidifier base, a humidifier lid movable between closed and open positions while connected to the humidifier base, a removable humidifier tank having a tank lid including an outlet, said humidifier lid being adapted to seal around the outlet of the tank lid when the humidifier lid is in the closed position, and a humidifier heater plate;
the continuous positive airway pressure device and the humidifier are releasably connected by a latch;
the humidifier lid includes an air delivery portion adapted to mate with an air delivery tube;
the humidifier lid and the humidifier base are connected by a hinge adapted to allow the humidifier lid to rotate between the closed position and an open position;
the humidifier lid and the humidifier base include a locking mechanism adapted to releasably hold the humidifier lid in the closed position;
the humidifier base is adapted to receive the humidifier tank when the humidifier lid is in an open position and to locate the humidifier tank in heat transfer communication with the humidifier heater plate, and to establish a sealed gas flow path between the continuous positive airway pressure device and the air delivery portion of the humidifier lid when the humidifier lid is in the closed position.

2. The apparatus of claim 1 wherein the humidifier base includes a first gas flow path between the continuous positive airway pressure device and an interior of the humidifier tank, and a second gas flow path extending from the interior of the humidifier tank and through the humidifier lid.

3. A humidifier comprising:
a humidifier base including a latch adapted to releasably engage the humidifier with a continuous positive airway pressure device;
an air inlet adapted for sealable connection to an outlet of the continuous positive airway pressure device and being further adapted to receive a supply of air at positive pressure from said continuous positive airway pressure device through said inlet;
a heater plate;
a water tank adapted to receive the supply of air at positive pressure and adapted to be in heat transfer communication with the heater plate, said water tank having a water tank lid with an outlet;
a humidifier lid connected to the humidifier base to move between open and closed positions, the humidifier lid having an air outlet adapted to mate with an air delivery tube to deliver the supply of air at positive pressure to a mask, said humidifier lid being adapted to be in sealing contact with a surface surrounding the outlet of the water tank lid when the humidifier lid is in the closed position; and wherein said humidifier is constructed and arranged to removably locate the water tank without disconnection of the air delivery tube.

4. A humidifier comprising a removable water tank having a water tank lid with an outlet, a humidifier base having a water tank receiving portion; and a humidifier lid having an outlet adapted to mate with an air delivery tube, the humidifier lid being connected to the humidifier base such that the humidifier lid is movable between a closed position and an open position while connected to the humidifier base;
wherein the humidifier lid is adapted to seal against a surface surrounding the outlet of the water tank lid such that the humidifier includes a sealed air flow path extending from the water tank and through the outlet of the humidifier lid when the humidifier lid is in the closed position.

5. The humidifier of claim 4 wherein the humidifier lid is a hinged lid.

6. The humidifier of claim 4 or 5 further comprising hinges to connect the humidifier lid to the humidifier base.

7. A breathable gas supply apparatus for treatment of respiratory disorders comprising:
a continuous positive airway pressure device adapted for releasable connection to a humidifier; and a humidifier comprising:
a humidifier base having an aperture adapted to receive a supply of breathable gas from the continuous positive airway pressure device;
a first seal extending about the aperture;
a removable water tank having an air inlet and an air outlet, and respective surfaces surrounding the air inlet and air outlet, the surface surrounding the inlet being flat, the water tank having a water tank lid including an outlet;
a humidifier lid with an air delivery portion adapted to mate with an air delivery tube so that the supply of breathable gas can be provided to a patient interface;
the humidifier lid being adapted to seal around the outlet of the water tank lid when the humidifier lid is in a closed position, via a second seal located on an underside of the humidifier lid;
wherein the first seal is adapted to be in sealing relationship with the flat surface surrounding the air inlet of the water tank when the water tank abuts the first seal; and the second seal is adapted to be in sealing relationship with the surface surrounding the air outlet of the water tank when the humidifier lid is in the closed position.

8. A respiratory treatment device comprising a flow generator and a humidifier adapted to receive a supply of air at positive pressure from the flow generator and deliver it to an air delivery tube;
the humidifier includes a base, a humidifier lid having an outlet and being movable between closed and open positions while connected to the base, and a water tank, and the water tank includes a water tank lid including an outlet;

the water tank is removably and sealably receivable in the base to form an air flow path for air received from the flow generator to an interior of the water tank;
the humidifier lid is connectable to the air delivery tube, and includes a seal to sealingly contact around the outlet of the water tank lid such that the humidifier includes a sealed air flow path extending from the interior of the water tank and through the outlet of the humidifier lid.

9. The respiratory treatment device of claim 8 constructed and arranged to allow removal of the water tank without detaching the air delivery tube from the humidifier lid.

10. The device of claim 8 or 9 wherein the water tank further comprises a rear first aperture constructed and arranged to align with an opening in the base of the humidifier when the water tank is located in the base to receive the supply of air at positive pressure from the flow generator therethrough.

11. The device of claim 10 wherein the water tank includes a flat surface surrounding the rear opening.

12. The device of claim 11 wherein the humidifier base includes a seal adapted to abut the flat surface of the water tank in a locus surrounding the rear opening to create a sealed air path from the flow generator to the water tank.

13. The device of any one of claims 8 to 12 wherein the humidifier lid is constructed and arranged to seal against the water tank lid to form an air path between the interior of the tank and the air delivery tube when the humidifier lid is in the closed position.

14. The device of any one of claims 8 to 13 wherein the seal comprises a removably attachable gasket.

15. The device of claim 14 wherein the seal comprises a curved sealing flange.

16. The device of claim 12 wherein the outlet of the water tank lid includes an aperture and a surface adjacent or surrounding said aperture.

17. The device of claim 16 wherein the curved sealing flange is adapted to seal against the surface of the water tank lid when the humidifier lid is in the closed position.

18. The device of any one of claims 8 to 17 wherein the humidifier lid comprises an outlet pipe arranged at an acute angle to the humidifier lid.

19. The device of any one of claims 8 to 18 wherein the humidifier lid is pivotally mounted to the base.

20. The device of claim 19 wherein the humidifier lid is rotatable through a first angle to establish a travel range, and upon rotation beyond the travel range, the humidifier lid is adapted to flexurly release from the base.

21. The device of any one of claims 8 to 20 wherein the water tank lid includes an arcuate air flow path for air received from the flow generator.

22. The device of claim 21 wherein the arcuate air flow path is U-shaped.

23. The device of any one of claims 8 to 22 wherein the humidifier lid further comprises a locking mechanism.

24. The device of claim 23 wherein the locking mechanism is configured to retain the humidifier lid in sealing relationship with the water tank lid when the locking mechanism is engaged.

25. The device of claim 24 wherein the humidifier is removably attachable to the flow generator.

26. The device of claim 25 further comprising a latch to retain the humidifier to the flow generator.

27. The device of claim 13, wherein the water tank and the base include surfaces that are engagable with one another to press the water tank and the water tank lid rearwards relative to the base when the humidifier lid is closed.

28. A humidifier adapted for interconnection between a continuous positive airway pressure device and an air delivery tube for delivery of a supply of humidified breathable gas to a patient for treatment of obstructive sleep apnea, and to establish an air flow path between the continuous positive airway pressure device and the air delivery tube, the humidifier having a water tank and the humidifier being constructed and arranged to allow removal of the water tank for refilling with water without disconnection of the air delivery tube, the water tank having a water tank lid including an outlet, wherein the water tank is configured to be in sealing relationship with the air flow path when an inlet to the water tank abuts a first seal of the humidifier and a lid of the humidifier sealingly contacts a surface surrounding the outlet of the water tank.

29. The humidifier of claim 28 wherein the lid of the humidifier further comprises a second seal located on an underside of the lid.

30. The humidifier of any one of claims 28 or 29 wherein the lid of the humidifier is structured to rotate about a hinge between an open position and a closed position.

31. The humidifier of claim 30 wherein the water tank is configured to be in sealing relationship with the second seal when the lid of the humidifier is in the closed position.

32. A method of sealably locating a removable humidifier water tank in a humidifier base comprising:

positioning a rear surface of the humidifier water tank to abut a humidifier seal supported by the humidifier base to form a sealed air path from a flow generator outlet into an interior of the water tank; and pressing a lid of the humidifier onto a lid of the water tank to sealingly contact a surface surrounding an outlet aperture of the water tank lid to form a sealed air path between an interior of the humidifier water tank and an air delivery tube.

33. The method of claim 32 further comprising rotating the lid of the humidifier from an open position to a closed position.

34. The method of claim 32 or 33 further comprising rotating the lid of the humidifier about a hinged connection.

35. The method of any one of claims 32 to 34 further comprising closing the lid of the humidifier using a pivoting movement.

36. The method of any one of claims 32 to 35 further comprising engaging a humidifier lid locking mechanism.

37. The method of any one of claims 32 to 36 whereby the positioning comprises positioning the humidifier water tank so that a humidifier seal abuts a rear opening of the humidifier water tank in a locus surrounding the rear opening of the humidifier water tank.

38. The method of any one of claims 32 to 37 further comprising pressing or moving the humidifier water tank rearwards.

39. In a humidifier having a tank and a humidifier lid, a method of filling the tank with water comprising:

leaving an air delivery tube connected to the humidifier lid;
releasing a locking mechanism of the humidifier lid;

rotating the humidifier lid from a closed position to an open position to release a sealed connection between the humidifier lid and an outlet of a lid of the tank;
subsequent to rotating the humidifier lid, removing the tank from a humidifier base; and filling the tank with water.

40. A humidifier for delivering humidified breathable gas to a patient, including:
a humidifier case having a hinged humidifier lid, a removable water tank adapted to be positioned at least partly in said case, the water tank having a tank lid, a heater in heat transfer communication with said water tank, a gas flow path including a gas inlet, a humidified gas outlet and an intermediate gas flow path to contact the gas with water vapour from said water tank, wherein said water tank has a gas passage inlet and a gas passage outlet communicating with said gas flow path, said gas passage outlet being formed in the tank lid, said humidifier further including a gas passage inlet seal to form a first sealing connection between said gas passage inlet and said gas flow path, and a gas passage outlet seal to form a second sealing connection between the gas passage outlet and said gas flow path, wherein said first and second sealing connections are established by inserting said water tank at least partly within the base and hinged closing of said humidifier lid to sealingly contact a surface surrounding the gas passage outlet of the tank lid.

41. A humidifier according to claim 40, wherein said gas passage inlet is located on a rear face of said water tank and aligns with a gas passage aperture on an opposed face of said case.

42. A humidifier according to claim 41, wherein closing of said humidifier lid pushes said water tank rearwards to establish sealing between the gas passage inlet of the water tank and said gas passage aperture of said case.

43. A humidifier according to claim 42, wherein said gas passage inlet seal is attached to said gas passage aperture and wherein closing said humidifier lid pushes the water tank onto said gas passage inlet seal causing sealing contact between said gas passage inlet seal and said rear face in a locus surrounding said gas passage inlet.

44. In a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a removable water tank having an inlet and a water tank lid including an outlet, a base having a blower outlet and a water-tank-receiving-portion, and a hinged lid with an engagable locking mechanism, a method of forming a first seal between the water tank inlet and the blower outlet of the base and forming a second seal between the outlet of the water tank lid and the hinged lid, the method comprising:

(i) placing the water tank at least partly in the tank-receiving-portion of the base so as to position the water tank inlet and the blower outlet adjacent one another;
(ii) closing the hinged lid to establish sealing contact between the hinged lid and a surface surrounding the outlet of the water tank lid; and (iii) engaging the locking mechanism.

45. The method of claim 44 wherein the blower outlet includes front-facing seal forming surface, and wherein the placing includes placing the water tank inlet and the front-facing seal forming surface adjacent one another.

46. The method of claim 45 whereby placing the water tank in the water-tank-receiving portion of the base further includes placing the water tank against the seal forming surface of the blower outlet.

47. The method of any one of claims 44 to 46, wherein the hinged lid further comprises a generally cylindrical portion, and the method further comprises connecting with an air delivery conduit tube to the generally cylindrical portion so that the supply of breathable gas can be provided to a patient interface.

48. In a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a removable water tank including a tank lid having an air outlet, the humidifier assembly including a hinged lid with an engagable locking mechanism, a method of forming a seal between a surface surrounding the air outlet formed on the tank lid and the air delivery portion comprising:
(i) closing the hinged lid to establish a sealed connection between the hinged lid and the surface surrounding the air outlet of the tank lid; and (ii) engaging the locking mechanism.

49. The method of claim 48 wherein the hinged lid has an underside, and the underside includes a seal forming surface, and wherein the method includes establishing the sealed connection between the seal forming surface and the surface surrounding the air outlet of the tank lid when the hinged lid is closed.

50. The method of claim 49 wherein the seal forming surface comprises a removably attachable gasket, and the method further comprises establishing the sealed connection between the gasket and the surface surrounding the air outlet of the tank lid when the hinged lid is closed.

51. The method of claim 50 wherein the removably attachable gasket is formed of silicone.

52. A humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tank having a water tank lid, a removable water tank air inlet and a water tank air outlet, the water tank air outlet being formed in the water tank lid, a humidifier base having a blower outlet and a water-tank-receiving portion, and a humidifier lid having an air delivery portion adapted to mate with an air delivery tube so that the supply of breathable gas can be provided to a patient interface, wherein said water-tank-receiving portion and water tank have complementary formations adapted to guide positioning of said water tank to align said water tank air inlet with said blower outlet, the humidifier lid being adapted to sealingly contact a surface surrounding the water tank air outlet of the water tank lid upon closing of the humidifier lid, to establish a sealed air flow path extending through the water tank lid and the humidifier lid.

53. A humidifier according to claim 52 wherein said complementary formations further guide positioning of said water tank to align said air outlet with a position of said air delivery portion of said humidifier lid when said humidifier lid is closed.

54. A humidifier for delivering humidified breathable gas to a patient, including a humidifier case having a humidifier lid, a removable water tank at least partially within said case and including a water tank lid, said humidifier lid being adapted to seal around an outlet aperture of the water tank lid when the humidifier lid is closed, a heater in heat transfer communication with said water tank, a gas flow path including a gas inlet, a humidified gas outlet in said humidifier lid and an intermediate gas flow path which contacts the gas with water vapour from said water tank, and a gas outlet seal operatively associated with said humidifier lid whereby closing said humidifier lid creates sealed communication between said humidified gas outlet and a gas space of said water tank.

55. A humidifier according to claim 54 wherein said gas outlet seal contacts said water tank lid in a locus surrounding an outlet of said gas space.

56. A humidifier according to claim 54 or 55 wherein said humidifier lid is hinged to said case.

57. A humidifier according to any one of claims 54 to 56 wherein said water tank includes a channel in an upper surface of said water tank.

58. The humidifier of claim 3, wherein the humidifier lid remains connected with the base when the tank is removed.

59. The humidifier of claim 4, wherein the humidifier lid is adapted to be pivotally rotated to the open position to allow removal and/or insertion of the water tank from the water tank receiving portion of the humidifier base.

60. The method of claim 39 further comprising removing the lid of the tank before filling the tank with water.

61. A respiratory apparatus for treating a patient comprising a base and a tank, a flow path extending from an inlet of the base to an outlet of the base, the tank forming an intermediate part of the flow path and including a tank inlet and a tank lid having a tank outlet, the base having a rear tank seal, a top tank seal, and a humidifier lid having an inner surface on which the top tank seal is mounted, the humidifier lid being movable between an open position in which the tank is removably insertable into the base and a closed position, wherein the tank and the base are configured and arranged such that insertion of the tank in the base and closing of the humidifier lid seals the tank inlet and outlet against the rear tank seal and the top tank seal, respectively, and secures the tank relative to the base.

62. The respiratory apparatus according to claim 61, wherein the humidifier lid is pivotable relative to the base.

63. The respiratory apparatus according to claim 61 or 62, further comprising a locking structure to lock the humidifier lid in its closed position.

64. The respiratory apparatus according to claim 63, wherein the locking structure is configured to provide an audible "click".

65. The respiratory apparatus according to any one of claims 61 to 64, wherein the rear tank seal and the top tank seal are configured to allow sealing engagement between the tank and the base without insertion or connection of a tube or connector of the tank and base relative to one another.

66. An apparatus for treatment of obstructive sleep apnea, comprising:
a continuous positive airway pressure device capable of providing a supply of air at a pressure in the range of about 4cmH2O to about 20cmH2O; and a humidifier connectable to the continuous positive airway pressure device, the humidifier including:
a humidifier base, a humidifier lid hingedly connected to the humidifier base to allow the humidifier lid to close and open, the humidifier lid including an air delivery pipe constructed and arranged to mate with an air delivery tube, the humidifier lid further including a lid seal, the humidifier base further including a humidifier heater plate and a humidifier base seal; and a removable water tank having a tank base to receive water and a tank lid, the tank base including a heat conductive portion to conduct heat from the humidifier heater plate to water in the tank in use, the apparatus further comprising a latch to releasably connect the continuous positive airway pressure device to the humidifier; and a locking mechanism constructed and arranged to releasably hold the humidifier lid when closed, wherein the humidifier base is constructed and arranged to receive the water tank when the humidifier lid is open;
wherein, when the humidifier base receives the water tank, the heat conductive portion of the water tank is positioned relative to the humidifier heater plate to allow heat transfer communication therebetween in use;
wherein, when the continuous positive airway pressure device and the humidifier are latched together and the humidifier lid is closed with the water tank placed in the humidifier base, a sealed gas flow path is established, said sealed gas flow path extending from the continuous positive airway pressure device, through a humidifier base seal located between the humidifier base and a rear surface of the water tank, through an interior of the water tank, through the lid seal surrounding an outlet of the tank lid and located on an underside of the humidifier lid, and to the air delivery pipe of the humidifier lid; and wherein an engagement face of the continuous positive airway pressure device includes electrical connectors to deliver power to the humidifier heater plate.

67. The apparatus of claim 66, further comprising a backflow prevention structure located adjacent a mouth of the inlet aperture.

68. The apparatus of claim 67, wherein the backflow prevention structure comprises a non-return valve.

69. The apparatus of any one of claims 66 to 68, wherein the humidifier includes a pair of flanges for engagement with mating recesses on the continuous positive airway pressure device.

70. The apparatus of any one of claims 66 to 69, wherein the continuous positive airway pressure device is constructed and arranged to detect automatically the presence of the humidifier and adjust an automatic control algorithm of the continuous positive airway pressure device when the continuous positive airway pressure device and the humidifier are connected.

71. The apparatus of any one of claims 66 to 70, further wherein the water tank includes filling level graduations scribed or otherwise marked on the wall of the water tank.

72. The apparatus of any one of claims 66 to 71, wherein the humidifier base and the water tank have complementary configurations to guide positioning of the water tank in the humidifier base.

73. A compact apparatus for the treatment of obstructive sleep apnea, comprising:
a continuous positive airway pressure device; an air delivery tube; and a humidifier including:
a humidifier base, a humidifier lid, a humidifier tank and a humidifier tank lid, and a humidifier heater plate;

wherein the continuous positive airway pressure device and the humidifier are releasably connectable by a latch;
wherein the humidifier lid includes an air delivery portion adapted to mate with the air delivery tube; wherein the humidifier lid and the humidifier base are connected by a hinge adapted to allow the humidifier lid to rotate between a closed position and an open position;
wherein the humidifier lid includes a locking mechanism adapted to releasably hold the humidifier lid in the closed position;
wherein the humidifier base is adapted to receive the humidifier tank when the humidifier lid is in an open position and to locate the humidifier tank in heat transfer communication with the humidifier heater plate, wherein a gas flow path extends from the continuous positive airway pressure device, through the humidifier tank to and the air delivery tube when the humidifier lid is in the closed position;
wherein the humidifier base includes a first gas flow path extending between the continuous positive airway pressure device and an interior of the humidifier tank, and the humidifier base includes a second gas flow path extending between the interior of the humidifier tank and the air delivery tube;
wherein the humidifier base includes a tank receiving portion and the humidifier tank and the tank receiving portion have complementary configurations to guide positioning of the humidifier tank in the tank receiving portion and to align the sealing of the gas flow passage between the base and the humidifier tank;
wherein the first gas flow path includes an air inlet on the humidifier tank that is adapted to introduce gas flow into the humidifier tank;
wherein the humidifier tank may be removed or refilled without the need to remove the air delivery tube, and wherein the humidifier tank can be positioned in a sealing position on the humidifier base without requiring interconnection of a tube;
wherein the humidifier base and the humidifier lid are capable of one-handed engagement and disengagement to open and close the humidifier lid;
wherein the humidifier tank is structured for one-handed insertion at least partly into the humidifier base and one-handed removal from the humidifier base;

wherein the humidifier tank further comprises a rearwardly facing air inlet aperture constructed and arranged to align with an aperture of the humidifier when the humidifier tank is located at least partly in the tank receiving portion to receive the supply of gas at positive pressure from the continuous positive airway pressure device;
wherein the humidifier lid has an underside that includes a seal forming surface comprising a removable attached gasket to seal the gas flow passage between the humidifier tank and the air delivery tube, and the humidifier tank lid has an outlet opening that is configured to communicate with the attached gasket whereby a sealing connection is easily created when the humidifier lid is closed;
wherein the removable attached gasket comprises a curved sealing flange;
wherein the humidifier base has an aperture adapted to receive a supply of breathable gas from the continuous positive airway pressure device and rear tank seal extending about the aperture;
wherein the humidifier tank has an air inlet and an air outlet, and respective surfaces surrounding the air inlet and air outlet;
wherein the humidifier lid has the air delivery portion adapted to mate with the air delivery tube so that the supply of breathable gas can be provided to a patient interface;
wherein the rear tank seal is adapted to be in sealing relationship with the surface surrounding the air inlet of the humidifier tank when the humidifier tank abuts the seal, and the removable attached gasket is adapted to be in sealing relationship with the surface surrounding the air outlet of the humidifier tank lid when the humidifier lid is in a closed position,

74. The apparatus of claim 73 wherein the apparatus is capable of generating from 4-20cmH2O pressure and a gas flow rate of 120L/min.

75. The apparatus of claim 73 or 74 wherein the continuous positive airway pressure device has a total volume of about 2 liters or less.

76. The apparatus of claim 73 wherein the apparatus is capable of generating from 4-20cmH2O pressure, and wherein a flow generator unit within the continuous positive airway pressure device has a total volume of about 2 liters or less.

77. The apparatus of claim 76 wherein the apparatus is capable of delivering therapy with a total radiated noise of less than 33 dbA when operating at 10 cmH2O.

78. The apparatus of any one of claims 73 to 77 wherein there is integration between the continuous positive airway pressure device and the humidifier upon physical engagement of the continuous positive airway pressure device and the humidifier with respect to gas flow.

79. The apparatus of any one of the claims 73 to 78 wherein there is integration between the continuous positive airway pressure device and the humidifier upon physical engagement of the continuous positive airway pressure device and the humidifier with respect to gas flow and electrical interconnectivity.

80. The apparatus of any one of the claims 73 to 79 wherein there is integration between the continuous positive airway pressure device and the humidifier upon physical engagement of the continuous positive airway pressure device and the humidifier with respect to gas flow, electrical interconnectivity, and data connection once the apparatus is powered up.

81. The apparatus of claim 80 wherein there is automatic data connection between the continuous positive airway pressure device and the humidifier upon physical engagement of the continuous positive airway pressure device and the humidifier without the need for any other process interconnection once the apparatus is powered up.

82. The apparatus of any one of the claims 73 to 81 wherein the humidifier is adapted to press the humidifier tank rearwards when the humidifier lid is closed.

83. The apparatus of any one of the claims 73 to 82 wherein upon physical engagement the apparatus is configured to guard against flowback of water from the humidifier tank to the continuous positive airway pressure device.

84. The apparatus of any one of the claims 73 to 83 wherein upon physical engagement between the continuous positive airway pressure device and the humidifier the apparatus is configured to guard against flowback of water from the humidifier tank to the continuous positive airway pressure device while at the same time improving the uptake of water vapor in the humidifier, wherein the air inlet of the tank is positioned to at least partially protect against flowback of water from the air inlet to the continuous positive airway pressure device, when the humidifier is tipped.

85. The apparatus of claim 83 wherein the humidifier includes a non-return valve to guard against flowback of water from the humidifier tank to the continuous positive airway pressure device.

86. The apparatus of any one of the claims 73 to 85 wherein upon physical engagement between the continuous positive airway pressure device and the humidifier the apparatus is configured to guard against the ingress of moisture to the power supply due to flowback of moisture from the humidifier.

87. The apparatus of any one of the claims 73 to 86 wherein the humidifier heater plate has a heating surface and the humidifier tank has a heat transfer surface and these surfaces are shaped to correspond to each other so as to maintain close heat transfer communication.

88. The apparatus of any one of the claims 73 to 87 wherein the latch to releasably connect the continuous positive airway pressure device and the humidifier is configured such that when the two are brought together by linear movement towards each other a latch activated tongue structure located on the humidifier engages a slot mechanical structure located on the continuous positive airway pressure device and snaps together the humidifier and the continuous positive airway pressure device so that the two are mechanically and lockably engaged.

89. A respiratory apparatus for treating a patient, comprising:
a flow generator including:

a fan to generate a supply of pressurized breathable gas in the range of 4-20 cm H2O, the fan including a motor and an impeller, the fan being provided within a fan housing having a cover and a base, the flow generator further including an engagement face and at least one electrical connector and an air connector that protrude from the engagement face, a display and at least one key or device to set one or more parameters of the flow generator, an external case having top and bottom cases of rigid plastics material, a chassis including a cavity within the external case to house the fan, the cavity including a base, side walls extending upwards from the base, and a lid to enclose the fan, a printed circuit board provided in a space between the chassis and an interior surface of the top case, the printed circuit board having the display mounted thereon, the external case having a rear wall including an air inlet that is in communication with an air inlet passage formed in the chassis, the inlet of the external case being provided with a filter, the fan housing including integral feet extending into recesses within an elastomer damping member;
and a humidifier including:
a base unit designed for attachment to the flow generator, the base unit having a heater plate and an air inlet port configured to receive the air connector of the flow generator, a water tank placable in and removable from the base unit, the water tank including a tank lid including an air outlet aperture, the water tank including a heat conductive portion to conduct heat from the heater plate to heat water in the water tank in use, the water tank having an air inlet aperture leading to a passage within the water tank, a face of the base unit includes a guide that seats in a corresponding recess in the engagement face of the flow generator when the flow generator and the humidifier are brought together by linear movement towards each other, a latch including a latch retainer movable substantially vertically and resiliently urged substantially downwardly by a spring, so that a substantially downwardly extending finger of a tongue engages in a slot in the flow generator and snaps home to releasably engage the flow generator and the humidifier, an electrical connector to mate with the electrical connector of the flow generator, an elastomer airway seal provided to the base unit, to communicate the inlet port of the base unit to the air inlet aperture of the water tank, a humidifier lid hingedly attached to the base unit and movable between open and closed positions, wherein as the humidifier lid is moved to the closed position, the water tank is translated rearwards within the base unit so that a front facing surface of the airway seal abuts a generally flat rear surface of the water tank surrounding the inlet aperture of the tank, the humidifier lid including an exit aperture and an elastomer seal on an inside surface of an upper or top wall of the lid, the elastomer seal having, in the closed position of the lid, a downwardly facing surface to sealingly contact a surface of the water tank lid that surrounds the outlet aperture of the water tank lid, the humidifier lid including an outlet pipe extending through the exit aperture and the elastomer seal and having a bent portion extending at an acute angle from an exterior surface of the upper or top wall, and a catch provided to the humidifier lid to maintain the lid in the closed position, with the water tank being held securely relative to the base unit.

90. The respiratory apparatus according to claim 89, further comprising a control to adjust the degree of humidification of the humidifier.

91. The respiratory apparatus according to claim 89 or 90, further comprising at least one muffler provided within the chassis.

92. The respiratory apparatus according to any one of the claims 89 to 91, wherein the flow generator has a volume of 2 liters or less.

93. The respiratory apparatus according to any one of the claims 89 to 92, wherein the fan is structured to generate a flow rate of 120 liters/minute.

94. The method of claim 32, further comprising moving the lid of the humidifier between an open position and a closed position, whereby the sealed air path is established when the lid of the humidifier is in the closed position.

95. A humidifier comprising:
a latch adapted to releasably engage with a continuous positive airway pressure device;
an air inlet port adapted for sealable connection to an outlet of the continuous positive airway pressure device and being further adapted to receive a supply of air at positive pressure from said continuous positive airway pressure device;

a heater plate;
a water tank adapted to receive the supply of air at positive pressure and adapted to be in heat transfer communication with the heater plate, said water tank having a water tank lid including an outlet aperture;
a humidifier lid having a humidifier air outlet adapted for connection with an air delivery tube to deliver the supply of air at positive pressure to a mask, the humidifier lid being movable between closed and open positions to allow selective coupling and decoupling of the humidifier air outlet and the water tank lid via the outlet aperture; and wherein said humidifier is constructed and arranged to retain the water tank in place when the humidifier lid is closed and to allow removal of the water tank when the humidifier lid is open.

96. The humidifier according to claim 95, further comprising an electrical connector to mate with an electrical connector of the continuous positive airway pressure device, wherein the latch, the air inlet port and the electrical connector are provided along a common engagement face of the humidifier that is structured to engage with an engagement face of the continuous positive airway pressure device.

97. The humidifier according to claim 95 or 96, wherein removal of the water tank does not require removal of the air delivery tube.

98. The humidifier according to claim 97, wherein the air delivery tube is connected to the lid in the open and closed positions in use.

99. The humidifier according to any one of claims 95 to 98, further comprising a base to receive the water tank, the outlet remaining with the base when the tank is removed.

100. A humidifier comprising a removable water tank having a water tank lid;
a humidifier base having a water tank receiving portion; and a humidifier lid having an outlet adapted to mate with an air delivery conduit;

wherein the humidifier lid is adapted to be in sealing relationship with an outlet of the water tank lid to allow a flow of air from the water tank to the air delivery conduit when the humidifier lid is in a closed position.

101. The humidifier according to claim 100, wherein the humidifier lid is adapted to be pivotably rotated to an open position to allow removal and insertion of the water tank relative to the water tank receiving portion of the humidifier base.

102. The humidifier according to claim 100 or 101, wherein the water tank includes a tank base, and the tank lid is removably attached to the tank base.

103. The humidifier according to claim 102, wherein the tank base and the tank lid are arranged for pivotable movement relative to one another.

104. The humidifier according to any one of claims 100 to 103, wherein the humidifier lid is a hinged lid.

105. The humidifier according to any one of claims 100 to 104, wherein the humidifier lid is connected to the humidifier base by hinges.

106. A breathable gas supply apparatus for treatment of respiratory disorders comprising:
a continuous positive airway pressure device; and a humidifier adapted for releasable connection to the continuous positive airway pressure device, the humidifier comprising:
a humidifier base having 1) an air inlet port adapted to receive a supply of breathable gas from the continuous positive airway pressure device and 2) an aperture downstream of the air inlet port;
a first seal adjacent the aperture;
a removable water tank having an air inlet and an air outlet, and a respective surface surrounding each of the air inlet and the air outlet, the surface surrounding the air inlet being flat;

a humidifier lid with an air delivery portion adapted to mate with an air delivery tube so that the supply of breathable gas can be provided to a patient interface; and a second seal located on an underside of the humidifier lid, wherein:
the first seal is adapted to be in sealing relationship with the flat surface surrounding the air inlet of the water tank when the water tank abuts the first seal; and the second seal is adapted to be in sealing relationship with the surface surrounding the air outlet of the water tank when the humidifier lid is in a closed position.

107. The breathable gas supply apparatus according to claim 106, wherein the first seal includes a relatively flat surface that seals with the flat surface surrounding the air inlet of the water tank, and the second seal includes a surface that seals with the surface surrounding the air outlet of the water tank.

108. The breathable gas supply apparatus according to claim 107, wherein the second seal includes an inwardly oriented sealing flange that seals with the surface of the air outlet of the water tank.

109. The breathable gas supply apparatus according to claim 108, wherein the sealing flange is provided to a distal end of the second seal, and the sealing flange includes an exterior end surface that abuts the surface of the air outlet.

110. The breathable gas supply apparatus according to claim 109, wherein the second seal includes an aperture through which pressurized gas flows in use, the aperture defining a longitudinal axis generally parallel to the flow of pressurized gas through the aperture in use, the second seal and the outlet of the water tank abutting one another to form a seal in a sealing plane that is generally perpendicular to the longitudinal axis.

111. The breathable gas supply apparatus according to claim 110, wherein the sealing plane is substantially co-planar or coincident with the surface of the outlet of the water tank.

112. The breathable gas supply apparatus according to claim 111, wherein the second seal is positioned on an underside of the humidifier lid.

113. The breathable gas supply apparatus according to claim 112, wherein the humidifier lid includes an outlet pipe configured for connection to an air delivery tube.

114. The breathable gas supply apparatus according to claim 113, wherein the first seal extends about the aperture.

115. A humidifier adapted to receive a supply of air at positive pressure for delivery to a patient circuit having an air delivery tube and a mask for treating a patient with positive pressure ventilation therapy, the humidifier comprising:

a humidifier base defining an air inlet port connectable with an outlet port of a therapy device, a heater plate, and a latch to allow connection with the therapy device, a removable water tank configured to hold water for humidification, the water tank being removable from the humidifier base, the water tank having a tank base, a tank lid and a seal therebetween, the water tank having a tank inlet located on the back of the water tank and an outlet hole on the tank lid, and a humidifier door in sealed contact with the outlet hole of the water tank via a door seal positioned between the humidifier door and the water tank lid, the humidifier door having a pair of hinges rotatably connected to the humidifier base and having an air outlet port configured for connection to the air delivery tube and for delivering moisturized air to the mask, the door being rotatable between an open position and a closed position, the door having a release to release the door from the closed position.

116. The humidifier according to claim 115, wherein the humidifier base includes a guide that seats in a corresponding recess in the therapy device when the therapy device and the humidifier are brought together by linear movement towards each other.

117. The humidifier according to claim 115 or 116, further comprising one or more filling level graduations scribed or otherwise marked on the water tank to indicate correct filling height.

118. The humidifier according to claim 117, wherein the door is rotatable from the closed position to a maximum extent of normal travel in the open position, and wherein, upon further rotation of the door beyond the maximum extent, the door becomes removed from the base.

119. The humidifier according to any one of claims 115 to 118, wherein the tank base includes a tank pan.

120. The humidifier according to claim 119, wherein said tank inlet is structured and positioned relative to the water tank to at least partially protect against flowback of water from the water tank to the therapy device via the tank inlet.

121. The humidifier according to claim 120, further including a one-way valve near a mouth of the tank inlet of the water tank.

122. The humidifier according to claim 121, wherein the air outlet port is angled at an acute angle from an upper wall of the humidifier lid.

123. The humidifier according to claim 122, wherein the tank lid and the tank base are configured for pivotal connection at the back of the water tank.

124. The humidifier according to any one of claims 115 to 123, further comprising a locking mechanism to lock the door in position and configured to provide an audible "click"
sound upon locking.

125. The humidifier according to claim 124, wherein the locking mechanism is provided to cause the audible "click" in the closed position.

126. Apparatus for treatment of a respiratory disease comprising:
a therapy device to generate pressurized gas; and the humidifier according to any one of claims 115 to 125.

127. A humidifier adapted to receive a supply of air at positive pressure for delivery to an air delivery tube, comprising a base with a heater plate, a removable water tank configured to be at least partly received in the base, and a humidifier lid in sealed communication with an outlet of the water tank and having an air delivery tube connector configured for connection to the air delivery tube, wherein the water tank includes a tank base and a water tank lid.

128. The humidifier according to claim 127, wherein the water tank lid is configured for pivoting movement relative to the tank base.

129. The humidifier according to claim 127 or 128, wherein the humidifier lid is hingedly connected to the base.

130. The humidifier according to any one of claims 127 to 129, wherein the water tank further includes a tank air flow path extending from an inlet of the water tank to an outlet of the water tank, wherein the base includes a base air flow path extending (i) from an air inlet port of the base to a first seal, positioned between the inlet of the water tank and an aperture of the base downstream from the air inlet port, and (ii) from a second seal between the outlet of the water tank to the air delivery tube connector, and wherein the tank air flow path and water tank are positioned between the first and second seals.

131. The humidifier according to claim 130, wherein the inlet of the water tank is positioned on a rear wall of the water tank.

132. The humidifier according to claim 131, wherein the outlet of the water tank is positioned on an upper or top wall of the water tank.

133. The humidifier according to claim 132, wherein the first and second seal portions are pressure-assisted seals.

134. The humidifier according to claim any one of claims 130 to 133, wherein the air delivery tube connector comprises an angled air outlet pipe.

135. The humidifier according to claim 134, wherein the air outlet pipe extends through the humidifier lid, defining a rim.

136. The humidifier according to claim 135, wherein the second seal fits over the rim.

137. The humidifier according to claim 136, wherein the first seal includes a connector portion and a peripheral seal to abut and seal against a flat surface radially surrounding an aperture of the inlet of the water tank.

138. The humidifier according to claim 137, wherein the second seal includes a sealing flange to abut and sealingly engage a surface radially surrounding an aperture of the outlet of the water tank.

139. A humidifier adapted for interconnection between a continuous positive airway pressure device and an air delivery tube for delivery of a supply of humidified breathable gas to a patient for treatment of obstructive sleep apnea, said humidifier including an air flow path between the continuous positive airway pressure device and the air delivery tube, the humidifier having a water tank and the humidifier being constructed and arranged to allow removal of the water tank for refilling with water without disconnection of the air delivery tube, wherein the water tank is configured to be in sealing relationship with the air flow path when an inlet to the water tank is pressed against a first seal of the humidifier and a lid of the humidifier is pressed against an outlet of the water tank.

140. The humidifier according to claim 139, wherein the lid of the humidifier further comprises a second seal located on an underside of the lid.

141. The humidifier according to claim 140, wherein the lid of the humidifier is structured to pivot about a hinge between an open position and a closed position.

142. The humidifier according to claim 141, wherein the water tank is configured to be in sealing relationship with the second seal when the lid of the humidifier is in a closed position.

143. A respiratory apparatus for a patient, comprising:
a base unit having a hinged lid and a base seal, the lid having an aperture, an inside lid seal provided around the aperture, and an air delivery tube connector extending from an outside surface of the lid and configured to be connected to an air delivery tube; and a removable humidifier tank having a generally flat rear inlet sealing surface engaged with a generally flat sealing surface of the base seal when the lid is open and the tank is received in the base unit, the tank including a top outlet surface engaged with a surface of the lid seal and in communication with the connector via the aperture when the lid is closed, wherein the tank is sealingly positioned in the base unit without requiring tubular connection between the tank and base unit.

144. The respiratory apparatus according to claim 143, wherein the lid seal includes an aperture bounded by a side wall and a curved sealing flange extending from the side wall and towards the aperture, said curved sealing flange being adapted to seal against the top surface of the tank lid.

145. The respiratory apparatus according to claim 144, wherein the sealing flange seals in a plane that is perpendicular to an axis of the outlet of the tank lid.

146. The respiratory apparatus according to any one of claims 143 to 145, wherein the sealing plane is coincident with the top surface of the tank.

147. The respiratory apparatus according to claim 146, wherein the base and lid seals are configured as pressure-assisted seals.

148. The respiratory apparatus according to claim 147, wherein as pressurized gas is introduced into the gas flow path in use, this pressurized gas assists the sealing flange of the lid seal or a peripheral seal of the base seal, in creating or supplementing a firm seal around the respective inlet and outlet of the tank.

149. The respiratory apparatus according to claim 148, wherein the tank is structured to be secured relative to the base unit when the lid is closed, and the tank is structured to be removable for refilling by rotating the lid open without removing the air delivery tube.

150. The respiratory apparatus according to claim 149, wherein the lid is configured for disconnection from the base unit when the lid is pivoted beyond a maximum extent of normal travel.

151. A respiratory apparatus for a patient, comprising:
a base unit having a hinged lid, said base unit further including a first seal portion and a second seal portion; and a removable humidifier tank having a generally flat inlet sealing surface engaged with a generally flat sealing surface of the first seal portion when the lid is open and the tank is received in the base unit, the tank including an outlet surface engaged with a surface of the second seal portion when the lid is closed, wherein in use the first and second seal portions seal with the inlet and outlet of the tank in sealing planes that are generally perpendicular to a direction of flow of pressurized gas through the inlet and the outlet such that the tank is sealingly positioned in the base unit without requiring tubular interconnection between the tank and base unit.

152. The respiratory apparatus according to claim 151, wherein the second seal includes an aperture bounded by a side wall and a curved sealing flange extending from the side wall and towards the aperture, said curved sealing flange being adapted to seal against the outlet.

153. The respiratory apparatus according to claim 152, wherein each sealing plane is coincident with the flat surface surrounding the inlet and outlet, respectively.

154. The respiratory apparatus according to claim 153, wherein the first and second seals are configured as pressure-assisted seals.

155. The respiratory apparatus according to claim 154, wherein as pressurized gas is introduced into the gas flow path in use, the pressurized gas assists the first and second seals in creating or supplementing a firm seal around the respective inlet and outlet of the tank.

156. The respiratory apparatus according to claim 155, wherein the tank is secured relative to the base unit when the lid is closed, and the tank is removed for refilling by rotating the lid open without removing the air delivery tube from the humidifier.

157. A humidifier for a continuous positive airway pressure device, the humidifier comprising:
a removable water tank having a water tank lid, said water tank lid having a water tank outlet, a humidifier base having a water tank receiving portion to receive the water tank and a heater plate to heat water in the water tank;
a humidifier lid having a humidifier lid outlet adapted to mate with an air delivery tube;
and a lid seal positioned between the water tank lid and the humidifier lid, said lid seal being positioned and structured to form a seal surrounding the water tank outlet of the tank lid to establish a sealed air flow path extending from the water tank outlet of the water tank lid, and through the humidifier lid outlet, wherein the water tank includes an air inlet aperture structured and located to at least partly protect against flowback of water from the inlet aperture of the water tank to the continuous positive airway pressure device in use, at least when the humidifier is tipped.

158. The humidifier of claim 157, further comprising backflow prevention structure located adjacent a mouth of the inlet aperture, to at least partly protect against flowback of water from the water tank to the continuous positive airway pressure device in use.

159. The humidifier of claim 158, wherein the backflow prevention structure comprises a non-return valve.

160. The humidifier of any one of claims 157 to 159, wherein the water tank lid is configured to be detachable from the water tank.

161. The humidifier of claim 160, further comprising a seal positioned between the water tank and the water tank lid.

162. The humidifier of claim 161, wherein the water tank and the water tank lid are configured for one-handed disengagement by squeezing at least a portion of the tank lid.

163. The humidifier of claim 162, further comprising a connection positioned at a rear end of the water tank, wherein said water tank lid is pivotable about the connection when removing the tank lid from the tank, such that the tank lid separates from the tank at the front end.

164. The breathable gas supply apparatus of claim 106, further comprising a control circuit for the humidifier, including a user operable control to select a desired gas humidity setting and a heater control circuit to determine a target heater temperature corresponding to the humidity setting and to control a heater to attain said temperature, wherein said user operable control includes an off setting for which said heater control circuit is adapted to select a target heater temperature less than a lowest operating temperature of said humidifier.

165. The breathable gas supply apparatus of claim 106, further comprising a blower enclosure for said continuous positive airway pressure device, the blower enclosure including a metal container overmoulded with an acoustically damping polymer lining.

166. The breathable gas supply apparatus of claim 106, wherein the continuous positive airway pressure device includes a top case having an air inlet and a replaceable filter and a filter cover fitted to the top case.

167. The breathable gas supply apparatus of claim 166, further comprising a bottom case comprising a shell of a rigid plastics material overmoulded with an elastomer.

168. The breathable gas supply apparatus of claim 106, further comprising a printed circuit board including an LCD and a support for the LCD.

169. The respiratory apparatus according to claim 89, further comprising a handle assembly including a pair of attachment arms, each attachment arm having a projection received in a respective track of said case, and a handle retention member that attaches to said case to retain said handle projections against travel along said track.

170. The respiratory apparatus according to claim 169, wherein said handle retention member comprises a cover plate comprising a part of an exterior of said case.

171. The respiratory apparatus according to claim 170, wherein said handle retention member has retaining projections extending into said tracks to limit travel of said handle projections along said tracks.

172. The respiratory apparatus according to claim 171, wherein said handle retention member retains said handle projections adjacent a closed end of said tracks.

173. The apparatus of claim 73, further comprising a fan mounted within a fan housing, wherein the fan housing comprises a cover and a rigid plastic base, wherein a bottom surface of the rigid plastic base is provided with radial stiffening ribs, and further wherein an elastomer damping member is overmoulded to the rigid plastic base to cover a bottom surface of the rigid plastic base between the radial stiffening ribs, and further wherein a plurality of feet are moulded integrally with the rigid plastic base, and further wherein said feet are constructed and arranged to extend proud of the elastomer damping member and to receive respective helical mounting springs for mounting the fan on a base of a fan cavity.

174. In a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tub having an inlet, a base having a blower outlet and a water-tub-receiving-portion, and a hinged lid with an engagable locking mechanism, a method of forming a seal between the water tub inlet and the blower outlet of the base comprising the steps of : (i) placing the water tub in the tub-receiving-portion of the base so as to position the inlet and the outlet adjacent one another; (ii) closing the hinged lid; and (iii) engaging the locking mechanism.

175. The method of claim 174 wherein the blower outlet includes a front-facing seal forming surface.

176. The method of claim 175 whereby the step of placing the water tub in the water-tub-receiving portion of the base further includes the step of placing the water tub against the seal forming surface of the blower outlet.

177. The method of claim 176 wherein the hinged lid further comprises a generally cylindrical portion adapted to mate with an air delivery conduit so that the supply of breathable gas can be provided to a patient interface.

178. A method of sealably locating a humidifier water tub in a humidifier base comprising:

positioning a rear surface of the humidifier water tub to abut a humidifier seal to form an air path from a flow generator outlet into an interior of the water tub; and pressing a humidifier lid of the humidifier to engage a surface of a tub lid of the humidifier water tub to form a sealed air path between an interior of the humidifier water tub and an air delivery conduit connector positioned on the humidifier lid.

179. The method according to claim 178, further comprising pivoting the humidifier lid of the humidifier from an open position to a closed position.

180. The method according to claim 178 or 179, further comprising pivoting the humidifier lid of the humidifier about a hinged connection.

181. The method according to any one of claims 178 to 180, further comprising closing the humidifier lid of the humidifier using a pivoting movement.

182. The method according to any one of claims 178 to 181, further comprising engaging a humidifier lid locking mechanism to retain the tub.

183. The method according to any one of claims 178 to 181, whereby positioning the rear surface of the humidifier water tub to abut a humidifier seal comprises positioning the humidifier water tub so that the humidifier seal abuts a substantially flat surface surrounding a rear inlet of the humidifier water tub.

184. The method according to any one of claims 178 to 182, wherein the pressing of the humidifier lid results in rearward movement of the tub.

185. A humidifier adapted for interconnection between a continuous positive airway pressure device and an air delivery tube for delivery of a supply of humidified breathable gas to a patient for treatment of obstructive sleep apnea, and to define an air flow path between the continuous positive airway pressure device and the air delivery tube, the humidifier having a water tank and the humidifier being constructed and arranged to allow removal of the water tank for refilling with water without disconnection of the air delivery tube, wherein the water tank is configured to be in sealing relationship with the air flow path when an inlet to the water tank abuts a first seal of the humidifier and a lid of the humidifier is pressed against an outlet of the water tank.

186. The humidifier according to claim 185, wherein the lid of the humidifier further comprises a second seal located on an underside of the lid.

187. The humidifier according to claim 186, wherein the lid of the humidifier is structured to pivot about a hinge between an open position and a closed position.

188. The humidifier according to claim 187, wherein the water tank is configured to be in sealing relationship with the second seal when the lid of the humidifier is in the closed position.

189. A breathable gas supply apparatus for treatment of respiratory disorders comprising:
a continuous positive airway pressure device; and a humidifier adapted for releasable connection to the continuous positive airway pressure device, the humidifier comprising:
a humidifier base having an air inlet port adapted to receive a supply of breathable gas from the continuous positive airway pressure device, said humidifier base further having a tub receiving surface including a heater plate;
a water tub having an air inlet and an air outlet, and a flat inlet surface surrounding the air inlet and an outlet surface surrounding the air outlet, the water tub having a bottom portion provided with a heat conducting surface;
a pivotable humidifier lid movable between an open position in which the water tub may be placed on the tub receiving surface of the humidifier base, and a closed position in which the tub is secured to the humidifier base and the heat conducting surface of the water tub is placed in alignment with the heater plate of the humidifier base;
a first seal adjacent the air inlet of the water tub; and a second seal adjacent the air outlet of the water tub, wherein the first seal is adapted to be in sealing relationship with the flat inlet surface surrounding the air inlet of the water tub when the water tub abuts the first seal, and wherein the second seal is adapted to be in sealing relationship with the outlet surface surrounding the air outlet of the water tub when the water tub abuts the second seal.

190. The breathable gas supply apparatus according to claim 189, wherein the first seal includes a relatively flat surface that seals with the flat inlet surface surrounding the air inlet of the water tub, and the second seal includes a relatively flat surface that seals with the outlet surface surrounding the air outlet of the water tub, the outlet surface being flat.

191. The breathable gas supply apparatus according to claim 189 or 190, wherein the second seal includes an inwardly oriented sealing flange that seals with the outlet surface surrounding the air outlet of the water tub.

192. The breathable gas supply apparatus according to claim 191, wherein the sealing flange is provided to a distal end of the second seal, and the sealing flange includes an exterior end surface that abuts the outlet surface surrounding the air outlet.

193. The breathable gas supply apparatus according to any one of claims 189 to 192, wherein the second seal includes an aperture through which pressurized gas flows in use, the aperture defining a longitudinal axis parallel to the flow of pressurized gas through the aperture in use, the second seal and the outlet surface of the water tank abutting one another to form a seal in a sealing plane that is perpendicular to the longitudinal axis.

194. The breathable gas supply apparatus according to claim 193, wherein the sealing plane is coincident with the outlet surface of the air outlet of the water tub.

195. The breathable gas supply apparatus according to any one of claims 189 to 194, wherein the second seal is positioned on an underside of the humidifier lid.

196. The breathable gas supply apparatus according to any one of claims 189 to 195, wherein the first seal includes a connector portion and a peripheral seal to abut and seal against the flat inlet surface surrounding the air inlet of the water tub.

197. The breathable gas supply apparatus according to any one of claims 189 to 196, wherein the humidifier lid includes an outlet pipe configured for connection to an air delivery tube.

198. The breathable gas supply apparatus according to any one of claims 189 to 197, wherein the first seal includes an aperture through which pressurized gas flows in use, the aperture defining a longitudinal axis parallel to the flow of pressurized gas through the aperture in use, the first seal and the flat inlet surface of the water tank abutting one another to form a seal in a sealing plane that is perpendicular to the longitudinal axis.

199. The breathable gas supply apparatus according to claim 198, wherein the sealing plane is coincident with the flat inlet surface of the air inlet of the water tub.

200. In a humidifier assembly for a flow generator used in delivery of a supply of breathable gas to a patient for treatment of sleep disordered breathing, the humidifier assembly comprising a water tub having an inlet, a base having an aperture adapted to communicate with output from the flow generator and a water-tub-receiving-portion, and a hinged lid with an engagable locking mechanism, a method of forming a seal between the water tub inlet and the aperture of the base comprising the steps of : (i) placing the water tub in the tub-receiving-portion of the base so as to position the inlet and the outlet adjacent one another; (ii) closing the hinged lid to establish the seal with the water tub inlet; and (iii) engaging the locking mechanism.

201. The method of claim 200 wherein the aperture includes a front-facing seal forming surface.

202. The method of claim 201 whereby the step of placing the water tub in the water-tub-receiving portion of the base further includes the step of placing the water tub against the seal forming surface of the aperture.

203. The method of any one of claims 200 to 202 wherein the hinged lid further comprises a generally cylindrical portion adapted to mate with an air delivery conduit so that the supply of breathable gas can be provided to a patient interface.

204. A breathable gas supply apparatus for treatment of respiratory disorders comprising:
a continuous positive airway pressure device; and a humidifier adapted for releasable connection to the continuous positive airway pressure device, the humidifier comprising:
a humidifier base having an air inlet port adapted to receive a supply of breathable gas from the continuous positive airway pressure device, said humidifier base further having a tub receiving surface including a heater plate;
a water tub having an air inlet and an air outlet, and a respective sealing surface surrounding each of the air inlet and the air outlet, each sealing surface being provided on an exterior surface of a wall of the water tub, each said sealing surface being positioned radially outward relative to an aperture defining the air inlet and air outlet, respectively, the water tub having a bottom portion provided with a heat conducting surface;
a pivotable humidifier lid movable between an open position in which the water tub may be placed on the tub receiving surface of the humidifier base, and a closed position in which the tub is secured to the humidifier base and the heat conducting surface of the water tub is placed in alignment with the heater plate of the humidifier base;
a first seal adjacent the air inlet of the water tub; and a second seal adjacent the air outlet of the water tub, wherein the first seal is adapted to be in sealing relationship with the sealing surface surrounding the air inlet aperture of the water tub when the water tub abuts the first seal, and wherein the second seal is adapted to be in sealing relationship with the sealing surface surrounding the air outlet aperture of the water tub when the water tub abuts the second seal.

205. The breathable gas supply apparatus according to claim 204, wherein the first seal includes a relatively flat surface that seals with the sealing surface surrounding the air inlet of the water tub, and the second seal includes a relatively flat surface that seals with the sealing surface surrounding the air outlet of the water tub.

206. The breathable gas supply apparatus according to claim 204 or 205, wherein the second seal includes an inwardly oriented sealing flange that seals with the sealing surface surrounding the air outlet of the water tub.

207. The breathable gas supply apparatus according to claim 206, wherein the sealing flange is provided to a distal end of the second seal, and the sealing flange includes an exterior end surface that abuts the sealing surface surrounding the air outlet.

208. The breathable gas supply apparatus according to any one of claims 204 to 207, wherein the second seal includes an aperture through which pressurized gas flows in use, the aperture defining a longitudinal axis parallel to the flow of pressurized gas through the aperture in use, the second seal and the sealing surface of the air outlet of the water tank abutting one another to form a seal in a sealing plane that is perpendicular to the longitudinal axis.

209. The breathable gas supply apparatus according to claim 208, wherein the sealing plane is coincident with the sealing surface of the air outlet of the water tub.

210. The breathable gas supply apparatus according to any one of claims 204 to 209, wherein the second seal is positioned on an underside of the humidifier lid.

211. The breathable gas supply apparatus according to any one of claims 204 to 210, wherein the first seal includes a connector portion and a peripheral seal to abut and seal against the sealing surface surrounding the air inlet of the water tub.

212. The breathable gas supply apparatus according to any one of claims 204 to 211, wherein the humidifier lid includes an outlet pipe configured for connection to an air delivery tube.

213. The breathable gas supply apparatus according to any one of claims 204 to 212, wherein each said sealing surface is flat.

214. The breathable gas supply apparatus according to any one of claims 204 to 213, wherein each said aperture defines a rim, and the sealing surface surrounding each said aperture is positioned radially outwards from the rim.

215. The breathable gas supply apparatus according to any one of claims 204 to 214, wherein the wall of the water tub having the air inlet includes an interior surface opposite the exterior surface, and a connecting portion defining a rim and connecting the exterior and interior surfaces, said sealing surface associated with the air inlet being positioned radially outwards of the rim on the exterior surface of the wall, and wherein the wall of the water tub having the air outlet includes an interior surface opposite the exterior surface, and a connecting portion defining a rim and connecting the exterior and interior surfaces, said sealing surface associated with the air outlet being positioned radially outwards of the rim on the exterior surface of the wall.

216. A respiratory treatment device comprising a flow generator and a humidifier adapted to receive a supply of air at positive pressure from the flow generator and deliver it to an air delivery tube, wherein:
the humidifier includes a base, a humidifier lid, and a water tank, and the water tank includes a water tank lid;
the water tank is removably receivable in the base to define a first air flow path from the flow generator to an interior of the water tank; and the humidifier lid is connectable to the air delivery tube, and is adapted to form a seal with the water tank lid to define a second air flow path from the interior of the water tank to the air delivery tube.

217. The respiratory treatment device according to claim 216 constructed and arranged to allow removal of the water tank without detaching the air delivery conduit from the humidifier lid.

218. The device according to claim 216 or 217, wherein the water tank further comprises a rear first aperture constructed and arranged to align with an opening in the humidifier when the water tank is located in the base to receive the supply of air at positive pressure from the flow generator therethrough.

219. The device according to claim 218, wherein the water tank includes a first flat surface surrounding the rear first aperture.

220. The device according to claim 219, wherein the humidifier base includes a seal adapted to abut the first flat surface of the water tank in a locus surrounding the rear first aperture to seal the first air path from the flow generator to the water tank.

221. The device according to any one of claims 216 to 220, wherein the humidifier lid is movable relative to the water tank to seal against the water tank lid to form the second air path when the humidifier lid is in a closed position.

222. The device according to any one of claims 216 to 221, adapted to press the water tank rearwards when the humidifier lid is closed.

223. The device according to any one of claims 216 to 222, wherein the humidifier lid further comprises a humidifier lid seal.

224. The device according to claim 223, wherein the humidifier lid seal comprises a removably attachable gasket.

225. The device according to claim 223, wherein the humidifier lid seal comprises a curved sealing flange.

226. The device according to claim 223, wherein the water tank lid comprises a second aperture and the seal of the humidifier lid is constructed and arranged to sealingly surround the second aperture when the humidifier lid is in a closed position.

227. The device according to claim 223, wherein the water tank lid comprises an air outlet second aperture and a second flat surface adjacent said air outlet second aperture.

228. The device according to any one of claims 216 to 227, wherein the humidifier comprises an outlet pipe arranged at an acute angle to the lid.

229. The device according to any one of claims 216 to 228, wherein the humidifier lid is pivotally mounted to the base.

230. The device according to claim 229, wherein the lid is pivotable through a first angle to define a normal travel range, and upon pivoting beyond the normal travel range, the lid being adapted to flexurly release from the base.

231. The device according to any one of claims 216 to 230, wherein the water tank lid is structured to define an arcuate air flow path for air received from the flow generator.

232. The device according to claim 231, wherein the arcuate air path is constructed to cause the air within the container to swirl and thus enhance the uptake of water vapour from the water contained in the tank.

233. The device according to claim 231, wherein the arcuate air flow path is U-shaped.

234. The device according to any one of claims 216 to 233, wherein the humidifier lid further comprises a locking mechanism.

235. The device according to claim 234, wherein the locking mechanism is configured to retain the humidifier lid in sealing relationship with the water tank lid when the locking mechanism is engaged.

236. The device according to any one of claims 216 to 235, wherein the humidifier is removably attachable to the flow generator.

237. The device according to claim 236, further comprising a latch to retain the humidifier to the flow generator.

238. The device according to any one of claims 216 to 237, wherein the humidifier lid is structured and configured to press the water tank lid rearwards as the humidifier lid is closed.

239. An apparatus for treatment of obstructive sleep apnea, comprising:
a continuous positive airway pressure device; and a humidifier including:
a humidifier base, a humidifier lid hingedly connected to the humidifier base to allow the humidifier lid to close and open, the humidifier lid including an air delivery pipe constructed and arranged to mate with an air delivery tube, the humidifier base further including a humidifier heater plate; and a water tank having a tank base to receive water and a tank lid, the tank base including a heat conductive portion to conduct heat from the humidifier heater plate to water in the tank in use, the apparatus further comprising a latch to releasably connect the continuous positive airway pressure device to the humidifier; and a locking mechanism constructed and arranged to releasably hold the humidifier lid when closed, wherein the humidifier base is constructed and arranged to receive the water tank when the humidifier lid is open, wherein, when the humidifier base receives the water tank, the heat conductive portion of the water tank is positioned relative to the humidifier heater plate to allow heat transfer communication therebetween in use, and wherein, when the continuous positive airway pressure device and the humidifier are latched together and the humidifier lid is closed with the water tank placed in the humidifier base, a sealed gas flow path is defined, said sealed gas flow path extending from the continuous positive airway pressure device, through the water tank and to the air delivery pipe of the humidifier lid.

240. The apparatus according to claim 239, wherein the humidifier base defines a first gas flow path between the continuous positive airway pressure device and the water tank, and a second gas flow path between the water tank and the air delivery tube, such that the water tank forms an intermediate gas flow path positioned between the first and second gas flow paths of the humidifier base.

241. The apparatus according to claim 240, further comprising a first seal positioned at an inlet of the water tank and a second seal positioned at an outlet of the water tank.

242. The apparatus according to claim 241, wherein the second seal is mounted on an underside of the humidifier lid.

243. The apparatus according to claim 240, wherein an inlet of the water tank is positioned on a rear wall of the water tank.

244. The apparatus according to claim 240, wherein an outlet of the water tank is positioned on an upper wall of the water tank.

245. The apparatus according to claim 241, wherein the first and second seals are pressure-assisted seals.

246. The apparatus according to claim 242, wherein the air delivery pipe extends through the humidifier lid, defining a rim.

247. The apparatus according to claim 246, wherein the second seal fits over the rim.

248. The apparatus according to any one of claims 239 to 247, further comprising the air delivery tube, said air delivery tube being connectable at a first end thereof to the air delivery pipe of the humidifier lid, said air delivery tube being connectable at a second end thereof to a mask worn by a patient in use.

249. A method for easily inserting and removing a CPAP humidifier water tub from a base for a respiratory apparatus for treating a patient with a respiratory disorder, the method comprising:
placing the tub into the base; and closing a movable lid of the base to retain the tub in place and to seal an inlet and an outlet of the tub relative to the base, thus establishing a sealed air flow path extending from an inlet of the base to an outlet of the base, without requiring the patient to establish tubular interconnection between the base and the tub.

250. The method according to claim 249, further comprising:
opening the lid;
removing the tub from the base;
filling the tub with water; and placing the tub back on the base and closing the lid.

251. The method according to claim 250, wherein filling the tub with water does not require removal of an air delivery tube from the respiratory apparatus, and does not require separation of a lid of the tub from a base of the tub.

252. The method according to claim 251, further comprising providing an inlet seal adjacent the tub inlet and air outlet seal adjacent the tub outlet.

253. The method according to any one of claims 249 to 252, wherein the lid is pivotable.

254. The method according to any one of claims 249 to 253, further comprising using pressurized gas to assist in establishing a seal between the tub and the base.

255. The method according to any one of claims 249 to 253, wherein the seal between the tub and base is established by abutting a respective surface surrounding the inlet and outlet of the tub with a respective seal mounted on the base.

256. An apparatus for treatment of obstructive sleep apnea, comprising:
a continuous positive airway pressure device capable of providing a supply of air at a pressure in the range of about 4cmH2O to about 20cmH2O; and a humidifier connectable to the continuous positive airway pressure device, the humidifier including:
a humidifier base, a humidifier lid hingedly connected to the humidifier base to allow the humidifier lid to close and open, the humidifier lid including an air delivery pipe constructed and arranged to mate with an air delivery tube, the humidifier lid further including a lid seal, the humidifier base further including a humidifier heater plate and a humidifier base seal;
and a water tank having a tank base to receive water and a tank lid, the tank base including a heat conductive portion to conduct heat from the humidifier heater plate to water in the tank in use, the apparatus further comprising a latch to releasably connect the continuous positive airway pressure device to the humidifier; and a locking mechanism constructed and arranged to releasably hold the humidifier lid when closed, wherein the humidifier base is constructed and arranged to receive the water tank when the humidifier lid is open;
wherein, when the humidifier base receives the water tank, the heat conductive portion of the water tank is positioned relative to the humidifier heater plate to allow heat transfer communication therebetween in use;
wherein, when the continuous positive airway pressure device and the humidifier are latched together and the humidifier lid is closed with the water tank placed in the humidifier base, a sealed gas flow path is established, said sealed gas flow path extending from the continuous positive airway pressure device, through the humidifier base seal located between the humidifier base and a rear surface of the water tank, through an interior of the water tank, through the lid seal surrounding an outlet of the tank lid and located on an underside of the humidifier lid, and to the air delivery pipe of the humidifier lid; and wherein an engagement face of the continuous positive airway pressure device includes electrical connectors to deliver power to the humidifier heater plate.

257. The apparatus of claim 256, further comprising a backflow prevention structure located adjacent a mouth of the inlet aperture.

258. The apparatus of claim 257, wherein the backflow prevention structure comprises a non-return valve.

259. The apparatus of any one of claims 256 to 258, wherein the humidifier includes a pair of flat male blade connectors for engagement with mating connectors on the continuous positive airway pressure device.

260. The apparatus of any one of claims 256 to 259, wherein the continuous positive airway pressure device is constructed and arranged to detect automatically the presence of the humidifier and adjust an automatic control algorithm of the continuous positive airway pressure device when the continuous positive airway pressure device and the humidifier are connected.

261. The apparatus of any one of claims 256 to 260, further wherein the water tank includes filling level graduations scribed or otherwise marked on the wall of the water tank.

262. The apparatus of any one of claims 256 to 261, wherein the humidifier base and the water tank have complementary configurations to guide positioning of the water tank in the humidifier base.

263. The apparatus of claim 262 wherein the water tank further comprises a water tank seal.

264. The apparatus of any one of claims 256 to 263 wherein the water tank is constructed and arranged to allow disengagement of the water tank base and the water tank lid.

265. The apparatus of any one of claims 256 to 264 further comprising an air delivery conduit and a patient interface, and wherein the air delivery conduit is connected to the air delivery pipe of the humidifier lid, and the air delivery conduit is connected to the patient interface for delivery of humidified air to a patient.

266. The apparatus of any one of claims 256 to 265, wherein the humidifier lid is constructed and arranged so that it is rotatable from a closed position to a maximum extent of normal travel in an open position, and wherein, upon further rotation of the humidifier lid beyond the maximum extent, the humidifier lid becomes removed from the base.

267. The apparatus of any one of claims 256 to 266, wherein the locking mechanism is configured to provide an audible "click" sound upon locking.

268. The apparatus of any one of claims 256 to 267, wherein the lid seal is a pressure-assisted seal.

269. The apparatus of any one of claims 256 to 268, wherein the humidifier base seal is a pressure-assisted seal.

270. The apparatus of claim 269, wherein the humidifier base seal includes a connector portion and a peripheral seal to abut and seal against a flat surface radially surrounding an aperture of an inlet of the water tank.

271. The apparatus of claim 270, wherein the lid seal includes a sealing flange to abut and sealingly engage a surface radially surrounding an aperture of the outlet of the water tank lid.

272. The apparatus of claim 271, further comprising a user operable control for selecting a desired air humidity setting.

273. The apparatus of claim 272, constructed and arranged so that when the water tank is received in the tank base and the humidifier lid is closed, the tank base and the tank lid are pressed rearwards.