WO1992016144A1

WO1992016144A1 - Body fluid extraction device

Info

Publication number: WO1992016144A1
Application number: PCT/AU1992/000105
Authority: WO
Inventors: Darryl Gordon Robb
Original assignee: Goldspill Pty. Ltd.
Priority date: 1991-03-15
Filing date: 1992-03-10
Publication date: 1992-10-01

Abstract

A device (1) for extracting body fluid in which depression of a plunger (4) into a tubular body (2) during a preparatory stroke creates a pressure reduction in a first chamber (12). After the preparatory stroke, the pressure reduction in the first chamber (12) exerts a force on a piston (3) to cause it to move and thereby to draw body fluid into a second chamber (15). The rate of extraction of the body fluid is governed by a frictional force on the plunger (4) which can be controlled by a cam arrangement (5).

Description

BODY FLUID EXTRACTION DEVICE

Field of the Invention

The present invention relates to devices for extracting body fluid, and more particularly to a device for extracting body fluid in which a pressure reduction is created by depression of a piston into a tubular body, and the pressure reduction so created is used to draw fluid into the tubular body. Background A conventional apparatus for extracting a body fluid, such as blood from a patient, usually comprises a cannula and an evacuated vial which is sealed with a rubber-like membrane. It is common practice to extract the body fluid by inserting a first end of the cannula into a part of the patient's body which contains the body fluid, followed by piercing the rubber-like membrane with a second end of the cannula. Body fluid is then drawn through the cannula into the evacuated vial.

A first disadvantage of the conventional apparatus for body fluid extraction is that the rate of flow of body fluid into the evacuated vial cannot be accurately and easily controlled, but depends on such parameters as the diameter of the cannula and the pressure inside the evacuated tube. In the case of blood extraction, it is desirable to control the rate of extraction, especially from weak patients, to avoid causing the patient's blood vessels to collapse.

A second disadvantage of the conventional apparatus for body fluid extraction is that it is potentially hazardous. In order that they may have sufficient strength to sustain a required low internal pressure, the evacuated vials are usually constructed from glass. However, this presents a potential hazard because glass vials can be shattered easily to expose sharp edges which can cut workers or technicians. This can be especially dangerous when the vials contain hazardous substances such as blood infected with viruses.

A third disadvantage of the conventional apparatus for body fluid extraction is that it requires the maintenance of a stock of evacuated vials. Over time, the low pressures in such vials may degrade such that the vials may not be effective in receiving body fluid.

A fourth disadvantage of the conventional apparatus for body fluid extraction is that the evacuated vial cannot be pre-filled easily and accurately to predetermined levels with such fluids as anticoagulants or agents for separating red and white blood cells.

A fifth disadvantage of the conventional apparatus for body fluid extraction is that, once the body fluid is extracted, withdrawal of a sample of the body fluid from the evacuated vial for analysis can be difficult or dangerous. To withdraw a sample from the conventional apparatus, one end of the evacuated vial is usually removed, and the sample is sucked into a pipette. This can lead to spread of disease. Summary of the Invention

In preferred embodiments the present invention overcomes at least some of the above deficiencies of conventional body fluid extraction devices. According to one broad form of the invention, there is provided a device for extracting body fluid having a syringe-type construction. The device includes a tubular body having a proximal end, a distal end, and a bore.

A piston is disposed within the bore. The piston has a proximal face, a distal face, and an outer face which is in slidable contact with the bore.

A plunger, which has a shank, is mounted slidably at the proximal end of the tubular body and removably attached to the proximal face of the piston for pushing the piston from the proximal end of the tubular body towards the distal end of the tubular body during a preparatory stroke in which external pressure is applied to the plunger.

A sealing means is used to seal the shank slidably to the proximal end of the tubular body so as to form a first chamber defined by the bore, the shaft, the proximal face of the piston and the distal face of the sealing means. A pressure reduction is formed in the first chamber during the preparatory stroke of the plunger. Closure means are provided to close the distal end of the tubular body so as to form a second chamber defined by the bore, the distal face of the piston and the closure means. The closure means is adapted to cooperate with filling means which places the body fluid in communication with the second chamber.

After the preparatory stroke when external pressure is removed from the plunger, the pressure reduction in the first chamber causes the piston to move towards the proximal end of the tubular body and to draw the body fluid into the second chamber.

The rate of extraction of body fluid is preferably made controllable by providing a cam arrangement in which rotation of the sealing means causes a variation of a frictional force on the plunger. Non-circular cross sections are preferably provided on a lip at the proximal end of the tubular body and to a groove around an outer surface of the sealing means which engages with the lip. The sealing means can be rotated within the lip about an axis of rotation. The sealing means is constructed from a compressible elastic material such that, during rotation, its motion relative to the lip, combined with the non-circular cross sections, causes a variation in an internal pressure in the compressible elastic material. The magnitude of the internal pressure is determined by an angle of rotation of the sealing means relative to the lip. The shaft of the plunger passes through a hole in the sealing means so that the internal pressure is communicated as a controllable pressure of the sealing means on the shaft. This results in a controllable frictional force between the sealing means and the shaft, and this retards the rate of movement of the plunger, the rate of movement of the piston, and the rate of body fluid extractio .

In a preferred embodiment of the invention a bung is situated within the bore between the piston and the distal end of the tubular body and constitutes the closure means. The bung has an outer wall which is in slidable contact with the bore, so as to form the second chamber defined by the bore, the distal face of the piston, and the bung. At the end of the preparatory stroke, an arresting means retains the bung at the distal end of the tubular body.

In the abovementioned preferred embodiment, the arresting means which retains the bung at the distal end of the tubular body preferably comprises a circumferential rib around the bore and a circumferential groove around the outer wall of the bung. The bung is constructed from an elastic material and has a distal surface with a generally convex shape so that, during the preparatory stroke, the distal surface passes the circumferential rib. At the end of the preparatory stroke, the circumferential rib is substantially aligned with the circumferential groove. The circumferential rib has a cross section with an acute edge proximate the distal end of the tubular body. The acute edge engages with the circumferential groove so as to impede the movement of the bung towards the proximal end of the tubular body, and thus acts to retain the bung at the distal end of the tubular body. In this way, a body fluid extraction device is provided in which the rate of body fluid extraction can be controlled easily and accurately. In addition, the body fluid extraction device can be constructed from a plastic-like material so that hazards due to shattering of evacuated vials are eliminated. Further, the pressure reduction in the first chamber need only be created immediately before the device is to be used; thus avoiding the problems due to loss of low pressure in the evacuated vial. The device can be pre-filled easily and accurately to predetermined levels with fluids such as anticoagulant agents. Finally, samples containing precise amounts of body fluid can be withdrawn from the body fluid extraction device because a cannula can be fitted to the distal end of the tubular body, and the fluid can be expelled from the device in the same way that fluids can be expelled from a hypodermic syringe. Brief Description of the Drawings

The invention will now be further described with reference to the accompanying drawings in which: Fig. 1 is a longitudinal section of a body fluid extraction device in accordance with a preferred embodiment of the invention in which the device is shown before use;

Fig. 2 is a longitudinal section of the body fluid extraction device of Fig. 1 in which the device is shown at the end of a preparatory stroke;

Fig. 3 is a longitudinal section of the body fluid extraction device of Fig. 1 in which the device is shown after body fluid has been extracted; Fig. 4 is an end view of a sealing means adapted to fit into a proximal end of the body fluid extraction device of Fig. 1, viewed from the proximal end of the device;

Fig. 5 is an end view of the body fluid extraction device of Fig. 1, viewed from the proximal end of the device;

Fig. 6 is a longitudinal sectional view of a needle like device which can be utilised in the withdrawal of body fluid from the body fluid extraction device; and Fig. 7 is a longitudinal section of a body fluid extraction device according to a second embodiment of the invention in which the device is shown before use. Detailed Description of the Preferred Embodiment

Figs. 1 to 3 show an illustrative embodiment of the body fluid extraction device 1 which comprises syringe-like tubular body 2, piston 3, plunger 4, sealing means 5, and bung 6. Bore 7 is situated inside tubular body 2 and extends from proximal end 8 to distal end 9. Bore 7, piston 3, plunger 4, and bung 6 all have longitudinal axes which are substantially coincident. Piston 3 is disposed within tubular body 2 in slidable contact with bore 7 and is shaped so as to form a substantially air-tight seal against bore 7.

Plunger 4 is removably attached to proximal face 10 of piston 3 and extends out of proximal end 8 of tubular body 2 through hole 11 in sealing means 5.

Sealing means 5 forms substantially air-tight seals against bore 7 and plunger 4. In addition circular lip 23 surrounding the proximal end of body 2 is sealingly engaged by groove 22 in sealing means 5. Plunger 4 can slide through hole 11 while retaining a substantially air-tight seal with sealing means 5.

First chamber 12 is defined by proximal face 10 of piston 3, bore 7, plunger 4, and face 13 of sealing means 5. The position of piston 3 relative to proximal end 8 defines a volume of first chamber 12.

Bung 6 is disposed within tubular body 2 in slidable contact with bore 7 between distal face 14 of piston 3 and distal end 9 of tubular body 2. Bung 6 is shaped so as to form a substantially air-tight seal against bore 7. Distal face 14 of piston 3, tubular body 2, and bung 6 define second chamber 15 in which body fluid is to be collected and temporarily stored and into which anti-coagulants and other reagents may be pre-filled. Fig. 1 shows body fluid extraction device 1 in a state before use. In this state, proximal face 10 of piston 3 is close to sealing means 5 so that the volume of first chamber 12 is small.

Body fluid extraction device 1 is prepared for use by a preparatory stroke in which external pressure is applied to plunger 4 along longitudinal axis 16 of tubular body 2 to cause plunger 4, piston 3, and bung 6 to move away from proximal end 8 toward distal end 9.

During the preparatory stroke, the movement of piston 3 causes the volume of first chamber 12 to increase. Because sealing means 5 forms substantially air-tight seals with tubular body 2 and plunger 4, substantially no air enters first chamber 12, and so the increase of the volume of that chamber causes a pressure decrease there.

At, or close to, the end of the preparatory stroke, plunger 4, piston 3, and bung 6 reach the position shown in Fig. 2. At this position, an arresting means impedes the movement of bung 6 so that it cannot move freely back toward proximal end 8.

Preferably, the arresting means comprises circumferential rib 17 around bore 7 and circumferential groove 18 around the outer wall of bung 6. Bung 6 is constructed from an elastic material and has a distal surface 19 with a generally convex shape so that, during the preparatory stroke, distal surface 19 passes circumferential rib 17. At the end of the preparatory stroke, circumferential rib 17 is substantially aligned with circumferential groove 18. Circumferential rib 17 has a cross section with an acute edge 20 proximate distal end 9 of tubular body 2. Acute edge 20 engages with circumferential groove 18 so as to impede the movement of bung 6 back towards proximal end 8 of tubular body 2, and thus acts to retain bung 6 at distal end 9. With the device in the state illustrated in Fig. 2, a filling means allows body fluid such as blood to be brought into fluid contact with second chamber 15. Preferably, the filling means comprises cannula 21 as shown in Figs. 2 and 3. When distal end 9 is brought into contact with cannula 21, bung 6 is pierced; thus preparing a path for body fluid to flow into second chamber 15.

After the preparatory stroke, external pressure is removed from plunger 4. The pressure reduction in first chamber 12 exerts an attractive force on proximal face 10 of piston 3 to cause it to move toward proximal end 8 and away from distal end 9. This movement of piston 3, together with the arrested position of bung 6, creates a pressure reduction in second chamber 15 which causes body fluid to be drawn into that chamber. As second chamber 15 fills with body fluid, piston 3 and plunger 4 move away from distal end 9 toward proximal end 8. When piston 3 reaches a position sufficiently close to proximal end 8, the body fluid extraction ceases. At this point, the cannula 21 may be removed, and plunger 4 may be removed from piston 3. In this way, second chamber 15 forms a substantially sealed container for holding body fluid.

The rate of extraction of body fluid can be controlled, for example, by governing the rate at which plunger 4 (and hence piston 3) are allowed to move back towards proximal end 8. In the preferred embodiment, this rate is governed by a cam arrangement which can be used to adjust a frictional force exerted on plunger 4 by sealing means 5. As illustrated in Figs. 4 and 5, such a frictional force can be rendered adjustable by providing on sealing means 5 a body portion 35 having a non-circular outer cross section, and a similar non-circular inner cross section to a portion 34 of the tubular body 2 proximal end 8 of tubular body 2. Body portion 35 has a large dimension 24 and a small dimension 25. Similarly, portion 34 of the tubular body has a large dimension 26 and a small dimension 30.

Sealing means 5 is constructed from a compressible elastic material such that any attempt to deform its outer surface results in a variation of an internal pressure within the compressible elastic material. Plunger 4 passes through hole 11 in sealing means 5 so that the internal pressure is communicated as a pressure of sealing means 5 on plunger 4. This results in a frictional force between sealing means 5 and plunger 4 which retards its rate of movement.

Sealing means 5 can be rotated within portion 34 of the tubular body 2 about longitudinal axis 16. When sealing means 5 is rotated relative to portion 34 of tubular body 2 such that large dimensions 26 and 24 are substantially collinear. The internal pressure in sealing means 5 is a minimum. However, when sealing means 5 is rotated relative to portion 34 of tubular body 2 such that large dimension 26 is substantially collinear with small dimension 30, the internal pressure in sealing means 5 is a maximum.

Thus, by varying an angle of rotation of sealing means 5 relative to tubular body 2, a user of the device can control the amount of pressure exerted by sealing means 5 on plunger 4. This results in a controllable frictional force between sealing means 5 and plunger 4 which controllably retards the rate of movement of plunger 4, the rate of movement of piston 3, and the rate of body fluid extraction. After body fluid extraction device 1 is filled, as illustrated in Fig. 3, cannula 21 and plunger 4 can be removed to form a substantially sealed container in which body fluid can be stored. Samples of body fluid can be withdrawn from body fluid collection device 1 using several methods. A first method comprises the steps of inserting a needle, cannula or similar device through bung 6 into second chamber 15 containing the body fluid, attaching a plunger to proximal face 10 of piston 3, and applying external pressure along longitudinal axis 16 so as to move piston 3 towards distal end 9 and to expel body fluid through the cannula. Circumferential rib 17 around bore 7 is provided with acute edge 20 to engage with circumferential groove 18 around the outer surface of bung 6 to ensure that the insertion of a cannula or the like through bung 6 does not cause the bung to move into bore 7 toward proximal end 8, but instead causes acute edge 20 to further engage with circumferential groove 18. Preferably, acute angle 20 is thirty degrees.

Fig 6 shows a preferred form of a needle-like device 27 for insertion through bung 6 to allow withdrawal of body fluid from second chamber 15. Device 27 is circular in cross-section and has a bore 28 extending axially through it. A first end portion 29 of device 27 is of narrow external diameter and is sharpened to point 31. Second end portion 32 is frustoconical in shape. An annular ridge 33 is formed between first and second end portions 29 and 32. In use first end portion is pushed through bung 6. The body fluid in second chamber 15 may be expressed through bore 28 by depressing plunger 4 and thus piston 13. This form of device has the advantage that after communication has been established with the contents of the second chamber 15 there are no sharp edges projecting from device 1 on which a user could be cut. A second method of withdrawing a sample of body fluid from body fluid extraction device 1, for which method piston 3 is constructed from a penetrable material, comprises the steps of inserting a cannula attached to a suitable sampling device such as a hypodermic syringe through hole 11 in sealing means 5 and through piston 3 into second chamber 15, and to withdraw body fluid into the sampling device. Circumferential ledge 28 around bore 7 engages with circumferential slot 29 around the outer surface of piston 3 to ensure that the insertion of the cannula through piston 3 does not cause that piston to move into bore 7 toward distal end 9.

Before- use, body fluid extraction device 1 can be operated as a hypodermic syringe to pre-fill tubular body 2 with fluids such as anticoagulants or agents for separating red and white blood cells.

Fig. 7 shows a fluid or blood extracting device quite similar to that of the device shown in Fig. 1 but includes a plug 114 which is screwed, by screw thread 116, into sealing engagement with end 93 of body 91 at the tapered matching surfaces 115. Plug 114 also provides an air seal about plunger 96 at cylindrical region 114.

Plug 114 frictionally grips plunger 96 at cylindrical portion 117, the frictional grip being adjustable by way of adjusting the screw pressure applied to plug 114. Tight screw pressure applied to plug 114 results in tapered surfaces 115 radially compressing the volume of plug 114 that surrounds portion 117, thus increasing the frictional grip between plug 114 and plunger 96. By reducing the screw force applied to plug 114, but not so much as to violate the seal at surfaces 115, the radial pressure applied to surface portion 117 is reduced and the frictional grip reduced.

In the arrangement of Fig. 7 engagement portion 98 of plunger 96 comprises a cylindrical boss separated from the remainder of plunger 96 by a groove. Engagement portion 98 is resiliently gripped by piston head 95 which is made of rubber or some similar elastomeric material. Immediately before use the device is in the configuration as illustrated in Fig. 7. Cap 112 is removed and a suitable cannular inserted into sleeve 111.

Piston head 95 is then pressed fully down to end 94, by applying pressure to handle 97. By virtue of the seal applied by plug 114 at surface area 118 with plunger 96 and at surfaces 115 with body 91, a substantially evacuated volume is formed between piston head 95 and plug

114.

With piston head 95 fully depressed to end 94, the cannular is inserted into the appropriate vessel and by releasing the pressure applied to handle 97, the evacuated volume behind piston head 95 will retract piston head 5 back toward end 93 and thus allow the collection of the blood sample within the device. The speed of retraction of piston head 95 can be adjusted by adjusting the screw tensioning of plug 114. Thus the device will provide a smooth rate of retraction of piston head 95 at an adjustable speed.

Plug 114 will serve to prevent the complete removal of piston head 95, after removal of the cannular the cap 112 is replaced over sleeve 111, and the sample of blood or other fluid, is now ready for safe and convenient transportation or storage.

Claims

CLAIMS:-

1. A device for extracting body fluid comprising: a tubular body having a proximal end, a distal end, and a bore; a piston disposed within the bore, the piston having a proximal face, a distal face, and an outer face, the outer face being in slidable contact with the bore; a plunger mounted slidably at the proximal end of the tubular body and removably attached to the proximal face of the piston for pushing the piston from the proximal end of the tubular body towards the distal end of the tubular body during a preparatory stroke in which an external pressure is applied to the plunger, the plunger having a shank; sealing means for slidably sealing the proximal end of the tubular body to the shank of the plunger so as to form a first chamber defined by the bore, the shaft, the sealing means, and the proximal face of the piston, so that a pressure reduction is formed in the first chamber during the preparatory stroke of the plunger; closure means to close the distal end of the tubular body so as to form a second chamber defined by the bore, the distal face of the piston and the closure means; the closure means is adapted to cooperate with filling means for placing the body fluid in fluid communication with the second chamber so that, after the external pressure is removed from the plunger, the pressure reduction in the first chamber causes the piston to move towards the proximal end of the tubular body and to draw body fluid into the second chamber.

2. A device for extracting body fluid as claimed in claim 1 in which the closure means comprises a bung situated within the bore between the piston and the distal end of the tubular body, the bung having an outer wall in slidable contact with the bore, so as to form the second chamber defined by the bore, the distal face of the piston, and the bung and in which arresting means are provided for retaining the bung at the distal end of the tubular body after the preparatory stroke;

3. A device for extracting body fluid as claimed in claim 1 or claim 2 wherein the sealing means is constructed from a compressible elastic material, the shaft of the plunger passes through a hole in the sealing means, and the device for extracting body fluid includes a cam arrangement which comprises: a first cam means for creating a controllable deformation of the sealing means; and a second cam means for cooperating with the first cam means to create the controllable deformation of the sealing means, the second cam means being rotatably engaged with the first cam means such that relative rotation of the second cam means with respect to the first cam means causes the controllable deformation of the sealing means and a corresponding controllable internal pressure in the compressible elastic material, thereby creating a controllable frictional force to be applied to the shaft of the plunger to enable the body fluid to be extracted at a controllable rate.

4. A device for extracting body fluid as claimed in claim 3 in which the first cam means has a non-circular inner cross section and the second cam means has a non-circular outer cross section.

5. A device for extracting body fluid as claimed in claim 4 wherein the first cam means comprises a lip at the proximal end of the tubular body.

6. A device for extracting body fluid as recited in claim 4 wherein the second cam means comprises a groove around an outer surface of the sealing means.

7. A device for extracting body fluid as recited in claim 2 wherein the bung is constructed from an elastic material and has a distal surface with a generally convex shape and the arresting means comprises: a circumferential rib around the bore proximate the distal end of the tubular body; and a circumferential groove around the outer wall of bung so that, at the end of the preparatory stroke, the circumferential rib is substantially aligned with the circumferential groove so as to impede a movement of the bung towards the proximal end of the tubular body.

8. A device for extracting body fluid as claimed in claim 5 wherein the circumferential rib has an acute edge proximate the distal end of the tubular body.

9. A device for extracting body fluid as claimed in claim 1 wherein the device includes filling means comprising a needle, cannula or similar device which is removably attached to the distal end of the tubular body.

10. A device for extracting body fluid as claimed in claim 1 wherein the piston is constructed from a penetrable material and samples of body fluid may be withdrawn by inserting a cannula through the piston.