WO1999057815A1

WO1999057815A1 - Physiological monitoring of a subject

Info

Publication number: WO1999057815A1
Application number: PCT/IL1999/000229
Authority: WO
Inventors: Lior Goldenberg
Original assignee: Alorman-Advanced Medical Technologies Ltd.
Priority date: 1998-05-03
Filing date: 1999-05-03
Publication date: 1999-11-11
Also published as: IL124294A0; AU3531799A

Abstract

A system (26) for physiological monitoring of a subject (21) including sensors (22, 28) at portions of the subject (21) for sensing body state indications and for providing output signals corresponding to the sensed body state indications, signal conditioning circuits (23, 34) for conditioning the signals, for example, by amplifying and filtering them, an analog to digital A/D interface (24), preferably an audio circuit of the standard sort generally employed for processing audio inputs in a computerized sound system, and a data processor (25) to process and analyze the resulting data. The A/D interface (24) includes input channels (31) with associated analog to digital conversion (32) and output circuits (29), with a resolution of at least 8 bits and with a frequency range of about 10 Hertz to 20 kiloHertz. The system (26) preferably includes a joystick port (33). Also, a method for physiological monitoring of a subject and for signal processing in physiological monitoring of a subject (21) employing the aforementioned system.

Description

PHYSIOLOGICAL MONITORING OF A SUBJECT

FIELD OF THE INVENTION

The present invention relates to systems for physiological monitoring in general and, in particular, for performing signal processing therein.

BACKGROUND OF THE INVENTION

There are many medical and therapeutic situations requiring physiological monitoring of a subject or patient. Often, it is desired to monitor physiological quantities as they vary in time. A well-known example is the electrocardiogram (ECG), a graphical record of the electric potentials produced by activity of the heaπ, which has a cyclical time dependence. Another example is electromyography (EMG), in which the electric potentials produced by activity of regular muscles are measured. In this case, the signals have a more complex time dependence which exhibits characteristic frequencies depending on which muscles are being observed and their state at the time of observation. Current measurement systems and methods require the use of either specially designed circuits, which are generally usable in only a limited number of cases, or the use of frequency analyzers, which are typically expensive.

SUMMARY OF THE INVENTION

The present invention seeks to provide a system and method for physiological monitoring which are simpler and less expensive than those known in the art.

The present invention further seeks to provide a method for signal processing in such monitoring, which overcomes disadvantages of known art, by employing an analog to digital (A/D) interface, preferably an audio circuit of the sort generally employed for processing audio inputs in a computerized sound system.

There is thus provided, in accordance with a preferred embodiment of the invention, a system for physiological monitoring of a subject including sensors at portions of the subject for sensing body state indications and for providing analog output signals corresponding to the sensed body state indications, signal conditioning circuits for conditioning the analog signals, for example, by amplifying and filtering them, an analog to digital (A/D) interface, preferably an audio circuit of the sort generally employed for processing audio inputs in a computerized sound system, and a data processor to process and analyze the resulting data. The A/D interface includes input channels with associated analog to digital conversion and output circuits, with a resolution of at least 8 bits and with a frequency range of about 10 Hertz to 20 kiloHertz. The system also preferably includes a joystick port.

In accordance with a preferred embodiment of the invention, the sensors are electrodes which sense electric potentials produced by muscular activity of the subject. Further in accordance with a preferred embodiment of the invention, the electrodes may be used in groups to monitor the muscular activity of the subject.

Further in accordance with a preferred embodiment of the invention, the system also includes additional sensors to measure additional physiological parameters of the subject, such as temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, or force exerted by the muscle or muscle groups being monitored, which bear upon the measurements performed by the system. The sensors produce signals corresponding to the parameters which are passed to the data processor, for inclusion in .the data processing and analysis, via the communications ports, such as the joystick port, of the system.

2 In accordance with an alternative embodiment of the invention, the system further includes one or more multiplexer circuits, which receive and multiplex signals from a number of sensors or sensor groups and feed them into input channels of the A/D interface and which receive and multiplex signals from additional sensors and feed them into communications ports of the system.

In accordance with yet a further preferred embodiment of the invention, there is provided a method of physiological monitoring of a subject and a method of signal processing in physiological monitoring of a subject employing the system described hereinabove. The method includes the steps of:

sensing body state indications at selected portions of the subject;

providing analog output signals corresponding to the sensed body state indications; digitizing the analog output signals; providing the digitized signals to a data processor; and

processing and analyzing the digitized signals. Further in accordance with a preferred embodiment of the invention, the step of sensing body state indications includes:

sensing electric potentials at selected portions of the subject;

producing analog output signals corresponding thereto; and

conditioning the analog output signals. In further accordance with a preferred embodiment of the invention, the method further includes the steps of:

measuring further preselected physiological body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, or force exerted by muscle; producing output signals corresponding to the measured body state indications; and providing the body state indication signals to communications ports on the system for processing and analysis, together with the digitized signals, by means of the data processor.

Additionally in accordance with a preferred embodiment of the present invention, the step of digitizing is performed via an analog to digital (A/D) interface included in an audio circuit of the sort generally operative to be employed for processing audio inputs for a computerized sound system, which has a joystick-type input port and at least one input channel operable to receive analog signal inputs within a predetermined frequency range and which includes at least one analog to digital converter associated with the at least one input channel operative to convert analog signals to digital signals with a preselected resolution and having a preselected frequency response, and wherein the step of providing the digitized signals includes the substeps of: measuring further preselected body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, and force exerted by muscle; producing output signals corresponding to the measured body state indications; providing the body state indication output signals to the joystick-type input port on the audio circuit; providing additional body state indication output signals to communications ports on the data processor; and

providing the resulting signals, together with the digitized signals to the data processor for processing and analysis therein.

Further in accordance with a preferred embodiment of the invention, the step of sensing electric potentials includes the step of placing a group of sensors at portions of the subject whereat muscular activity of the subject may be sensed. In accordance with an alternative embodiment of the invention, the step of sensing electric potentials further includes the step of placing a multiplicity of sensors or sensor groups on the subject; and the method includes, after the step of conditioning the analog signals, the step of multiplexing the analog signals via a multiplexer circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more easily understood and appreciated from the following detailed description, taken in conjunction with the drawing, in which'

Fig 1 is a block diagram representation of a physiological monitoring system, constructed and operative in accordance with a preferred embodiment of the present invention

DETAILED DESCRIPTION OF THE INVENTION

Referring now to Figure 1, there is seen a schematic illustration of a system, referred to generally as 10, for physiological monitoring of a subject 21, constructed and operative in accordance with a preferred embodiment of the present invention. In a preferred embodiment of the present invention, system 10 is used, inter alia, for electromyographical (EMG) monitoring of the subject 21. There is thus provided a sensor 22 which, in the present embodiment, is exemplified by electrodes positioned on or below, such as needle EMG electrodes, the body surface of the subject 21 for sensing electrical activity of muscles. It should be noted that the scope of the present invention includes electrodes used singly or in groups to sense the activity of a muscle or a group of muscles. It will be appreciated by persons skilled in the art that the signals produced by electrodes 22 will vary as the subject 21 uses the muscles being observed and that this variation will exhibit characteristic frequencies depending on which muscles are being observed and their state at the time of observation. Electrodes 22 produce analog signals which are conditioned by preamplifiers 23, which amplify the signals and filter out noise, such as unwanted frequency components, notably that of the line power, 50 or 60 Hertz, depending on the country.

The conditioned signals produced by preamplifiers 23 are passed to the input channels 31 of an analog to digital (A/D) interface24 forming part of a computer system 26. A/D interface 24 may be an audio circuit of the sort employed for processing audio inputs for a computerized sound system, such as the Sound Blaster AWE64 ™ produced by Creative Labs Ltd., details of which may be found on the internet site URL: http://www.cle.creaf.com/. Alternatively, A/D interface 24 may be a circuit included on the motherboard of computer system 26, or it may be included in a video camera. A/D interface 24 includes circuits 32 for performing analog to digital conversion (A/D) on signals passing via input channels 31, which typically have a frequency response ranging substantially from 10 Hertz to 20 kiloHertz. The analog to digital conversion is preferably performed with a resolution of 16 bits; although a resolution of 8 bits or greater is sufficient for the EMG measurements, being performed in accordance with the present embodiment of the invention. Wherein A/D interface 24 is an audio circuit, it

6 preferably includes a joystick port, referenced 33, the use of which is described hereinbelow. Alternatively, for a system with an A D interface 24 other than an audio circuit, other communication ports 35, such as standard serial or parallel ports, or a joystick port, are preferably included in computer system 26 The digitized signals produced by A/D converter 32 are provided by A/D interface 24 internally via computer bus 29 to central processing unit (CPU) 25 of computer system 26 for processing and analysis.

It will be appreciated by persons skilled in the art that the signal processing performed in the present invention by A/D interface 24 would require, in the PRIOR ART, specially designed circuits, which typically could respond to only a limited portion of the frequency range covered by the present invention

Referring again to Figure 1, there may be provided additional sensors 28, included in a preferred embodiment of the present invention, to measure additional physiological parameters of the subject 21 which bear upon the measurements performed by system 10 These additional physiological parameters may include temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, or force exerted by the muscle or muscle groups being monitored These may further include electromyographical monitoring of electrical activity of additional muscles or muscle groups in the subject. Some sensors, such as electrodes 22 for electromyographical monitoring, require additional circuitry for signal conditioning 34 to produce usable signals. Sensors 28 and 22, with signal conditioning circuitry 34 if needed, produce signals corresponding to the parameters which are passed to CPU 25 of computer system 26, for inclusion in the data processing and analysis, via joystick port 33 of A/D interface 24 and bus 29 and, additionally where needed, by other communication ports 35 of computer system 26. It will be appreciated by persons skilled in the art that the utilization of the joystick port 33 included in system 10 of the present invention is a further simplification and improvement over the PRIOR ART by reducing the number of additional signal channeling circuit modules required for the parameters desired to be observed. In an alternative embodiment of the present invention, a number of electrodes 22 or electrode groups are positioned at locations on subject 21 to sense electrical activity of a number of muscles or muscle groups. Each electrode has an associated preamplifier 23, as described above. The signals produced by preamplifiers 23 are passed as inputs to a multiplexer (not shown) which multiplexes the signals and passes them in sequence to input channels 31 of audio interface 24. In the present embodiment, measurements may be performed on a number of muscles or muscle groups at the same time. In similar fashion, in a further alternative embodiment of the present invention, signals corresponding to additional physiological parameters as described above, may be passed as inputs to a multiplexer (not shown) for sequential input to computer system 26 via joystick port 33 of A/D interface 24 and bus 29 or, where needed, by other communication ports 35 of computer system 26.

The present invention further includes a method of physiological monitoring of a subject and a method of signal processing in physiological monitoring of a subject employing the system described hereinabove. The method includes the following steps wherein numbered components of the system which are referenced can be seen in Figure 1 :

positioning electrodes 22, which sense electrical potentials and which provide output signals corresponding to the sensed electrical potentials, at selected portions of the subject 21;

sensing electric potentials and producing analog signals corresponding thereto by means of electrodes 22;

conditioning the analog signals produced by electrodes 22 via preamplifier circuits 23 which filter and amplify them; digitizing the analog signals produced by preamplifier circuits via an A/D interface 24 of the sort generally included in an audio circuit of the sort operative to be employed for processing audio inputs for a computerized sound system, which has input channels 31 operable to receive analog signal inputs within a frequency range of substantially 10 Hertz to 20 kiloHertz and which includes analog to digital converters

32 associated with input channels 31 operative to convert analog signals to digital signals with a resolution of at least 8 bits;

passing the digitized signals produced by A/D interface 24 to the CPU 25 of a computer system 26; and

processing and analyzing the data therein.

The method of the present preferred embodiment of the invention may optionally include the following additional steps which may occur concurrently with the above steps: measuring further preselected physiological body state indications of the subject 21, which may include temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, or force exerted by muscle;

producing output signals corresponding to the measured body state indications;

providing the further parameter signals to a joystick input port 33 on A/D interface 24 (or, alternatively, to additional communications ports 35 of computer system 26, as described above); and passing the resulting signals, together with the digitized signals to CPU 25 for processing and analysis.

In an alternative preferred embodiment of the method of the present invention, the step of positioning electrodes 22 is positioning a group of electrodes 22 at locations on subject 21 whereat muscular activity of the subject 21 may be sensed. In an alternative embodiment of the method of the present invention, the step of positioning electrodes 22 is positioning a number of electrodes or electrode groups 22 and the method further includes, after the step of conditioning the signals, the step of multiplexing the signals via a multiplexer circuit (not shown) before passing the signals to audio interface 24 for processing.

In a further alternative embodiment of the method of the present invention, the step of providing the further parameter signals includes the substep of multiplexing the signals via a multiplexer circuit (not shown) before passing the signals to a joystick input port 33 on A/D interface 24 (or, alternatively, to additional communications ports 35 of computer system 26, as described above).

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is limited solely by the claims, which follow.

10

Claims

A system for physiological monitoring of a subject, including:

at least one sensing apparatus for sensing body state indications at selected portions of the subject, and for providing output signals corresponding to the sensed body state indications; an analog to digital (A/D) interface for receiving said output signals; and data processing apparatus, associated with said A/D interface so as to receive input signals therefrom, for processing and analyzing digital input signals, wherein said A/D interface includes

at least one input channel suitable for receiving signal inputs within a predetermined frequency range; and

output circuitry operative to transmit to said data processing apparatus digital output signals corresponding to the signal inputs received via said at least one input channel

A system according to claim 1, wherein said sensing apparatus includes:

at least one electrode apparatus for sensing, at selected portions of the subject, electrical potentials produced thereat, and for providing output signals corresponding to the sensed electrical potentials, and

at least one signal conditioning circuit associated with said at least one electrode apparatus which includes filtering and amplification means and is operative to receive, as its input signals, the output signals from an associated one of said at least one electrode apparatus and to produce therefrom output signals suitable for input to said audio interface.

11

3. A system according to claim 1, wherein said A/D interface further includes at least one analog to digital converter associated with said at least one input channel operative to convert analog signals to digital signals with a preselected resolution and having a preselected frequency response.

4 A system according to claim 1, and further including at least one sensor for measuring at least one further preselected body state indication of the subject and for producing output signals corresponding thereto, and wherein said data processing apparatus includes a multiplicity of signal input ports, each operative to receive, as input signals, said output signals produced by each said sensor

5 A system according to claim 1 wherein

said A/D interface is an audio card of the sort generally operative to be employed for processing audio inputs in a computerized sound system and which further includes a multiplicity of signal input ports, each operative to receive, as input signals, said output signals produced by each said sensor, and said output circuitry is further operative to transmit to said data processing apparatus digital output signals corresponding to the signal inputs received via each of said multiplicity of signal input ports

6. A system according to claim 5 wherein said multiplicity of signal input ports are of the sort generally operative to be associated with a joystick type device.

7. A system according to claim 2, wherein each said at least one electrode apparatus is operative to sense electric potentials produced by muscular activity of the subject at selected portions of the subject.

12

8. A system according to claim 3, wherein the resolution of said at least one analog to digital converter is at least 8 bits.

9. A system according to claim 1 wherein said predetermined frequency range of said at least one input channel of said A/D interface is substantially 10 Hertz to 20 kiloHertz.

10. A system according to claim 4 wherein said further preselected body state indications of the subject includes at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, force exerted by muscle, and electric potentials produced by muscular activity of the subject at additional selected portions of the subject.

1 1. A system according to claim 1 wherein said at least one input channel of said A/D interface is a group of input channels and wherein said at least one electrode apparatus is at least one group of electrode apparatuses operative to sense, at selected portions of the subject, electric potentials produced by muscular activity of the subject and wherein said at least one signal conditioning circuit is at least one group of signal conditioning circuits.

12. A system according to claim 1 and further including a multiplexer circuit, and wherein said at least one sensing apparatus is a multiplicity of sensing apparatuses and wherein said multiplexer circuit is operative to receive, as its input signals, the output signals produced by said multiplicity of sensing apparatuses, and is also operative to multiplex the signals, and to produce therefrom output signals suitable for input into said at least one input channel of said A/D interface.

13

13. A system according to claim 1 and further including a multiplexer circuit which is operative to receive, as its input signals, the output signals produced by said at least one sensor for measuring at least one further preselected body state indication of the subject and for producing output signals corresponding thereto, and wherein said multiplexer circuit is also operative to multiplex the signals, and to produce therefrom output signals suitable for input into said signal input ports of said data processing apparatus.

14. A method of physiological monitoring of a subject including the steps of: sensing body state indications at selected portions of the subject;

providing analog output signals corresponding to the sensed body state indications; digitizing the analog output signals;

providing the digitized signals to a data processor; and

processing and analyzing the digitized signals.

15. A method according to claim 14 wherein said step of sensing body state indications includes: sensing electrical potentials at selected portions of the subject;

producing analog output signals corresponding thereto; and

conditioning the analog output signals.

14

16. A method according to claim 14 further including the steps of: measuring further preselected body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, and force exerted by muscle; producing output signals corresponding to the measured body state indications; and providing the body state indication output signals to communications ports on the data processor, for processing and analysis therein together with the digitized signals;

wherein said steps of measuring, producing, and providing the body state indication output signals are performed concurrently with said steps of sensing, providing analog output signals, digitizing, and providing the digitized signals.

17. A method according to claim 14 wherein said step of digitizing is performed via an analog to digital (A/D) interface included in an audio circuit of the sort generally operative to be employed for processing audio inputs for a computerized sound system, which has a joystick-type input port and at least one input channel operable to receive analog signal inputs within a predetermined frequency range and which includes at least one analog to digital converter associated with the at least one input channel operative to convert analog signals to digital signals with a preselected resolution and having a preselected frequency response, and wherein said step of providing the digitized signals includes the substeps of:

measuring further preselected body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation

15 in blood, level of sugar in blood, brain activity, nerve activity, and force exerted by muscle; producing output signals corresponding to the measured body state indications; providing the body state indication output signals to the joystick-type input port on the audio circuit; providing additional body state indication output signals to communications ports on the data processor; and providing the resulting signals, together with the digitized signals to the data processor for processing and analysis therein.

18. A method according to claim 15 wherein said step of sensing electrical potentials further includes the step of placing a group of sensors at portions of the subject whereat muscular activity of the subject may be sensed.

19. A method according to claim 15:

wherein said step of sensing electrical potentials further includes the step of placing a multiplicity of sensors; and which includes, after said step of conditioning the analog output signals, the step of multiplexing the analog signals.

20. A method according to claim 16 which includes, after said step of producing output signals corresponding to the further measured body state indications, the step of multiplexing the signals before the step of providing the signals to communications ports on the data processor.

16

21. A method of signal processing in physiological monitoring of a subject including the steps of: sensing body state indications at selected portions of the subject; providing analog output signals corresponding to the sensed body state indications; digitizing the analog output signals;

providing the digitized signals produced by the audio interface to a data processor; and processing and analyzing the digitized signals.

22. A method according to claim 21 wherein said step of sensing body state indications includes: sensing electrical potentials at selected portions of the subject; producing analog output signals corresponding thereto; and conditioning the analog output signals.

23. A method according to claim 21 further including the steps of:

measuring further preselected body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, and force exerted by muscle; producing output signals corresponding to the measured body state indications; and providing the body state indication output signals to communications ports on the data processor, for processing and analysis therein together with the digitized signals;

17 wherein said steps of measuring, producing, and providing the body state indication output signals are performed concurrently with said steps of sensing, providing analog output signals, digitizing, and providing the digitized signals.

24. A method according to claim 21 wherein said step of digitizing is performed via an analog to digital (A/D) interface included in an audio circuit of the sort generally operative to be employed for processing audio inputs for a computerized sound system, which has a joystick-type input port and at least one input channel operable to receive analog signal inputs within a predetermined frequency range and which includes at least one analog to digital converter associated with the at least one input channel operative to convert analog signals to digital signals with a preselected resolution and having a preselected frequency response, and wherein said step of providing the digitized signals includes the substeps of:

measuring further preselected body state indications of the subject including at least one of temperature, breathing rate, heart rate, level of oxygen saturation in blood, level of sugar in blood, brain activity, nerve activity, and force exerted by muscle; producing output signals corresponding to the measured body state indications;

providing the body state indication output signals to the joystick-type input port on the audio circuit; providing additional body state indication output signals to communications ports on the data processor; and

18

25. A method according to claim 22 wherein said step of sensing electrical potentials further includes the step of placing a group of sensors at portions of the subject whereat muscular activity of the subject may be sensed.

26. A method according to claim 22: wherein said step of sensing electrical potentials further includes the step of placing a multiplicity of sensors; and which includes, after said step of conditioning the analog output signals, the step of multiplexing the analog signals.

27. A method according to claim 23 which includes, after said step of producing output signals corresponding to the measured body state indications, the step of multiplexing the signals before the step of providing the signals to communications ports on the data processor.

19