CA2216884A1

CA2216884A1 - Blood sampling device

Info

Publication number: CA2216884A1
Application number: CA002216884A
Authority: CA
Inventors: Toby King; Anne Miller
Original assignee: Bayer Corp
Current assignee: Bayer Corp
Priority date: 1996-10-25
Filing date: 1997-09-29
Publication date: 1998-04-25
Also published as: JPH10127610A; AU4285197A; EP0838195A1; US5873887A; AU693408B2

Abstract

An automatic blood sampling device is provided with a housing (12, 14, 18, 20), a reciprocable shaft (50) disposed in the housing (12, 14, 18, 20), and a lancet (40) operatively coupled to the shaft (50). The lancet (40) is movable between a retracted position in which the lancet (40) is disposed within the housing (12, 14, 18, 20) and an extended position in which the lancet (40) extends outside of the housing (12, 14, 18, 20). The blood sampling device includes means for retaining the lancet (40) in its retracted position, means (51) for causing the lancet (40) to automatically move from its retracted position to its extended position, and means for generating a reduced internal pressure within an area in the housing (12, 14, 18, 20) as the lancet (40) moves from its retracted position to its extended position to facilitate drawing blood from a skin puncture to be made by the lancet (40) into an interior portion of the housing (12, 14, 18, 20), the internal pressure being less than the ambient pressure outside of the housing (12, 14, 18, 20) of the sampling device.

Description

BLOOD S~JMPLING DEVICE

Background o~ the Invention The present invention relates to a blood sampling device that incorporates a lancet ~or piercing the skin and creates a partial vacuum to enhance recovery o~ a sample of blood.
Various types of blood sampling devices ~or drawing a blood sample ~rom a skin puncture made by a lancet have been described.
For example, U.S. Patent No. 5,368,047 to Suzuki, et al. discloses a blood sampling device that has a lancet connected to a spring-loaded plunger that is reciprocable in a cylindrical housing between a retracted position and an extended position. The plunger has a gasket which makes sealing contact with the interior wall o~ the housing when the plunger is moved ~rom its extended position to its retracted position.
In the operation o~ the Suzuki, et al. device, the plunger is pushed to its retracted position by the user and then placed against the skin ~rom which the blood sample is to be drawn Upon being released, the plunger is urged to travel ~rom its retracted position to its extended position via a spring. When the plunger reaches its ~ully extended position, the lancet punctures the skin. A~ter the skin is punctured, the plunger moves back to its retracted position, during which movement the pressure inside the housing is reduced due to the sliding engagement o~ the gasket against the interior wall o~
the housing. This reduced pressure, which is in contact with the skin puncture, enhances passage o~ blood ~rom the puncture into the blood sampling device.

~ummary o~ the Invention The invention is directed to an automatic blood sampling device that is relatively painless and simple to use. The blood sampling device has a housing, a reciprocable sha~t disposed in the housing, and a lancet operatively coupled to the sha~t. The lancet is movable between a retracted position in which the lancet is disposed within the housing and an extended position in which the lancet extends outside o~ the housing.
The blood sampling device includes means ~or retaining the lancet in its retracted position, means ~or causing the lancet to automatically move ~rom its retracted position to its extended position, and means ~or generating a reduced internal pressure within the housing as the lancet moves ~rom its retracted position to its extended position to facilitate drawing blood ~rom a skin puncture to be made by the lancet. The reduced internal pressure in the housing o~ the sampling device is less than the ambient pressure outside the sampling device.
The means ~or generating the reduced internal pressure within the housing may comprise a bore having a substantially air-tight end and a plunger connected to the sha~t. The plunger has an exterior portion which makes sealing contact with the bore so that the reduced internal pressure is ~ormed within the bore when the plunger is moved in a direction away ~rom the air-tight end o~ the bore.
The means ~or retaining the lancet in its retracted position may be a latch mechanism, and the means ~or causing the lancet to automatically move ~rom its retracted position to its extended position may be a spring.
The blood sampling device may also include means ~or venting the reduced internal pressure area within the sampling device to the outside atmosphere, means ~or decelerating the lancet as the lancet moves towards its extended position, and/or a check valve in ~luid communication with the acceleration chamber to allow air to pass from the acceleration chamber to a point outside the housing of the sampling device.
These and other features and advantages of the present invention will be apparent to those of ordinary skill in the art in vlew of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below.
B~ief Description of the Drawings Fig. 1 is a cross-sectional view of one embodiment of a blood sampling device in accordance with the invention;
Fig. 2 is a cross-sectional view of a portion of the blood sampling device shown in a ready position;
Fig. 3 is a top view of a latch mechanism of the blood sampling device;
Fig. 4 is a side view of a latch mechanism of the blood sampling device;
Fig. 5 is a side view of a venting assembly of the blood sampling device; and Fig. 6 is a side view of an alternative embodiment of a venting assembly.

Detailed Desc~iptio~ of the Preferred Embodiments Fig. 1 is a cross-sectional view of a first embodiment of a blood sampling device 10 for taking a sample of blood from a patient. Re~erring to Fig. 1, the blood sampling device 10 has a housing composed of a main body 12, an upper housing portion 14 connected to the main body 12 via a screw 16, a lower housing portion in the form of a sleeve 18 threadably connected to the main body 12, and an end cap 20 threadably connected to the sleeve 18.
An O-ring 22 is disposed between the end cap 20 and the sleeve 18 to provide an air-tight seal between those two components 18, 20, and an O-ring 24 is disposed between the sleeve 18 and the main body 12 to provide an air-tight seal between those two components 12, 18. A
conventional one-way check valve 26 is disposed in a bore formed in the sleeve 18 to allow air to escape from the interior of the blood sampling device 10 to the outside and to prevent air from passing into the interior o~ the sampling device 10.
The blood sampling device 10 has an actuator mechanism composed o~ a semi-spherical knob 30 attached to an actuator 32 via a screw 34. The actuator 32 may be provided with a relatively narrow, outwardly extending key portion 33 which is disposed within a slot (not shown) in an upper surface 35 of the housing portion 14 to prevent rotation of the actuator 32 relative to the housing portion 14. The knob 30 and the actuator 32 are biased downwardly via a helical spring 36 disposed between the upper surface 35 of the housing portion 14 and an annular flange 38 that extends outwardly from the bottom of the actuator 32.
A lancet assembly composed of a lancet 40 and a lancet shaft 42 is disposed in the interior portion of the blood sampling device 10.
The lancet shaft 42 is connected to a cylindrical lancet holder 44, and the lancet holder 44 is connected to a plunger assembly composed of an annular rubber plunger 46 connected to a plunger hub 48. The plunger hub 48 is connected to an elongate shaft 50, and a helical spring 51 is disposed between the plunger hub 48 and an upper internal surface of the main body 12.
The shaft 50 has a latch 52 connected to it via a nut 54 at a fixed position near the upper end of the shaft 50. The latch 52 is adapted to selectively spread apart and engage a plurality of upwardly extending retaining arms 60 of a retainer member 62. Fig.
3 is a top view of the latch 52 and the retaining arms 60, and Fig.

4 is an enlarged side view o~ the latch 52 and portions o~ the retaining arms 60. Re~erring to Figs. 3 and 4, the latch 52 has a pair o~ angled spreading sur~aces 56 and is adapted to selectively engage a pair of outwardly extending ~langes 59 (Fig. 3) integrally ~ormed with the actuator 32. A ledge 64 is ~ormed on each o~
interior sides of the retaining arms 60. Each ledge 64 has a horizontally disposed retaining sur~ace 66 and a diagonally sloped spreading sur~ace 68.
When in the position shown in Fig. 1, the latch 52 rests on top o~ a thin annular washer which is disposed on top o~ a helically coiled spring 70. The spring 70 is supported by a sealing assembly composed o~ a steel washer 71 (Fig. 5) and a sealing member 72. The sealing assembly and the retaining member 62 are connected to the main body 12 via a bolt assembly 74.
Re~erring to Figs. 1 and 5, a venting peg 80 is connected to the actuator 32. The venting peg 80 has a middle cylindrical portion 82 having a relatively small diameter and a bottom portion 84 having a relatively large diameter. The venting peg 80 is movable through a bore ~ormed in the bottom o~ the retainer 62, an aligned bore ~ormed in the steel washer 71 (Fig. 5), and an aligned bore (Fig. 5) ~ormed in the sealing member 72.
When the actuator 32 is ~orced downwardly, the bottom portion 84 o~ the venting peg 80 passes into a cylindrical well 86 ~ormed in the main body 12 so that the relatively thln portlon 82 o~ the ventlng peg 80 is disposed within the aligned bores ~ormed in the members 71, 72. Thus, an air passageway may be selectively ~ormed ~rom a lower internal chamber 88 re~erred to as a suction chamber to an upper internal chamber 90. The chamber 90 is in fluid communication with the outside due to an annular space ~ormed between the actuator 32 and the sur~ace 35 o~ the upper housing portion 14. Air may flow through the air passageway between the chambers 88, 90 as indicated by the arrow in Fig. 5.
A cylindrical internal chamber 92 re~erred to as an acceleration chamber is ~ormed coaxially with the suction chamber 88. The diameter o~ the acceleration chamber 92 is slightly larger than that o~ the suction chamber 88. The rubber plunger 46 has an annular portion 94 having a slightly enlarged diameter. The diameter o~ the annular portion 94 is slightly greater than the internal diameter o~ a portion 88a o~ the suction chamber 88 and less than the internal diameter o~ the acceleration chamber 92.
Consequently, when the rubber plunger 46 is moving within the suction chamber portion 88a, substantially no air passes through the air-tight seal ~ormed by the abutment o~ the annular portion 94 with the internal sur~ace o~ the suction chamber portion 88a. The suction chamber 88 is provided with an upper portion 88b which is slightly reduced in diameter to minimize the dead volume o~ the suction chamber 88.
To use the sampling device 10 to draw a blood sample, the user ~irst pulls the knob 30 upwardly ~rom its position shown in Fig. 1.
As the knob 30 and the actuator 32 to which it is attached move upwardly, the top surfaces o~ the ~langes 59 on the actuator 32 make contact with the bottom sur~ace o~ the latch 52. As the knob 30 continues its upward movement, the ~langes 59 ~orce the latch 52 upwardly, which causes the sha~t 50, the plunger 46, the lancet holder 44 and the lancet sha~t 42 to move upwardly as well As the knob 30 and the latch 52 continue moving upwardly, the angled spreading sur~aces 56 on the latch 52 abut the angled spreading sur~aces 68 on the ledges 64 o~ the retaining members 60 and ~orce the retaining members 60 apart. When the latch 52 is moved upwardly past the ledges 64, the resilient retaining members 60 snap inwardly so that downward movement o~ the latch 52 is prevented due to the ledges 64. Fig. 2 illustrates the sampling device 10 when the latch 52 is supported by the ledges 64 o~ the retaining members 60.
When the user hears the audible click generated by the retaining members 60 snapping against the latch 52, the user knows that the sampling device 10 is in a retracted, ready state. A bore 100 may optionally be ~ormed in the knob 30 so that the user can visually determine that the sampling device is in the ready state by 10 seeing the top end o~ the shaft 50 in the bore 100. The user then allows the knob 30 to be moved downwards, under the in~luence o~ the spring 36 (which is optional), until a pair o~ angled sur~aces 96 on the internal underside o~ the knob 30 abut the top angled sur~aces o~ the retaining members 60 (as shown in the upper portion o~ Fig.
1).
When the sampling device 10 is in the ready state, the lancet sha~t 42, the lancet holder 44, and the plunger 48 are in a retracted position located a relatively large distance inwardly ~rom the bottom end o~ the sampling device 10, and the spring 51 is compressed to a relatively large degree. Also, the enlarged annular portion 94 o~ the rubber plunger 96 is positioned within the suction chamber 88 at a point near the top o~ the suction chamber portion 88a.
To draw the blood sample, the user ~irst positions the bottom end of the sampling device 10 ~irmly against the skin where the blood sample is to be taken so that a relatively air-tight seal is ~ormed between the bottom end o~ the sampling device and the skin.
To ~acilitate the ~ormation o~ an air-tight seal, an annular rubber washer or sealing member 97 may be provided on the bottom o~ the end cap 20, and the sealing member 97 may be wetted. Alternatively, the bottom o~ the end cap 20 may be provided with an annular lip to ef~ect the seal.
With the sampling device 10 pressed against the skin, the user then forces the knob 30 downwards until the annular ~lange 38 on the bottom o~ the actuator 32 makes contact with a relatively sti~f spring 98 supported by an annular spring holder 99, at which point the angled sur~aces 96 on the knob 30 have spread apart the retaining members 60 to a su~icient extent so that the latch 52 is released by the ledges 64. When that occurs, the bore in the sealing member 72 will be sealed by the relatively large bottom portion 84 o~ the venting peg 80 so that the upper end o~ the suction chamber 88 is substantially air-tight.
When the latch 52 is released, the compressed spring 51 will force the plunger hub 48, the lancet holder 44, and the lancet sha~t 42 downwardly. As the plunger hub 48 moves downwardly, the downward movement o~ the enlarged portion 94 o~ the rubber plunger 46 within the suction chamber portion 88a will cause a reduced air pressure or partial vacuum within the suction chamber 88 since air cannot enter the suction chamber 88 ~rom other points.
It should be noted that the acceleration o~ the lancet holder 44 and lancet sha~t 42 is somewhat damped when the plunger 46 is moving within the suction chamber portion 88a since the partial vacuum being ~ormed within the suction chamber 88 will exert an upward ~orce on the lancet holder 44 (the ~riction ~rom the annular portion 94 will also damp the acceleration). The acceleration o~
the lancet holder 44 and lancet sha~t 42 is not damped due to a positive pressure buildup in the internal portions of the sampling device 10 below the suction chamber 88 since any excess air pressure is vented out o~ the sampling device 10 via the one-way check valve 26.

When the enlarged portion 94 o~ the rubber plunger 46 passes ~rom the suction chamber portion 88a to the larger acceleration chamber 92, the rate o:E acceleration o~ the lancet holder 44 and lancet shai~t 42 will increase due to: 1) decreased ~riction generated by the rubber plunger 46 since the enlarged portion 94 oE
the plunger 46 no longer makes signi~icant contact with any internal sur~ace o~ the sampling device 10, and 2) the equalization o~ air pressures above and below the plunger 46.
With respect to 2), it should be noted that, when the plunger 46 passes Erom the suction chamber portion 88a to the acceleration chamber 92, the partial vacuum i~ormed in the suction chamber 88 will be somewhat reduced by air entering the suction chamber 88 from below the plunger 46. However, a partial vacuum will still exist within the sampling device 10 since no air enters the lower interior portion o~ the sampling device 10 ~rom the outside.
The lancet holder 44 and lancet shai~t 42 continue to accelerate until the latch 52 makes contact with the annular disk support by the spring 70, at which point the spring 70 starts to decelerate the lancet holder 44 and lancet sha~t 42. The lancet holder 44 and lancet shai~t 42 move downwardly until the bottom sur~ace oi~ the lancet holder 44 makes contact with an annular stopping ~lange 101 integrally ~ormed on the interior o~ the sleeve 18. The depth o~
the skin puncture made by the lancet 40 may be adjusted within a range, ~or example, o~ 0. 5 millimeters to 2.5 millimeters by rotating the end cap 20, which rotation varies the distance between the bottom o~ the end cap 20 and the stopping i~lange 101.
When the lancet 40 pierces the skin, blood will be drawn into the bottom end o~ the sampling device 10 due to the partial vacuum ~ormed therein. A~ter the skin is punctured, the lancet 40 iS
retracted back into the sampling device 10 by the spring 70, which ~orces the lancet holder 44 and lancet sha~t 42 upwards. Blood will be drawn into the sampling device 10 until the user vents the sampling device 10 to eliminate the partial vacuum. The partial vacuum may have a magnitude o~ approximately 0.5 Bar below atmospheric pressure. To achieve that partial vacuum, the dead volume around the lancet should be minimized. One or more enlarged annular flanges 103 may be ~ormed on the lancet holder 42 to reduce the internal volume within the bottom end o~ the sampling device 10.
Alternatively, the lancet holder 42 may be provided with a larger, constant diameter to reduce the dead volume within the sampling devlce .
The sampling device o~ Fig. 1 is vented by the user by pressing the knob 30 downwards against the relatively sti~ spring 98 so that the venting plug 80 occupies the position shown in Fig. 5. When that occurs, air will ~low ~rom the upper interior portion o~ the sampling device 10 into the lower interior portion o~ the sampling device 10 where the partial vacuum exists. It should be noted that the upper interior portion o~ the sampling device 10 is in ~luid communication with the outside due to an annular space ~ormed between the actuator 32 and the sur~ace 35 o~ the upper housing portlon 14.
A portion o~ an alternative embodiment o~ the sampling device is illustrated in Fig. 6. The alternative sampling device utilizes a di~erent mode o~ venting the interior o~ the sampling device 10 a~ter the blood sample is drawn. Unless otherwise indicated below in connection with Fig. 6, the ~eatures o~ the alternative sampling device are identical to those o~ the sampling device 10 described above in connection with Figs. 1-4.
Re~erring to Fig. 6, the alternative sampling device utilizes a constant-diameter venting peg 110 that is connected to the bottom portion o~ the actuator 32. The venting peg 110 is movable between a non-venting position (shown in Fig. 6) in which it blocks the bore ~ormed in the sealing member 72 and a venting position in which the venting peg 110 is disposed above the bore in the sealing member 72 so that air may vent through the bores. When the venting peg 110 is in its non-venting position, its bottom end abuts an end stop, which may be in the ~orm o~ a horizontal interior sur~ace 112 o~ the main body 12 (the cylindrical well 86 o~ Fig. 1 is eliminated).
~lternatively, the end stop may be composed o~ a harder material.
In the alternative sampling device, the spring 98 must be stronger than the actuator return spring 36 so that the venting peg 110 is normally held in its venting position above the bore in the sealing member 72. The length o~ the venting peg 110 is selected so that the latch 52 is not released by the retaining arms 30 until the venting peg 110 reaches its non-venting position.
To operate the alternative sampling device, a~ter the latch 52 was released by the retaining members 30, the user would gently ~orce the knob 30 downwardly against the ~orce o~ the spring 98 to keep the venting peg 110 in its non-venting position while the blood sample was being withdrawn. To vent the device, the user would simply release the knob 30, so that the spring 98 would ~orce the venting peg 110 upwards ~rom its non-venting position to its venting position. This alternative sampling device may be pre~erred since the construction o~ the venting peg is simpli~ied and since a relatively large ~orce is required to vent the sampling device o~
Fig. 1 to prevent accidental venting.
Modi~ications and alternative embodiments o~ the invention will be apparent to those skilled in the art in view of the ~oregoing description. This description is to be construed as illustrative only, and is ~or the purpose o~ teaching those skilled in the art the best mode o~ carrying out the invention. The details o~ the structure and method may be varied sub~tantially without departing ~rom the spirit of the invention, and the exclusive use o~ all modi~ications which come within the scope o~ the appended claims is reserved.

Claims

1. A blood sampling device, comprising:
a housing (12, 14, 18, 20);
a shaft (50) disposed in said housing (12, 14, 18, 20);
a lancet (40) operatively coupled to said shaft (50), said lancet (40) being movable between a retracted position in which said lancet (40) is disposed within said housing (12, 14, 18, 20) and an extended position in which said lancet (40) extends outside of said housing (12, 14, 18, 20);
means (50, 52, 60, 64) for retaining said lancet (40) in said retracted position;
means (51) for causing said lancet (40) to automatically move from said retracted position to said extended position; and means for generating a reduced internal pressure within an area in said housing (12, 14, 18, 20) as said lancet (40) moves from said retracted position to said extended position to facilitate drawing blood from a skin puncture to be made by said lancet (40) into an interior portion of said housing (12, 14, 18, 20), said internal pressure being less than an ambient pressure outside of said housing (12, 14, 18, 20), said means for generating a reduced internal pressure comprising:
a suction chamber (88) disposed in said housing (12, 14, 18 , 20), said suction chamber (88) having a diameter and a substantially air-tight end;
an acceleration chamber (92) disposed in said housing (12, 14, 18, 20) and being disposed generally coaxially with said suction chamber (88), said acceleration chamber (92) having a diameter larger than said diameter of said suction chamber (88); and a plunger (46) connected to said shaft (50), said plunger (46) having an exterior portion (94) which makes sealing contact with said suction chamber (88) so that said reduced internal pressure is formed within said suction chamber (88) when said plunger (46) is moved in a direction away from said substantially air-tight end of said suction chamber (88), said exterior portion (94) of said plunger (46) having a diameter smaller than said diameter of said acceleration chamber (92) to facilitate acceleration of said shaft (50) towards said extended position.

2. A device as defined in claim 1 wherein said means (50, 52, 60, 64) for retaining said lancet (40) in said retracted position comprises a latch mechanism (52).

3. A device as defined in claim 1 wherein said means for causing said lancet (40) to automatically move from said retracted position to said extended position comprises a spring (51).

4. A device as defined in claim 1 additionally comprising means (80) for venting said reduced internal pressure area to increase said reduced internal pressure.

5. A device as defined in claim 1 additionally comprising means (70) for decelerating said lancet (40) as said lancet (40) moves towards said extended position.

6. A device as defined in claim 1 additionally comprising a check valve (26) in fluid communication with said acceleration chamber (92) to allow air to pass from said acceleration chamber (92) to a point outside of said housing (12, 14, 18, 20).

7. A blood sampling device, comprising:
a housing (12, 14, 18, 20);
a shaft (50) disposed in said housing (12, 14, 18, 20);
a lancet (40) operatively coupled to said shaft (50), said lancet (40) being movable between a retracted position in which said lancet (40) is disposed within said housing (12, 14, 18, 20) and an extended position in which said lancet (40) extends outside of said housing (12, 14, 18, 20);
means (50, 52, 60, 64) for retaining said lancet (40) in said retracted position;
means (51) for causing said lancet (40) to automatically move from said retracted position to said extended position; and means for generating a reduced internal pressure within an area in said housing (12, 14, 18, 20) as said lancet (40) moves from said retracted position to said extended position to facilitate drawing blood from a skin puncture to be made by said lancet (40) into an interior portion of said housing (12, 14, 18, 20), said internal pressure being less than an ambient pressure outside of said housing (12, 14, 18, 20).

8. A device as defined in claim 7 additionally comprising a check valve (26) in fluid communication with said acceleration chamber ( 92) to allow air to pass from said acceleration chamber (92) to a point outside of said housing (12, 14, 18, 20).

9. A blood sampling device, comprising:
a housing (12, 14, 18, 20);

a shaft (50) disposed in said housing (12, 14, 18, 20);
a lancet (40) operatively coupled to said shaft (50), said lancet (40) being movable between a retracted position in which said lancet (40) is disposed within said housing (12, 14, 18, 20) and an extended position in which said lancet (40) extends outside of said housing (12, 14, 18, 20);
means (50, 52, 60, 64) for retaining said lancet (40) in said retracted position;
means (51) for causing said lancet (40) to automatically move from said retracted position to said extended position; and means for generating a reduced internal pressure within an area in said housing (12, 14, 18, 20) as said lancet (40) moves from said retracted position to said extended position to facilitate drawing blood from a skin puncture to be made by said lancet (40) into an interior portion of said housing (12, 14, 18, 20), said internal pressure being less than an ambient pressure outside of said housing (12, 14, 18, 20), said means for generating a reduced internal pressure comprising:
a bore (88) disposed in said housing (12, 14, 18, 20) and having a substantially air-tight end; and a plunger (46) connected to said shaft (50), said plunger (46) having an exterior portion (94) which makes sealing contact with said bore (88) so that said reduced internal pressure is formed within said bore (88) when said plunger (46) is moved in a direction away from said air-tight end of said bore (88).

10. A device as defined in claim 9 additionally comprising a check valve (26) in fluid communication with said acceleration chamber (92) to allow air to pass from said acceleration chamber (92) to a point outside of said housing (12, 14, 18, 20).