WO1991005511A1

WO1991005511A1 - Improvements in blood sampling

Info

Publication number: WO1991005511A1
Application number: PCT/GB1990/001562
Authority: WO
Inventors: Gerrard Abdool Rayman
Original assignee: Gerrard Abdool Rayman
Priority date: 1989-10-14
Filing date: 1990-10-10
Publication date: 1991-05-02
Also published as: GB2236680A; AU6620890A; GB9021948D0; GB8923210D0

Abstract

A blood sampling technique comprises adhering an apertured sticky pad (3) to the skin and pricking the skin through the aperture in the pad so that blood exudes into and is retained in the pad aperture (10) for collection, either by a portable collecting device or by a blood-porous layer (9) on the pad behing the adhesive layer (8).

Description

Title Improvements in Blood Sampling

Field of the invention

This invention relates generally to blood sampling and is particularly concerned with a method of and apparatus for taking a small sample of blood from a pin prick, for exampl e on a fi nger .

Background to the invention

At present, rather crude methods are employed. Commonly, the finger is pricked and then the end of a capillary tube is held against the skin at the point of the prick in an endeavour to attract a small quantity of blood, say two or three drops, into the tube. To encourage the blood to appear, the finger may be massaged or squeezed. However, the blood collecting step is very uncertain, because the blood, when it does appear, may not appear directly under the end of the tube and may quickly run away around the finger.

The invention

According to the present invention, in its broadest aspect, there is provided a method of taking a blood sample according to which an apertured adhesive pad is applied to the skin, and the skin is pricked through the aperture in the pad so that the escape of blood is

confined to a collecting area formed by the aperture in the pad. It is important for the sticky pad to form a tight seal with the skin, ensuring that escape o f blood is confined to the aperture in the pad and that the blood is not spilled to other areas.

In one method, especially suitable where the subject is taking the blood sample personally, blood is collected from the aperture in the pad by a blood porous layer of the pad behind the adhesive layer.

More generally, the blood is collected from the aperture in the pad by a portable collecting device, such as a capillary tube.

The invention also provides apparatus for carrying out the afore-described methods.

Thus, in one aspect, there is provided apparatus

comprising an adhesive pad having a generally central aperture, an impervious adhesive layer on one face and a thicker layer of blood-porous material behind the adhesive layer.

In another aspect, there is provided apparatus comprising an adhesive pad having a generally central blood- collecting aperture and an adhesive layer on one face, together with a portable collecting device having a forward end adapted to enter the aperture in the pad to withdraw blood therefrom. In this case, the layer of pad behind the adhesive layer is preferably of low porosity to blood.

Preferably, the pad aperture and the forward end of the capillary tube are mutually adapted to locate the

extremity of the forward end of the tube against the skin.

In an embodiment, the capillary tube has a vent hole at an intermediate point in its length, together with a plunger inserted in the rear end of the tube.

Thus, in use of this embodiment, the apertured pad is applied to the skin and a pricker, such as that made and sold by Owen Mumford Limited under the Registered Trade Mark AUTOLET, is used to prick the skin through the pad aperture at the point where the capillary tube end is to be located. The forward end of the tube is then applied at this point, with the plunger withdrawn sufficiently to expose the vent hole. This allows capillary action to take place, and the tube will partially fill to a point near the vent hole as blood collects in the pad aperture. The tube and its plunger need not be held during this time; the engagement of the forward end of the tube with the pad is sufficient to support the assembly. If necessary, the finger can be squeezed or massaged to assist the supply of blood.

When the sample has been taken, the tube is removed and taken to wherever it is to be dispensed. This operation is done by the plunger, and as its end moves past the vent hole, air can no longer vent and so the sample is forced out of the tube. The plunger may be provided with a stop that will eventually cooperate with the rear end of the tube and thus give a predetermined effective stroke for the plunger, resulting in a measured quantity of blood sample being dispensed, which is important for some blood tests. The forward end of the tube ay be slightly tapered, enabling it to be pushed into the pad aperture more easily.

The preferred pad will be of a composite construction with a thin skin-sealing adhesive skin forming one face backed by a thicker layer, possibly of smaller area and possibly of closed cell foam with a slight resilience. The aperture in the pad at which the blood collects may be slightly smaller than the main portion of the capillary tube, so that when the forward end of the tube is pressed in, the tube will be firmly gripped and retained, more especially to render the tube self-supporting.

Description of embodiment

The invention is exemplified with reference to the

accompanying drawings, in which:-

Figure 1 is mostly a longitudinal section of one

embodiment of a blood sampling device in the condition as applied to the skin;

Figure 2 is another longitudinal section of the device, to a smaller scale, containing a blood sample;

Figure 3 is a longitudinal section of the device having just dispensed a sample; and

Figure 4 is a transverse cross-section through an

adhesive pad.

The exemplified blood sampling device comprises a capillary tube 1 with a plunger 2 inserted in one end and with an adhesive pad 3 for application to and sealing against the subject's skin. The tube 1, which is

preferably of clear plastics material, is slightly tapered at its leading end 4, and at an intermediate point it has a vent hole 5. The plunger 2 is basically a straight rod, also of plastics material, with a close sliding fit in the tube 1, but with a finger pad 6 at its free end and a stop 7 in the form of a collar at an intermediate point. The pad 3 consists of an adhesive film 8 with a generally non-porous and slightly resilient foam layer 9 on the side away from that which is to engage the skin. A central aperture 10 extends through both the film 8 and layer 9, its diameter being slightly less than the external

diameter of the main portion of the tube 1.

In use, the pad 3 is stuck to a finger, for example, and a prick is made through the aperture 10. With the plunger 2 in the withdrawn position as shown in Figure 1, the tapered end 4 of the capillary tube is inserted in the aperture 10 and urged in until its extremity is in contact with the skin around the pin prick. By squeezing or massaging the finger, a

droplets of blood are

produced, and capillary action will draw them up the tube 1 , the vent provided by the hole 5 assisting this action. When the tube 1 is filled to above a mark 11 it can be withdrawn and is then in the condition shown in Figure 2.

The sample is then dispensed, for example on a strip 12 as shown in Figure 3, by pressing the plunger 2. At first, there will simply be an escape of air through the hole 5 . But once this is closed off, the sample will be forced out through the tapered end 4 of the tube until the stop 7 meets the rear end of the tube 1. This will give an accurately measured quantity of blood.

Figure 4 shows an embodiment of the adhesive pad 3 in cross-section, using reference letters corresponding to those employed in Figure 1. More particularly, the dashed lines 13 indicate the flow of blood from the subject's finger 14 into the aperture 10 in the pad, where it collects and is retained in the aperture ready for collection, as indicated at 15. The capillary tube described with reference to Figures 1 to 3 is a preferred but not essential means of collecting the blood. Any convenient portable collecting device having a forward end adapted to enter the pad aperture may be employed.

Moreover, by making the foam or similar layer 9 porous to blood, this layer 9 can itself be used to collect the blood. This is convenient when the subject has to take a blood sample personally and then forward it for analysis, as the entire pad incorporating the stored blood can be carefully stripped off and taken or sent to the

laboratory, where the pad can be squeezed to extract the blood for analysis from it. This is a substantial improvement on present practice, where the subject

endeavours to catch the blood exuding from a pin prick on porous paper.

Claims

Cl a i ms

1. A method of taking a blood sample according to which an apertured adhesive pad is applied to the skin, and the skin is pricked through the aperture in the pad so that the escape of blood is confined to a collecting area formed by the aperture in the pad.

2. A method according to claim 1, in which blood is collected from the aperture in the pad by a blood porous layer of the pad behind the adhesive layer.

3. A method according to claim 1, in which blood is collected from the aperture in the pad by a portable collecting device.

4. A method according to claim 3, in which the portable collecting device is a capillary tube.

5. A method according to claim 3, in which the

engagement of the forward end of the capillary tube in the aperture in the pad is such as to render the tube self- supporting.

6. Apparatus for carrying out the method of claim 2, comprising an adhesive pad having a generally central aperture, an impervious adhesive layer on one face and a thicker layer of blood-porous material behind the adhesive layer.

7. Apparatus for carrying out the method of claim 3, comprising an adhesive pad having a generally central blood-collecting aperture and an adhesive layer on one face, together with a portable collecting device having a forward end adapted to enter the aperture in the pad to withdraw blood therefrom.

8. Apparatus according to claim 7, in which the portable collecting device is a capillary tube.

9. Apparatus according to claim 8, wherein the capillary tube has a tapered forward end.

10. Apparatus according to claim 8 or claim 9, in which the pad aperture and the forward end of the capillary tube are mutually adapted to locate the extremity of the forward end of the tube against the skin.

11. Apparatus according to claim 8 or claim 9 or claim 10, in which the capillary tube has a vent hole at an intermediate point in its length.

12. Apparatus according to claim 11, in which the

capillary tube is associated with a plunger inserted in the rear end of the tube.

13. Apparatus according to claim 12, in which the plunger carries a stop for limiting its forward insertion through the tube.

14. A method of taking a blood sample substantially as hereinbefore described.

15. Apparatus for taking a blood sample substantially as hereinbefore described with reference, to the accompanying drawings.