Blood collecting needle

Abstract: A blood collecting needle of the present invention comprises a hollow cannula (41) both ends of which are sharp tips, and a hub (10) for supporting the center portion thereof. The hub comprises a sheath (50) which surrounds the cannula in a liquid sealed state projecting from the back section of the hub, formed of an elastic body fixedly mounted on the hub, and an air passage (19) connecting the space between the sheath and the cannula with outside air. As a result, flashback can be reliably confirmed, for example, when the tip of the cannula pierces an intravenous vein.

Description: The present invention relates to a blood collecting needle, and more particularly, to a blood collecting needle which is capable of making one or more blood collections after a being for blood collection is connected to a storage chamber which has previously been placed at a negative pressure. In the prior art, blood collecting units by which a plurality of blood collections are made possible with one piercing are frequently used when performing clinical tests. These units, for example, as shown in Fig. 5, comprise cannulas 120 and 130 disposed at both ends of a hub 110, a blood collecting needle 100 having an elastic sheath 135 mounted so as to surround the cannula 130, a cylindrical holder 200 in which the blood collecting needle 100 is fixedly mounted, and a blood collecting tube 300 which is inserted into this holder 200 and placed at a negative pressure (evacuated pressure) beforehand. A rubber or a gass-barrier stopper is inserted into the blood collecting tube 300 so that the inside thereof is maintained at a negative pressure. When collecting blood, first a holder 200 and a blood collecting needle 100 are assembled into one piece. A cannula 120 is made to pierce a vein and the vein is secured. The blood collecting tube 300 is pushed into the holder, and the cannula 130 is caused to pass through the elastic sheath 135 and the rubber stopper 310. As a result, blood collection is started and completed in a state in which the pressure inside the blood collecting tube 300 is balanced with the intravenous pressure. However, in such a conventional vacuum blood collecting system, it is impossible to confirm a so-called flashback, since there is no place where any gas inside the cannula or the elastic sheath can escape when a vein is pierced and before the blood collecting tube 300 is pushed into the holder. For this reason, there is a danger that blood collection will sometimes start when the cannula pierces at a position other than the vein. To solve such a problem, a needle assembly equipped with a mechanism capable of confirming this flashback is proposed Japanese Patent Publication for Opposition (KOKOKU) No. 2-21809 (Priority of United States Patent Application Serial No. 645 893, filed on August 31, 1984). However, the needle assembly proposed therein is very complex in construction, as it comprises a venting apparatus as a communicating path disposed inside the hub, ring-like compressed sleeves which are inserted into a communicating path disposed inside the apparatus and has drawbacks, such as swelling due to water content, etc. This presents a problem in that it cannot be mass-produced inexpensively. GB-A-1 345 979 describes a blood collecting device comprising a cannula having sharp ends, a holder for said cannula, an air vent and a valve surrounding one end of the cannula. In the needle of the prior art, a negative pressure is applied to sleeves housed inside the housing at the time blood is collected. The needle cannot be fully sealed from the outside, lacks adequate safety precautions, and has a lot of dead volume. SUMMARY OF THE INVENTION The present invention has been devised to solve the above-mentioned problems of the prior art. An object of the present invention is to provide a blood collecting needle having a very simple construction and a mechanism capable of reliably confirming flashback. To this end, according to the present invention, there is provided a blood collecting needle, comprising: a hollow cannula, both ends of which are sharp tips; and a hub for supporting substantially the center portion thereof, wherein the hub further comprises a sheath which surrounds the cannula in a liquid sealed state projecting from the back section of the hub, formed of an elastic body fixedly mounted on the hub, and an air passage connecting the space between the sheath and the cannula with outside air. In addition, another object of the present invention is to provide a blood collecting needle in which impurities from the outside will not enter, and the blood specimen inside will not leak outside. To this end, according to the present invention, there is provided a blood collecting needle comprising a substantially cylindrical hub; a cannula extending from both ends of the hub in an axial direction and having sharp tips whose internal path is continuous; and a cylindrical elastic sheath with a bottom, fitted into the hub in a liquid sealed state in such a manner as to surround one of the extending ends of the cannula, wherein the hub comprises an axial communicating passage into which the cannula is inserted and fixed, an air passage connecting the internal cavity of the cylindrical elastic sheath having a bottom with the outside atmosphere, and a permeable filter, fixedly mounted on the outside mouth section of the air passage, having a small hole for permitting gases but not liquids to pass. Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially sectional view of a blood collecting needle according to a first embodiment of the present invention; Fig. 2 is a partially sectional view of a blood collecting needle according to a second embodiment of the present invention; Fig. 3 is a schematic view showing an operation of a blood collecting needle of the present invention; Fig. 4 is a cross-sectional view showing a state during blood collection; Fig. 5 is an exploded perspective view of a blood collection unit; Fig. 6 is a partially sectional view of a blood collecting needle according to a third embodiment of the present invention; Fig. 7 is a front view of the blood collecting needle according to the third embodiment ; Fig. 8 is a partially sectional view of a blood collecting needle according to a fourth embodiment of the present invention; and Fig. 9 is a magnified section around the filter of the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a blood collecting needle of the present invention will now be explained with reference to Fig. 1. As shown in Fig. 1, a blood collecting needle 1 of the present invention comprises a substantially cylindrical hub 10, cannulas 41 and 45 extending from both ends of the hub 10 in an axial direction and having sharp tips whose internal path is continuous, and a cylindrical elastic sheath 50 having a bottom fitted into the hub 10 in a liquid sealed state in such a manner as to surround one of the extending ends of the cannula 45. The hub 10 is formed in a substantially cylindrical shape. Disposed in the inside thereof are a communicating cavity 13 which is positioned through the center in an axial direction thereof and an air passage 19 connecting the internal cavity section E of the cylindrical elastic sheath 50 having a bottom with the outside atmosphere. The communicating passage 13 is a hole into which cannulas 41 and 45 are inserted and fixed. The inner diameter thereof is slightly larger than the outer diameter of the cannulas 41 and 45. Usually, the difference between them is approximately 0 to 0.3 mm. In the air passage 19, an end 19a thereof is positioned at a back end of the hub 10 and disposed in such a manner as to connect with the internal cavity E of the elastic sheath 50. The other end 19b of the air passage 19 is disposed, for example, on the outer surface of the trunk section of the hub 10 so as to communicate with the outside atmosphere. In this embodiment, the air passage 19 is shaped in the letter L in such a way that it is axially bored a predetermined length from the one end 19a spaced by a given partition wall 21 from the axial communicating passage 13, and then the direction of the passage 19 is changed toward the outer surface and bored to the outside. Although, in this embodiment, the cross section of the air passage 19 is shaped in a circle, it is not limited to this shape, but various shapes may be used. The diameter of the air passage 19 is approximately 0.2 to 2 mm. An air permeable filter 7 is fused by ultra-sonic fusion, thermal fusion or the like on the other end 19b of such an air passage 19, such other end 19b connecting with the outside atmosphere. This air permeable filter 7 has a small passage for permitting gases but not liquids to pass. This filter should preferably have a water repellent property. In this embodiment, fluorine type resin, such as teflon, or olefin type resin, such as PP, PE or the like, is contained therein. Further, in the hub 10, a screw section 15 is provided on the outer surface in the center portion of the trunk section of the main body thereof. The mouth section of the holder 200 (see Figs. 3 and 4), which is equal to one blood collection unit, is screwed to the screw section 15. Furthermore, a locking section 17 for locking the elastic sheath 50 is formed in the back end of the hub 10. The shape of the locking section 17 is not particularly limited, but preferably is shaped in such a way that the elastic sheath 50 cannot be easily released. In this embodiment, as an example, the locking section 17 has a locking projection 17a projecting in the form of a jaw. The elastic sheath 50 locked to such an engagement section is cylindrically shaped and has a bottom section 51. It has an internal cavity section E serving as a space surrounding one extending end of the cannulas 45. It is required that this elastic sheath 50 have a proper elasticity such that the elastic sheath 50 can be sealed again after it is pierced temporarily by the cannula 45 during blood collection. As materials to be used, synthetic rubber, elastomer, etc. can be employed. In particular, materials having transparent or semi-transparent characteristics should preferably be used so as to confirm a flashback phenomenon such that blood is jetted out when the cannula 41 is made to pierce a vein. The dimensions of such an elastic sheath are usually approximately 10 to 30 mm in length with an outer diameter of 1 to 3 mm. When a specimen is being collected, the sharp tips of the cannulas 41 and 45 inserted into the communicating passage 13 of the hub 10 are respectively made to pierce one specimen source, such as blood inside a vein, or a specimen storage chamber, such as a so-called vacuum or negative-pressure blood collection tube or the like. The cannulas 41 and 45 may be separate bodies, or may be continuous and made into one piece. Such cannulas 41 and 45 are fixedly mounted by various kinds of bonding agents in a state in which they are inserted into the communicating passage 13. The hub 10 is usually formed by injection molding. To make flashback easily confirmed, transparent or semi-transparent materials are preferable. To be specific, the following can be employed: polypropylene, polyethlene, polystyrene, polyethlene terephthalate, polymethyl pentene, polycarbonate, polyacrylonitrile, resin materials of ABS, etc. The dimensions of the hub 10 are approximately 10 to 30 mm in length with an outer diameter of 5 to 15 mm. With the above construction, for example, when the cannula 41 is made to pierce a vein, a flashback phenomenon can be confirmed since the pressure of the internal cavity section E of the elastic sheath 50 is lower than a blood pressure value inside the vein. In other words, when the cannula 41 is not made to correctly pierce a vein, the flashback phenomenon does not occur. Therefore, a wasteful operation of collecting blood need not be performed. Next, a second embodiment of a blood collecting needle of the invention will be explained with reference to Fig. 2. A point of fundamental difference between a blood collecting needle 2 of the second embodiment and that of the first embodiment is the construction of an air passage disposed inside the hub. That is, as regards an air passage 69 of the second embodiment, portions thereof, in particular, portions oriented in an axial direction, are formed to be in contact with an axial communicating passage 63. As a consequence, a part of the outer surface of a cannula constitutes a part of the air passage 69 when the cannula is inserted into the communicating passage 63. With such a construction, it is possible to make small the outer diameter of the locking section 67 for locking the elastic sheath 50, and a communicating passage can be easily formed by injection molding. A third embodiment of a blood collecting needle will be explained with reference to figs. 6 and 7. Fig 7 is a front view of the blood collecting needle of the present embodiment. As shown in Fig. 7, four holes 39 are provided on the hub 10 around the axis of the cannula 41. Fig 6 is a partially sectional view of the blood collecting needle of the present third embodiment. As shown, the hub 10 of the present third embodiment comprises of two members 10a,10b. The members 10a,10b and filter 7 are fixed to each other by ultra-sonic fusion, thermal fusion or other well known skill. According to the third embodiment, the hub 10 is manufactured easily and it is possible to reduce the cost for the manufacture. A fourth embodiment of the blood collecting needle will be explained with reference to Figs. 8 and 9. According to above described embodiments, it is possible to confirm the flashback. However, there is a fear that the blood leaks from the filter 7 by the cause high pressure against the filter 7 if the air in the hub 10 was very little. To secure air in the hub 10, the present fourth embodiment provides the structure of the needle as shown Fig. 8. The difference between the present embodiment and the above described embodiments is to provide the air chamber in the neighborhood of the outer portion of the air passage 19 which is contacted by the filter 7 as shown in Fig. 8. It is noted that four holes 39 are provided on the hub 10b around the cannula 41 in the same manner as the third embodiment. Fig 9 shows a magnified section view around the filter 7. In the fourth embodiment, the filter 7 is reinforced by the reinforcement member 80 which prevents the filter 7 from bending. In this embodiment, the blood that flows in the air passage 19 does not enter into the air chamber 82 but flows through the filter 7 and reinforcement member 80 When the blood passed through the filter 7 and reinforcement member 80, the filter 7 becomes wet, air flow through the filter 7 is prevented, thus much of air remains in the air chamber 82. The air in the air chamber 82 acts as a cushion and prevents blood from leaking through the filter 7. The end of portion 81a of the chamber wall 81 is tapered in such a manner that it is closer to the filter 7 than the opposite edge. The tapering is to facilitate damp throughout of the filter 7. In the Fig. 9, the radius r 1 of the air chamber 82 is made to be substantially equal to the radius r 0 of the hole 39. However, it is preferable to structure the device so that the radius r 1 is greater than the radius r 0 . If r 1 is less than r 0 , the blood has a tendency to flow into the air chamber 82, thus making the volume of air chamber 82 smaller. As explained above, according to the present embodiment, because air can be retained in the hub 10, blood will not leak through the filter 7. The filter 7 of embodiments 1 to 4 is made from porous material which has many micro-holes. The micro-hole is preferably between 0.2µm and 10µm. In the embodiments, the polytetrafluoroethylene which has micro holes of 1µm to 3µm diameter is used. Also, the thickness of the filter 7 is preferably between 0.05mm and 0.5mm, determined by the air flow resistance. In the present embodiments, a thickness between 0.07mm to 0.16mm is used. The reinforcement member 80 is formed of a hydrophilic member of the sureface fo the member which is hydrophilic-treated. For example, a sureface of which polyester (200 mesh ) is plasma-treated is use for the reinforcement member 80. Next, an explanation will be provided of the operation of the above-described first to fourth blood collecting needles. As shown in Fig. 3, a mouth section of the holder 200 is screwed to the screw section 15 provided on the outer surface of the hub 10 of the blood collecting needle 1, and the blood collecting needle and the holder 200 are made into one piece. In this state, the first cannula 41, which is a blood collecting needle, is made to pierce a blood vessel V. Thereupon, the blood inside the blood vessel V flows into the internal cavity section E of an elastic sheath after passing from the internal passage of the cannula 41 to the internal passage of the cannula 45. The blood further rises to the inside of the air passage and stops at the air permeable filter 7. As the result of at least one of either the hub 10 or the elastic sheath 50 being formed of a transparent or semi-transparent material, flashback can be confirmed easily. When this flashback is confirmed, since at least the tip of the cannula 41 is positioned inside an object vein, the blood collecting tube 300 is pushed thereinto from the opening of the back end of the holder 200. This state is shown in Fig. 4. As a result, the cannula 45 passes through the elastic sheath 50 and the rubber stopper of the blood collecting tube 300, and the tip thereof reaches the inside of the blood vessel to be collected. Since the pressure inside the blood collecting tube 300 is fully smaller than the blood pressure in the vein, the blood continues to flow thereinto until the difference between these pressures reaches a predetermined value. When the inventor of the present invention made an experiment for confirming flashback, flashback was confirmed even under an intravenous pressure as low as approximately 5 cmaq. That is, the blood collecting needle of the present invention has an advantage in that it is capable of reliably confirming flashback with a very simple construction. As has been explained above, according to the first invention, it is possible to provide a blood collecting needle having a very simple construction and capable of reliably confirming flashback. According to the second invention, it is possible to provide a blood collecting needle in which impurities from the outside will not enter, and the blood specimen inside will not leak outside.

Claims: A blood collecting needle, comprising : a hollow cannula (41), both ends of which are sharp tips ; and a hub (10) for holding a substantially central portion of the cannula, wherein said hub is formed of a transparent or semi-transparent material, and comprises : a sheath (50) which surrounds the cannula in a liquid sealed state projecting from the back section of the hub formed of an elastic body fixedly mounted on the hub , and a holder mounting portion (15) for mounting a holder (200) which is a guide of the insertion of a blood collecting tube (300), characterized in that said hub (10) further comprises : an air passage (19,69) connecting the space within the sheath surrounding the cannula with the air outside of the hub, having an exit provided at a position on the outer surface of the hub, which, when the holder is mounted on the holder mounting portion, is outside of the holder; and a permeable filter (7), placed on the air passage end connecting with the outside atmosphere, capable of permitting gases but not liquids to pass therethrough. A blood collecting needle according to claim 1, wherein the sheath (50) is an elastic sheath formed of a transparent or semi-transparent material. A blood collecting needle according to claim 1, wherein the permeable filter(7) contains fluorine-type resin or olefin-type resin. A blood collecting needle according to any one of claims 1 to 3, wherein a part of the air passage is formed in parallel in such a manner as to be in contact with the outer surface of the cannula (41). A blood collecting needle according to any one of claims 1 to 3, wherein the air passage (69) is formed with a given partition wall being spaced from the axial communication passage. A blood collecting needle according to any one of claims 1 to 3, wherein the hub (10) further comprises an air room (82) having one opening which connects to a portion of the air passage (19).

Inventors: KUROSE KATSUTOSHI, KUROSE, KATSUTOSHI, Kurose, Katsutoshi, c/o Terumo K.K.
Applicants: TERUMO CORP, TERUMO KABUSHIKI KAISHA
Application year: 1991
Main classification: A61B5
IPC codes: A61B5