METHOD OF PRODUCTION OF MULTI-LUMINAL CATHETER AND MULTI-LUMINAL CATHETER ASSEMBLY

Abstract: A multi-luminal catheter of this invention is characterized in that the cross-sectional shape of each lumen at a connection portion for an extension tube is molded in advance to the outer shape of the extension tube to be connected. Accordingly, smooth and hermetic connection between a catheter body and the extension tube, that has not been accomplished in the past, can be obtained, and the formation of steps of the lumen which increases fluid resistance can be prevented. This multi-luminal catheter can be produced by pressing a core metal having substantially the same shape as that of the outer shape of the extension tube into each lumen of the catheter body at the connection portion for the extension tube and inserting the core metal into a molding die while heating it. Higher air-tightness and connection strength can be obtained by fitting the connection end of the extension tube into each lumen at the connection portion of the multi-luminal catheter and integrating them by use of a fixing member.

Description: This invention concerns a method for manufacturing a multi-luminal catheter wherein the lumens of the catheter, which have a different shape to the external form of the extension tubes to be connected to them, are given a shape which corresponds to said external form of said extension tubes at the extension tubes connectors. Further, this invention concerns a method for manufacturing a multi-luminal catheter assembly comprising a catheter body with multiple lumen, extension tubes connected to said catheter and members for fastening the catheter body and the extension tubes together. CA-1 219 785 discloses a method for manufacturing a double lumen catheter which comprises providing a tubular body having two lumens, placing a sleeve on one end of the tubular body and heat shrinking the sleeve in position, introducing heated mandrels having generally conicaly shaped ends in the lumens at the end of the tubular body surrounded by the sleeve so that the tubular body and the sleeve conform to the conical ends of the mandrels, and after a predetermined time removing the mandrels from the Y-shaped portion formed. In order to make most effective use of the volume of the cavities in a multi-luminal catheter, their cross-section is generally not circular, as shown in Fig. 1(b). The cross-sections of the extension tubes to be connected to the catheter body of the other hand are circular, and if these tubes are connected to the catheter without modification, airtight connections are consequently not obtained. Further, even when the cross-sections of both the catheter lumen and extension tubes are circular, the diameters of the extension tube lumens must necessarily be made smaller to insert the tubes into the catheter lumens. For this reason, a differential arises between the lumens, and gives rise to problems such as increased fluid resistance. Conventionally, this problem was solved by making the connection through molded pieces of the same shape as the lumens, or by filling the spaces between the catheter lumens and the outer circumference of the extension tubes with adhesive. If connections were made through molded pieces of the same shape as the catheter lumens, however, the manufacturing cost increased undesirably. If on the other hand the spaces between the inner surfaces of the catheter lumens and extension tubes were filled with adhesive, it was still difficult to obtain a perfectly airtight seal. Further, in multi-luminal catheters manufactured by the above methods, the joint strength between the catheter body and the extension tubes is inadequate, and the tubes easily fall out of the catheter body in actual use. This invention therefore aims to provide a method for manufacturing a multi-luminal catheter wherein extension tubes can be connected easily to the catheter body, and good air-tightness is obtained. The multi-luminal catheter made by the method of this invention is characterized in that it has lumens of substantially the same shape as the ends of the extension tubes to be connected to the tube connectors of the catheter body, which consists of thermoplastic resin and has multiple lumens of different shape to the external form of said tubes. As the shapes of the lumens at the extension tube connectors in this multi-luminal catheter, are substantially identical to the external form of said tubes, the tube connections can be made smoothly, and airtight connections can be obtained. Further, even when the cross-sections of both the catheter lumens and extension tube lumens are circular, it is possible to connect extension tubes of substantially similar diameter to the catheter lumens, and increased fluid resistance of the lumens can thus be avoided. Thus, this invention provides a method for manufacturing a multi-luminal catheter comprising: providing a catheter body made of a thermoplastic material having a main part, a flared base and multiple lumens of form different from the external shape of ends of extension tubes to be connected to the catheter body; inserting into the lumens in the flared base of said catheter body, cores of substantially similar external form as the external shape of said ends of the extension tubes; heating and softening that portion of the catheter body into which cores have been inserted; introducing said heated and softened portion of the catheter into a mold so as to create connectors having openings corresponding to the external form of the cores; cooling the said portion of the catheter body into which cores have been inserted; and withdrawing said cores from said catheter body. In this method, as the multi-luminal catheter with extension tube connectors is made in such a way that the connector openings have identical shapes to the external form of the tube connecting ends, the tube connections can be made smoothly, and airtight connections can be obtained. In molding the extension tube connector of the catheter body by said heat molding process, it is preferable the parts to be molded are first pre-heated to the softening temperature, and then introduced into the mold while applying heat in stages. This invention also provides a method for manufacturing a multi-luminal catheter assembly comprising a multi-luminal catheter body wherein said extension tube connectors are first shaped to correspond to the external form of the ends of extension tubes, several extension tubes of which the ends are inserted into the connectors of said catheter body, and fixing members which entirely cover the connectors between said catheter body and said extension tubes, and part of the catheter body and the extension tubes near these connectors. In this multi-luminal catheter assembly, after the catheter body and the extension tubes are connected, the connectors are fixed en bloc by covering them with a fixing member. As a result, better airtightness and joint strength are obtained than in the case where said multi-luminal catheter is used alone. Thus, this invention also provides a method of manufacturing a multi-luminal catheter assembly which comprises: manufacturing a multi-luminal catheter as described above; inserting connecting ends of several extension tubes respectively into the openings of said connectors; then securing the extension tubes, and entirely covering the connectors between said catheter body and said extension tubes, and part of the catheter body and the extension tubes near these connectors by a fixing member. In this method, said fixing member may consist only of adhesive, or it may consist of an outer casing and a filler filling the space inside the outer casing. Further, said outer casing may consist of a casing body with the form of a tube, and a cap connected to the open end of the casing. Fig. 1(a) is a sectional view of the base of the multi-luminal catheter made according to the present invention; Fig. 1(b) is a sectional view taken along the dotted line -- in Fig. 1(a); Fig. 2(a) is a sectional view of the molding mechanism which explains the method of manufacturing the multi-luminal catheter of this invention; Fig. 2(b) is a sectional view taken along the dotted line -- in Fig. 2(a); Fig. 3(a) is a sectional view of the molding mechanism which explains the processes following Fig 2(a); Fig. 3(b) is a sectional view taken along the dotted line -- in Fig. 3(a); Fig. 4 is a partial sectional view showing the catheter body connected with the extension tubes; and Fig. 5 is a partial sectional view showing a multi-luminal catheter made according to the method of this invention. We shall now explain embodiments of this invention with reference to the drawings. First, as shown in Fig. 1(a), the catheter body 1 is formed comprising a main part 1a of specified shape, and a flared base 1b with a taper for connecting extension tubes. This catheter body may be formed by any convenient method. It should however preferably be formed continuously by extrusion molding with control of resin discharge, stretching rate and external pressure of the lumens, and then cut into desired lengths. In this way, a catheter body 1 with 4 lumens 2a - 2d of non-circular cross-section as shown in Fig. 1b is obtained. The thermoplastic material of catheter body 1 may be one of the conventional resins such as polyvinyl chloride, polyurethane, silicone resin and ethylene-vinyl acetate copolymer (EVA). Next, as shown in Figs. 2a and 2b, cores 4 of substantially similar form to the extension tube 3 that is to be connected (see Fig. 4), are pressed into lumens 2a - 2d to the necessary depth. Cores 4 should preferably consist of brass or stainless steel. Subsequently, only the part of the catheter body 1 into which cores 4 have been inserted, is introduced into mold 5 and heated by hot air. The heating temperature should preferably be sufficient to slightly soften the catheter body 1. If the catheter body 1 is of polyvinyl chloride, this temperature is approx. 40 - 90°C. The mold may be any of the molds normally used, but should preferably be of stainless steel if the cooling is done by means of water. The heating carried out to raise the catheter body 1 to the softening temperature may be carried out before introducing it into mold 5, following which the catheter body 1 may be introduced into mold 5 while continuing the heating. Further, apart from hot air, the heating may be effected by a heating wire, ultrasonic waves, high frequencies or a combination of any of these methods. The catheter body 1 is then pulled into the mold 5 while heating that part (flared base) 1b of body 1 which is to be molded. The pulling of body 1 is temporarily stopped when its end 1c is 5- 20 mm in front of the entrance 5a of mold 5, and the part 1b is then heated to a higher temperature. This temperature should be high enough to fully deform the part 1b, and if the catheter body 1 is of polyvinyl chloride, for example, it should preferably be approx. 100 - 150°C When the part 1b to be molded has reached the deformation temperature, the catheter body 1 is pulled completely into mold 5, and heating is continued for a further 1 - 2 minutes. In this way, circular openings 2e - 2h identical to the shape of cores 4 will be formed in the connecting end of catheter body 1 when the cores are removed (see Fig. 3b). Subsequently, mold 5 is cooled by means of air or water cooling, the catheter body 1 is removed from mold 5, and cores 4 are removed from openings 2e - 2h to complete the molding process. In this way, by separating the heating of the part 1b of catheter body 1 to be molded into several stages, the optimum temperatures for pulling the body 1 in and for molding can be selected, and the molding process can proceed smoothly. As the lumens 2e - 2h of catheter body 1 molded by the above process, are identical to the external form of the extension tubes, the extension tubes can be inserted in smoothly and airtight connections can be obtained. The connection of extension tubes 3 to lumens 2e - 2h of catheter body 1 can be made by pushing the tubes 3 coated with adhesive into the lumens 2e - 2h, and hardening the adhesive (see Fig. 4). Examples of adhesives that can be used are epoxy adhesives, polyurethane adhesives, acrylic adhesives, EVA adhesives, silicone adhesives and phenolic adhesives, a suitable adhesive being chosen from this list. Further, apart from said adhesive method, the connection may be made by solvent welding with solvents such as ketones, esters, chlorinated hydrocarbon or aromatic hydrocarbons, by ultrasonic fusion, or by high frequency fusion. The connection between said multi-luminal catheter and extension tubes has far superior airtightness and joint strength to conventional multi-luminal catheters, and if a fixing member is used to cover the connections between catheter body 1 and extension tubes 3, and the area near the connections, even better airtightness and joint strength can be obtained. Fig. 5 shows an embodiment of a multi-luminal catheter assembly using such a fixing member. As shown in Fig. 5, the area near the connector of the catheter body 1 with extension tubes 3 connected, is covered by a casing body 7 of which part has an inner diameter larger than the external diameter of the flared base 1b of catheter body 1, and the space between the casing body and the catheter body is filled with a resin 8 for filling. A cap 9 penetrated with extension tube 3 is then pushed into the open end of the casing body 7, and joined to the casing body 7 by means of adhesive, ultrasonic waves or high frequency waves so as to complete the assembly. In the multi-luminal catheter assembly so obtained, the connector between the catheter body 1 and extension tubes 3, and the neighboring part of the catheter and the extension tubes are entirely covered, so the joint has improved airtightness and strength than if the catheter body 1 were used alone. Any material may be used for the casing body 7 provided it has the required strength, suitable examples being polycarbonate, polypropylene, ABS resin and polyvinyl chloride. Further, the filler 8 used to fill the casing body 7 may be an epoxy resin, silicone resin, polyurethane resin, acrylic resin, EVA resin, phenolic resin or vinyl chloride resin. In the above example, both casing body 7 and cap 9 are used as fixing members. In the multi-luminal catheter assembly made according to this invention, however, instead of this arrangement, the catheter body may for example be covered and fixed by an outer casing of one piece construction not separated into a casing body and cap, or simply by a layer of adhesive without using an outer casing.

Claims: A method for manufacturing a multi-luminal catheter comprising: providing a catheter body (1) made of a thermoplastic material having a main part (1a), a flared base (1b) and multiple lumens (2a-2d) of form different from the external shape of ends of extension tubes to be connected to the catheter body; inserting into the lumens in the flared base (1b) of said catheter body, cores (4) of substantially similar external form as the external shape of said ends of the extension tubes; heating and softening that portion of the catheter body into which cores (4) have been inserted; introducing said heated and softened portion of the catheter into a mold (5) so as to create connectors having openings (2e-2h) corresponding to the external form of the cores; cooling the said portion of the catheter body into which cores have been inserted; and withdrawing said cores from said catheter body. The method as in claim 1, characterized in that said portion of the catheter body (1) into which cores (4) have been inserted is first heated to the softening temperature of the catheter body before introducing said portion into the mold (5), and said portion is then introduced into the mold while applying heat in stages. The method as in claim 2, characterized in that said portion of the catheter body is first heated to the softening temperature of the material of said catheter body before introducing said portion in the mold or after it has been partially introduced, said portion to be molded is then partially introduced into said mold and heated to a temperature sufficient to deform the catheter body, and substantially the whole portion into which cores have been inserted is then introduced into said mold, molded and cooled so as to form said openings of said connectors. A manufacturing method as in anyone of claims 1 to 3, wherein the heating of the catheter body (1) is effected by means of hot air, heating wire, ultrasonic waves or high frequency, or by a combination of these techniques. A method of manufacturing a multi-luminal catheter assembly characterized by: manufacturing a multi-luminal catheter according to anyone of claims 1 to 4; inserting connecting ends of several extension tubes (3) respectively into the openings (2e-2h) of said connectors. then securing the extension tubes (3), and entirely covering the connectors between said catheter body and said extension tubes, and part of the catheter body and the extension tubes near these connectors by a fixing member. A method of manufacturing a multi-luminal catheter assembly as in claim 5, wherein said fixing member is comprised only of an adhesive. A method of manufacturing a multi-luminal catheter assembly as in claim 5, wherein said fixing member comprises an outer casing (7, 9) and a filler (8) filled inside the casing, and the space between the casing, outer surface of the catheter body and outer surface of the extension tubes (3) being filled with the filler after inserting the catheter body into said casing. A method of manufacturing a multi-luminal catheter assembly as in claim 7, wherein said outer casing comprises a casing body (7) and a cap (9) connected to its open end, and the cap being connected to the casing body after filling the space between the casing body, outer surface of the catheter body (1) and outer surface of the extension tubes (3) with adhesive.

Inventors: ISHITSU YOSHIO, SEKII SHIGEKAZU, TSUCHIDA KOUJI, ISHITSU, YOSHIO, SEKII, SHIGEKAZU, TSUCHIDA, KOUJI
Applicants: TERUMO CORP, TERUMO KABUSHIKI KAISHA
Application year: 1988
Main classification: A61M25
IPC codes: A61M25