WO1988002238A1

WO1988002238A1 - Blood sampling device

Info

Publication number: WO1988002238A1
Application number: PCT/GB1987/000684
Authority: WO
Inventors: William Thomas Dennis Bates
Original assignee: William Thomas Dennis Bates
Priority date: 1986-09-30
Filing date: 1987-09-29
Publication date: 1988-04-07
Also published as: GB8623499D0

Abstract

A sampling device comprises a needle unit which includes a barrel (20) and a double-ended needle (21) mounted to the barrel and disposed along the length of the latter with one end projecting outwardly from one end of the barrel, and a sample tube (10) for insertion into the other end of the barrel so that a cap (12) of the tube will be pierced by the other end of the needle and so that, upon continued displacement of the tube (10) into the barrel, said other end of the needle will arrest a plunger (14) within the tube to cause a space (13) within the tube to be increased and apply suction through the needle to its one end.

Description

Blood sampling device.

This invention relates to a device for taking a sample of blood from a patient.

I have now devised a sampling device which is of simple construction and simple to use and which has a number of other advantageous features.

In accordance with this invention, there is provi¬ ded a sampling device comprising a needle unit which in¬ cludes a barrel and a double-ended needle mounted to the barrel and disposed along the length of the latter with one end projecting outwardly from one end of the barrel, and a sample tube for insertion into the other end of the barrel so that a cap of the tube will be pierced by the other end of the needle and so that, upon continued dis¬ placement of the tube into the barrel, said other end of the needle will arrest a plunger within the tube to cause a space within the tube to be increased and apply suction through the needle to its one end.

After a sample has been drawn into the sample tube by the suction created in this manner, the sample tube may be removed from the needle unit, the cap self-sealing as the needle disengages from it. The sample can then be stored in the tube, which is self-compensating against temperature variations because the plunger will displace along the tube to follow expansions and contractions of the sample volume.

Preferably the plunger forms a second part of the cap, these two parts being engaged together initially to define a sealed cavity: this cavity may contain an anti¬ coagulant or other additive. When the tube is first pushed into the barrel of the needle unit, the needle pierces the first part of the cap and then contacts the plunger or second part of the cap; continued displacement of the tube will cause the two cap parts to be pushed apart and the additive within the cavity will dissolve in the blood sample which is subsequently drawn in.

After the sample has been drawn into the tube and had the additive dissolved in it as described above, immed¬ iately the sample may be re-injected back into the patient. For this purpose, a push rod may be inserted into the tube from its outer end and so as to contact the plunger, then used to hold the plunger in position whilst the tube is withdrawn from the barrel to cause the sample to be urged out of t^'he tube and back through the needle into the patient. This gives the device the particular advantage that a sample may be taken, have an additive dissolved in it and then re-injected into the patient without any risk of the user co ing into contact with any of the patient's blood, so that the user avoids any risk of infection in this way. As seen from a second aspect, this invention also provides a needle unit comprising a barrel and a double- ended needle mounted to the barrel along the length of the latter with one end of the needle projecting outwardly from one end of the barrel and the other end of the needle pointing towards the other, open end of the barrel.

As seen from a third aspect, this invention also provides a sample tube closed at one end by a cap which may be pierced by a needle, and a plunger within and dis- placeable along the tube.

Embodiments of this invention will now be described by way of examples only and with reference to the accompany¬ ing drawings, in which: FIGURE 1 is a longitudinal section through a sample tube in accordance with the invention;

FIGURE 2 is a longitudinal section through a samp¬ ling device comprising a needle unit used together with the tube of Figure 1, the tube having just been inserted into a barrel of the needle unit;

FIGURE 3 is a similar view to that of Figure 2 show¬ ing the device when the tube has been pushed further into the barrel of the needle unit; and FIGURE 4 is another similar view showing a push rod in position ready for the device to be used for re-injecting the sample back into the patient.

Referring to Figure 1, there is shown a sample tube which has a cap sealing one of its two open ends, the cap including a sealed cavity: this cavity may contain an anti-coagulant or any other appropriate additive. The tube 10 itself is cylindrical and may-be formed of glass, or plastics. The cap is formed in two parts 12, 14, mould¬ ed of rubber or similar material. The part part 12 com- prises a round top portion 12a. and two depending cylindrical skirt portions 12b_, 12 defining an annular socket between them so that this cap part may be fitted to the top of the tube 10, the skirt portions being received one within and the other around the tube 10 as shown and resiliently bearing against the inside and outside surfaces of the tube to seal the tube. The other part 14 of the cap has a cylindrical plunger portion 15 with spaced annular ribs 15a., 15b_ which are a sliding but sealing fit within the tube 10. The part 14 also has a projecting plug portion 16 which fits into the end of the inner skirt portion 12£ of the cap part 12, so forming a sealed cavity 13 within the cap part 12. In order to enhance the seal to this cavity, the skirt portion 12£ has an internal annular rib 12d_ at its end and the plug portion 16 has an annular rib 16a. at its end, to fit beyond the rib 12d_ when the plug portion is inserted into the free end of the skirt portion 12£. The plug portion 16 is further provided with an insert 17 of hard plastics or similar material at its centre, for a purpose which will be explained. Referring to Figure 2, the sample tube of Figure 1 is shown being used with a needle unit. The latter unit comprises a cylindrical barrel 20 of glass or plastics, which is closed at its bottom end and open at its top end. A double-ended needle 21* is disposed along the axis of the barrel 20, extending through and mounted to the bottom of the barrel. One end of the needle 21 projects from the bottom of the barrel and is formed in the usual manner of a hypodermic needle (i.e. its end is cut at an angle). The other end of the needle extends to close to the top of t-he barrel and is also cut at an angle as shown.

In use, and shown in Figure 2, the sample tube of Figure 1 is inserted cap-first into the open end of the barrel 20 and pushed in so that the needle will pierce the top 12a_ of the cap part 12 and then come to rest against the insert 17 of the cap part 14. Then in order to take a blood sample from a patient, the exterior projecting end of the needle is used to pierce the patient's blood vessel in the usual manner, after which the sample tube 10 is pushed further into the barrel 20: for this purpose, the barrel is provided with opposed wings 22a, 22b_, at its top, for the user to engage the first two fingers of one hand under these wings whilst pressing the tube 10 inwards with the thumb of the same hand applied against the end of this tube. As tube 10 is pushed further into barrel 20, firstly the two cap parts 12, 14 will become disengaged, opening the cavity 13 as shown in Figure 3s then with continued inward movement of the tube 10, suc¬ tion is created within this tube because, with the cap part 14 acting as a plunger relative to the tube, the volume of cavity 13 is effectively increased progressi¬ vely. Thus, as the tube 10 is moved continuously into the barrel, blood is drawn from the patient, through the needle and into the space within tube 10 between its two cap parts 12, 14. Any anti-coagulant or other additive originally sealed within the cavity 13 will now dissolve in the blood sample drawn in.

Conveniently, a stop member 18 (Figure 3) may be fitted into the open end of the sample tube 10 before the latter is inserted into the barrel 20. This stop member 18 will then limit the inward travel of the sample tube 10, by coming into contact with the cap part 14. The stop member used each time can be selected from a number of such members of different lengths, appropriate for drawing in different but predetermined volumes of blood.

After the blood sample has been drawn into the sample tube, the latter is withdrawn from the barrel 20 and, as the needle disengages from the cap part 12, the top of the latter self-seals (being of rubber or similar resilient material). The blood sample can now be stored in the tube 10 and it will be appreciated that tube is self-compensating with respect to temperature variations: thus if the temper¬ ature should rise and the volume of stored blood sample increase, the cap part 14 (serving as a sealed plunger) will be urged towards the open end of tube 10 by the expand¬ ing volume of blood; similarly if the temperature should fall, the cap part 14 will be drawn inwardly along the tube as a consequence of the contraction of the blood sample.

The sampling device shown in Figure 2 to 4 may also be used to take a sample of blood and to dissolve in it the additive contained in the cap cavity 13, and then immed- iately to re-inject the blood sample back into the patient without removing the needle from the patient. Thus, as shown in Figure 4, preferably the tube 10 is formed with opposed wings 10a_, 10b, at its open end: then a push rod 30 may be inserted into this open end of the tube 10 and against the cap part 14 (after the blood has been drawn in) and the user may engage the wings 10a, 10b with the first two fingers of one hand and the outer end of the push rod with the thumb of the same hand. By squeezing the two fingers towards the thumb, the tube 10 is withdrawn from the barrel 20 causing the blood contained in the tube to be urged back down the needle and into the patient's blood¬ stream. The sampling device may then be disposed of with¬ out at any time the user risking coming into contact with any of the patient's blood.

Claims

1. A sampling device comprising a needle unit which includes a barrel and a double-ended needle mounted to the barrel and disposed along the length of the latter with one end projecting outwardly from one end of the barrel, and a sample tube for insertion into the other end of the barrel so that a cap of the tube will be pierced by the other end of the needle and so that, upon continued displacement of the tube into the barrel, said other end of the needle will arrest a plunger within the tube to cause a space within the tube to be increased and apply suction through the needle to its one end.

2. A sampling device as claimed in claim 1, in which the plunger forms a second part of the cap, these two parts being engaged together initially to define a sealed cavity and arranged so that when the tube is first pushed into the barrel of the needle unit, the needle pierces the first part of the cap and then contacts the plunger or second part of the cap and continued displacement of the tube causes the two cap parts to be pushed apart.

3. A sampling device as claimed in claim 2, compris¬ ing a push rod which may be inserted into the tube from its outer end and so as to contact the plunger, then used to hold the plunger in position whilst the tube is with¬ drawn from the barrel to cause a sample to be urged out of the tube and out through the needle.

4. A needle unit comprising a barrel and a double- ended needle mounted to the barrel along the length of the latter with one end of the needle projecting outwardly from one end of the barrel and the other end of the needle pointing towards the other, open end of the barrel.

5. A sample tube closed at one end by a cap which may be pierced by a needle, and a plunger within and dis- placeable along the tube.