MEDICAL TOOL INTRODUCTION CANNULA AND METHOD OF MANUFACTURING THE SAME

Abstract: Medical instrument introduction cannula, which is useful as a guide means for introducing and indwelling a rod-like medical instrument such as a catheter and a guide wire. This cannula is removed after use from the medical instrument by being splitted. This cannula is formed of a hollow tubular body (11) having a strip member (13) consisting of a material different from the other portion of the tubular body (11), which extends over the entire or almost the entire length of the tubular body (11). The strip member (13) has a weld line (14) along the length of the strip member, or consists of a resin which exhibits a good bonding property only to one of the other components forming the tubular body. The tubular body (11) can be splitted by way of the weld line (14) or the removal of the strip member having such a bonding property. The method of manufacturing the medical instrument intruduction cannular by a two-color extruder is also disclosed.

Description: The present invention relates to a synthetic resin introduction cannula used for introducing and indwelling a rod-like medical tool such as a catheter, a guide wire, or the like in a blood vessel, and a method of manufacturing the same. Conventionally, when a catheter is introduced and indwelled in a blood vessel, a flexible introduction cannula of a synthetic resin is used. More specifically, an introduction cannula is fitted on an inner cannula of a syringe so that the distal end of the inner cannula projects therefrom. The inner cannula is then pierced into a blood vessel until the distal end of the introduction cannula is inserted in the blood vessel. Then, the inner cannula is removed from the blood vessel while the introduction cannula is left in position. In this manner, a desired catheter is inserted in the introduction cannula while the introduction cannula is left in the blood vessel, and the distal end portion of the catheter is then inserted in the blood vessel. After the catheter is indwelled at a predetermined position in the blood vessel, the unnecessary introduction cannula is removed from the blood vessel. Preferably, the introduction cannula is also removed from the catheter. It is undesirable for sanitary reasons that the introduction cannula is left in the body after being removed from the blood vessel. In addition, the introduction cannula in this state disturbs the subsequent operations. However, it is impossible to pull out the introduction cannula from the catheter since an extended portion such a connector of the catheter is present. For this reason, some proposals for removing the used introduction cannula from the catheter have been made. For example, in one proposal, a slit is preformed in the longitudinal direction of the introduction cannula, and the introduction cannula is removed from the catheter through the slit. In Japanese Patent Disclosure (Kokai) No. 56-11069, a pair of linear members of a single plastic material different from that of the remaining portion are formed in opposing portions in the radial direction of an introduction tube. The base portion of an introduction cannula is coupled to a fitting portion with an inner cannula hub with a slit, which is coupled to the linear members. The used introduction cannula is torn at the linear members to be split into two portions while gripping the fitting portion. However, in the former method, the mechanical strength of the introduction cannula is decreased, resulting in poor operability. In addition, when a cannula is introduced into a blood vessel, blood may leak from the slit. In the latter method, the linear members are easily cracked upon post-machining, e.g., cutting, distal end machining, and the like of the introduction cannula or handling as a product. An introduction cannula with cracked linear members cannot be used, and, if used, blood leakage may occur. The same applies to the corresponding catheter known from EP-A-0 021 446 disclosing all the features of the preambles of Claims 1 and 12. In the introduction cannula having linear members for splitting the introduction cannula as described above, since the color of the strip members resembles that of the introduction cannula body, it is difficult to immediately confirm the positions of the strip members when they are removed from the introduction cannula body, resulting in cumbersome splitting operation of the introduction cannula. The present invention has been made in consideration of the above situation and has as its object to provide a medical tool introduction cannula which can be free from inadvertent peeling or splitting upon post-machining or during handling as a product, and can be easily split and removed from a catheter or the like after it is used, and a method of manufacturing the same. According to the present invention, as a first means for achieving the above object, there is provided a medical tool introduction cannula as defined by the features of Claim 1. The distal end of the tubular body is preferably tapered thinner to be in tight contact with an inner cannula inserted therethrough, and its base portion is preferably tapered thicker. The main portion of the hollow tubular body is preferably formed of a thermoplastic material, such as polypropylene (PP), high-densiy polyethylene, semi-hard polyvinyl chloride, fluoro plastics, or the like. It is also preferable that the main portion of the hollow tubular body has a some degree of flexibility that is sufficient to allow a catheter to be introduced thereinto, as the hollow tubular body is being inserted in a human body, and to allow the hollow tubular body to be removed from the cather introduced therein. The strip member is preferably formed of a thermoplastic material such as a blend polymer of EVA and PP, a blend polymer of polyethylene and EVA, or the like. According to the present invention, as another means for solving the above problem, there is provided a method of manufacturing the medical tool introduction cannula as defined by the features of Claim 8. The buffer plate is preferably arranged at a position separated from the edge portion of the die outlet port by 0 to 5 mm, and preferably has a height 1/2 or more of that of the resin flow path of the die. Note that a melted resin flow is once divided in a cylinder, and the divided flows are joined and coupled again. In this specification, the weld line means a portion where fusion bonding of the coupled portion is incomplete, and a mechanical strength is decreased. Furthermore, according to an embodiment of the present invention, in the medical tool introduction cannula according to the first means (or feature), the strip member to be split or peeled is formed to have a color quite different from that of the remaining portion of the hollow tubular body. The phrase "the strip member is formed to have a color quite different from that of the remaining portion of the hollow tubular body" means that only the strip member or only the remaining portion of the hollow tubular body is colored by a coloring agent or both are colored to have a noticeable color difference. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of the medical tool introduction cannula according to the first feature of the present invention; Fig. 2 is a sectional view taken along the line II-II of Fig. 1; Fig. 3 is a sectional view showing the medical tool introduction cannula which is torn apart; Fig. 4 is a front view of a manufacturing apparatus of the medical tool introuduction cannula of Fig. 1; Fig. 5 is a sectional view of the manufacturing apparatus of Fig. 4; Fig. 6 is a front view of another manufacturing apparatus of the medical tool introuduction cannula; Fig. 7 is a sectional view of the manufacturing apparatus of Fig. 6; Fig. 8 to 10 are schematical view explaining the operation of the medical tool introduction cannula; The present invention according to the first means will be described with reference to Figs. 1 to 5. Fig. 1 is a perspective view of medical tool introduction cannula 11 according to the present invention. Introduction cannula 11 comprises a hollow tubular body having two open ends through which a rod-like medical tool such as a catheter can be inserted. Cannula 11 has a cylindrical shape in which central portion 11 has a size of, e.g., 12G to 16G, distal end portion 11b is tapered thinner to be in tight contact with an inner cannula (not shown), and base portion 11c is tapered thicker. As shown in Figs. 1 and 2, strip member 13 is formed in a specific portion along the circumferential direction of the tubular body to extend over the entire length in the longitudinal direction of the tubular body. Strip member 13 has physical properties different from main portion 12. Weld line 14 is formed at a substantially intermediate portion in the widthwise direction of strip member 13 to extend in the longitudinal direction. Main portion 12 preferably consists of a relatively hard synthetic resin material in view of operability of introduction cannula 11 as a whole. Examples of the synthetic resin are polypropylene, high-density polyethylene, semi-hard polyvinyl chloride, poly-4-methylpentene-1, and polycarbonate. Strip member 13 can consist of a soft thermoplastic resin material having good compatibility with main portion 12. Examples of the thermoplastic resin include appropriate blend polymers such as a polypropylene/ethylene-vinyl acetate copolymer, a high-density polyethylene/ethylene-vinyl acetate copolymer, polypropylene/polyethylene, a methylpentene polymer/ethylene-vinyl acetate copolymer, methylpentene polymer/polyethylene, and the like. If the main portion and the strip member are formed of materials having extremely different properties in terms of compatibility, they easily crack at their boundary, and post-machining is rendered very difficult. Strip member 13 need not always be formed over the entire length of the tubular body as shown in Fig. 1. For example, strip member 13 may be omitted at the distal end portion to increase the mechanical strength of this portion. In addition, weld line 14 may be omitted in the distal end portion of the tubular body to increase the tear strength at the distal end portion of the tubular body. The width of strip member 13 is not particularly limited, but is preferably set to be 1/2 or less the circumference of the tubular body. Two or more strip members 13 may be formed as needed. Weld line 14 can be formed by using two-color extruder 15 having two cylinders 15a and 15b as shown in Figs. 4 and 5. In extruder 15, buffer plate 18 projects from the inner surface of inner mold 19 near an outlet portion of die 17. Buffer plate 18 has a thickness (e.g., 1 mm or less) large enough to interrupt a resin flow from cylinder 15a for molding strip member 13 at an intermediate portion of its width. Therefore, the resin flow forming strip member 13 is divided when it passes buffer plate 18, and thereafter, the divided flows are joined again. As a result, weld line 14 can be formed in a final product. The position, height, and the like of buffer plate 18 can be appropriately determined in association with a blend of synthetic resins used. Normally, distance L between the distal end position of buffer plate 18 and the distal end of die 17 is set to be 0 to 5 mm, and a ratio of distance h between the upper end of buffer plate 18 and the inner wall of outer mold 20 to interval H of resin path 21 is set to be h : H = 0 to 1/2 : 1 and preferably, 0 to 1/5 : 1. In this case, weld line 14 having a desired tear strength can be obtained. Since a coupling force at weld line 14 between two side portions is considerably smaller than that of the synthetic resin at the remaining circumferential portion, weld line 14 can be broken by applying an external stress, and can be easily torn, as shown in Fig. 3 to be separated from catheter 5. The tear strength of weld line 14 can be adjusted by adjusting the position, height, width (length, thickness), and the like of buffer plate 18, or by adjusting types of resins or a blend of two or more resins constituting strip member 13. One forming method of weld line 14 using the extruder in which buffer plate 18 projects from the inner mold, as shown in Figs. 4 and 5, has been exemplified. However, the present invention is not limited to this, and other arbitrary molding means may be adopted. For example, as shown in Figs. 6 and 7, the same buffer plate 18 as in Figs. 4 and 5 may be provided to an outer mold of die 17 (the same reference numerals denote the same parts as in Figs. 4 and 5). Although not shown, the same buffer plates may be provided to two or more portions of the outer or inner mold, or may be provided to both the outer and inner molds to oppose each other. In either case, the position (L), height (h), size, and the like of the buffer plate can be adjusted and selected in the same manner as in Figs. 4 and 5. A method of using the medical tool introduction cannula of the present invention will be described hereinafter. First, introduction cannula 11 is inserted in syringe 2 shown in Fig. 8, and is pierced into blood vessel 4 or the like together with inner cannula 3 of the syringe. Thereafter, as shown in Fig. 9, inner cannula 3 is pulled out to leave introduction cannula 11 in blood vessel 4. As shown in Fig. 10, catheter 5 is then inserted in introduction cannula 11, and is introduced into blood vessel 4. When used introduction cannula 11 is removed from catheter 5, the proximal end portion of weld line 14 is cut by applying an external stress to introduction cannula 11, as shown in Fig. 3, and weld line 14 is then torn through the proximal end portion. Thus, introduction cannula 11 can be easily removed from catheter 5. In this embodiment, a catheter is introduced using the medical tool introduction cannula. The present invention is not limited to the catheter but may be applied when various other rod-like medical tools are introduced in a human body. Example 1 A pair of buffer plates each having a length of 22 mm and a width of 0.5 mm were provided to an outer mold of a die of a two-color extruder to be in contact with the inner wall of an inner mold, so that their distal ends opposed a die outlet port at an interval of 0.5 mm (i.e., in Fig. 7, "L" = 0.5 mm). Polypropylene (MA-6 (tradename); available from Mitsubishi Petrochemical Co., Ltd.) was flowed into cylinder 15b for forming the main portion of a tubular body, and a mixture of polypropylene (PP) and an ethylene-vinyl acetate copolymer (EVA) (V-401S (tradename); available from Mitsubishi Petrochemical Co., Ltd.) (mixing ratio, PP : EVA = 80 to 90 : 20 to 10) was flowed into cylinder 15a for forming a strip member. At the same time, a takeup speed of a molded product was changed in two steps, thereby obtaining a continuous body of a catheter introduction cannula which had central and base portions of different sizes and complied with a 16G inner cannula. The continuous body was cut into predetermined pieces, and the distal end of each piece was machined. In this case, no cracking of the distal end portions occurred. When the introduction cannula of this example was pierced into a mongrel's blood vessel together with an inner cannula, neither burr nor crack of the distal end portion were observed. In addition, when the introduction cannula was split upon removal, it could be easily split. A catheter introduction cannula was molded following the same procedures as in this example except that SPN-3575 (a product of Dai Nihon Inc Kagaku Kogyo Co. Ltd. Japan) was mixed as a coloring agent in the PP/EVA mixture. As a result, a blue strip member could be obtained.

Claims: A medical tool introduction cannula (11) for introducing a rod-like medical tool into a living body, said introduction cannula (11) comprises a hollow tubular body (11) of a synthetic resin capable of inserting said rod-like medical tool therethrough, at least one portion of said hollow tubular body (11) is formed by a strip member (13) of a material different from the other portion of said hollow tubular body (11) characterized in that said strip member (13) extends over the entire length of said tubular body (11) or over the entire length excluding a distal end portion (11b), and in that it further comprises a weld line (14) which is bonded with a relatively weak force and which is longitudinally formed in said strip member (13). An introduction cannula according to claim 1, characterized in that the distal end of said tubular body (11) is machined to be in tight contact with an inner cannula (3) inserted therethrough, and a base portion (11c) thereof has an extended shape. An introduction cannula according to claim 1, characterized in that a pair of said strip members (13) are arranged to radially oppose each other. An introduction cannula according to claim 1, characterized in that said strip member (13) is colored. An introduction cannula according to claim 1, characterized in that the other portion of said hollow tubular body (11) is colored. An introduction cannula according to claim 1, characterized in that said strip member (13) and the other portion of said hollow tubular body (11) are colored in different colors. An introduction cannula according to claim 1, characterized in that a main portion of said hollow tubular body (11) is formed of a material selected from the group consisting of polypropylene, polyethylene, and poly-4-methyl-pentene-1, and said strip member is formed of a material selected from the group consisting of a polypropylene/ethylenevinyl acetate copolymer, polypropylene/polyethylene, a polyethylene/ethylene-vinyl acetate copolymer, a methylpentene polymer/ethylene-vinyl acetate copolymer, and methylpentene polymer/polyethylene. A method of manufacturing a medical tool introduction cannula for introducing a rod-like medical tool into a living body, said introduction cannula comprises a hollow tubular body (11) capable of inserting said rod-like medical tool therethrough, at least one portion of said hollow tubular body (11) is formed by a strip member (13) of a material different from the other portion of said hollow tubular body (11) to extend over the entire length of said tubular body (11) or over the entire length excluding a distal end portion (11b), and a weld line (14) which is bonded with a relatively weak force is longitudinally formed in said strip member (13), characterized in that molding resin flows of two different materials for forming the medical tool introduction cannula are extruded by an extruder (15) having two cylinders (15a, 15b), one for each of the two different materials, the resin flow from cylinder (15a) for molding the strip member (13) is divided by at least one buffer plate (18) which is disposed near a die outlet port (21) of a molding resin flow path of the extruder, the divided resin flow from cylinder (15a) is subsequently joined and the joined flow is extruded from said die outlet port (21) to mold said introduction cannula. A method according to claim 8, characterized in that said buffer plate (18) is positioned so that a distal end thereof is separated from an edge portion of the die outlet port (21) by 0 to 5 mm. A method according to claim 9, characterized in that a height of said buffer plate (18) is set to be not less than 1/2 that of the resin flow path of the die. A method according to claim 9, characterized in that the molding resin flows are initially one integral resin flow before divided by the buffer plate (18). A medical instrument assembly comprising: (a) a medical tool introduction cannula (11) for introducing a rod-like medical tool into a living body, said introduction cannula (11) comprises a hollow tubular body (11) of a synthetic resin capable of inserting said rod-like medical tool therethrough, at least one portion of said hollow tubular body (11) is formed by a strip member (13) of a material different from the other portion of said hollow tubular body (11), characterized in that said strip member (13) extends over the entire length of said tubular body (11) or over the entire length excluding a distal end portion (11b), and in that it further comprises a weld line (14) which is bonded with a relatively weak force and which is longitudinally formed in said strip member (13); and (b) a syringe (2) fitted with an inner cannula, and detachably inserted into the medical tool introduction cannula (11) such that a distal end of the inner cannula is projected from a tip end of the medical tool introduction cannula.

Inventors: ISHIDA, TOSHINOBU, KOUSAI, TADASHI, MORIUCHI, YOUSUKE
Applicants: TERUMO KABUSHIKI KAISHA
Application year: 1988
Main classification: A61M25
IPC codes: A61M25, B29C47