Catheter-to-extension tube assembly and method of making same

A catheter assembly (10) having a catheter (12) with lumens (20a,20b), extension tubes (14a,14b) and a hub (16). Distal ends (36) of the extension tubes and the proximal end (24) of the catheter are secured in and to the hub. Fittings (50) are first affixed in the distal ends of the extension tubes and have annular collars (56) that are embedded in the hub when the hub is molded over the distal ends of the extension tubes during manufacturing. An array of annular barbs (60) secure the cylindrical portion (52) of each fitting in the respective extension tube distal end (36).

FIELD OF THE INVENTION

This relates to the field of medical devices, and more particularly to catheter assemblies.

BACKGROUND OF THE INVENTION

Vascular catheters having extension tubes joined to their proximal ends are known, with catheters conventionally being made of either silicone or polyurethane while the extension tubes are polyurethane or polymers other than silicone. One manner of connecting an extension tube to a catheter lumen is to provide complementary luer fittings on both the proximal catheter end and the distal tube end, for removable connections. Another manner of connection, especially for use on multi-lumen catheters, is to provide a hub component that is affixed to the proximal end of the catheter and to the distal ends of one or more extension tubes associated with respective lumens of the catheter; the hub provides a channel or passageway establishing fluid communication between each extension tube and a respective lumen of the catheter, defining a catheter assembly. Commonly, the hub is insert molded of polyurethane onto the respective catheter and extension tube ends with the use of mandrels that define the channels of the hub during molding. Use of such assemblies is well known for hemodialysis and for infusion of medication into or drawing of blood from a patient, or both.

Molding of a hub onto a proximal end of a multi-lumen catheter simultaneously with molding it onto the distal ends of a plurality of extension tubes associated with the catheter lumens, is known. One such molding process is disclosed in U.S. Patent Publication No. 2005/0080398, which disclosure is incorporated hereinto by reference, including the use of mandrels extending from within the extension tube passageways and into the associated lumens of the catheter at the proximal ends thereof. The mandrel portions extending between the extension tube distal ends and the catheter proximal end define passageways through the hub body formed within a hub mold to surround end portions of the extension tubes and the catheter and seal with outer surfaces thereof, which hub passageways define fluid communication between the extension tube passageways and the respective lumens.

It is desired to provide a manner of connecting a catheter lumen to a respective extension tube where the extension tube may be made at least partly of silicone.

BRIEF SUMMARY OF THE INVENTION

Briefly, the present invention provides a method of manufacturing a catheter assembly that includes a hub and at least one extension tube that is at least partly of silicone. A generally cylindrical fitting has a passageway therethrough, an annular collar at one end, and an at least one annular barb therearound having its angled surface facing away from the collar and a substantially perpendicular surface facing the collar. The diameter of each at least one barb is larger than the inner diameter of the passageway of the extension tube. The fitting is first inserted into a distal end of the extension tube. Preferably, an array of at least two or three annular barbs are provided on the fitting, and the angles thereof are preferably small for ease of insertion into the extension tube distal end and for minimizing the damage to the extension tube, since the fitting expands the extension tube inner diameter during insertion. The barbs will act to prevent movement of the extension tube relatively away from the fitting.

The distal end of the extension tube, including the fitting affixed thereinto, is placed into a mold cavity in which the hub will be molded, and the catheter proximal end is also placed into the mold cavity, with mandrels extending through the extension tube (and fitting) and the catheter such that portions of the mandrels also extend through the mold cavity. The hub is then molded therearound, after which the mandrels are removed from the molded assembly. In the completed assembly, the fitting will secure the extension tube to the proximal end of the hub by reason of the annular collar surrounded by molded material of the hub, especially proximally of the collar. A plurality of such extension tubes with fittings would be simultaneously molded and embedded within a hub in the same fashion, for a multi-lumen catheter.

The extension tube comprises silicone and preferably a thin outer layer is provided thereover of polyurethane. The silicone has better shape memory to resist deformation by Roberts clamps and the like, and also has greater lubricity facilitating the passing therethrough of a guide wire, during insertion of the catheter into a patient, but has a disadvantage of less-than-optimum adhesion to and sealing with the polyurethane material of the hub during insert molding thereof. The thin outer layer of polyurethane provides for sealing with the molded hub, while the fitting of the present invention assures that the extension tube is firmly secured to the hub.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The terms “distal” and “proximal” refer, respectively, to directions closer to and away from the insertion tip of a catheter in an implantable catheter assembly. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiments illustrated below are not intended to be exhaustive or to limit the invention to the precise form disclosed. These embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention.

Catheter assembly10inFIGS. 1 and 2includes a dual lumen catheter12, a pair of extension tubes14a,14band a hub16, with luer fittings18affixed to proximal ends of the extension tubes. Each extension tube is in fluid communication with a respective lumen of catheter12, which lumens20a,20bare of a conventional D-shaped cross-section where the lumens are separated by an internal wall or septum22, seen inFIG. 3. Lumen20ais aligned with a corresponding passageway28aof hub16along a coincident axis that is also the axis of the respective extension tube14a, while lumen20bis foreshortened at26to enable an angled passageway28bof the hub to have a short portion that is coincident with the longitudinal axis of the lumen20bwhile the angled passageway portion is coincident with the axis of extension tube14b.

FIG. 3also shows fittings50secured to the distal ends of each extension tube14a,14b, each of the fittings including an enlargement such as an annular collar56at the end face of the respective extension tube that protrudes radially beyond the outer diameter of the extension tube to establish a stop section securing the fitting and therefore the extension tube to the hub16upon insert molding of the hub to the distal ends of the extension tubes and the proximal end24of the catheter.FIG. 3also depicts that the fitting having a distal enlargement embedded within the hub proximal end portion distally of a portion of the hub is smaller in dimension than the distal enlargement of the fitting.

FIGS. 4 and 5illustrate an extension tube14a,14bhaving a fitting50secured thereto, the fitting having a tubular proximal section52disposed within the passageway34of the extension tube and having a passageway54in fluid communication with passageway34. The fitting further includes a distal enlargement such as annular collar56, with annular collar56positioned adjacent to the end face of the extension tube and protruding radially outwardly to a diameter greater than the outer diameter of the extension tube even after the tube's distal end portion36has been expanded to fit over the fitting. The annular collar assures that the extension tube with its fitting remains mechanically anchored within and assuredly secured to the hub. Best seen inFIG. 7, fitting50extends to a proximal end58and is provided with at least one, preferably two or three barbs60therealong protruding radially outwardly. Fitting passageway54extending therethrough having an inner diameter matching that of passageway34of the extension tube. Barbs60secure the fitting in the distal end of extension tube14a,14bwhen fitting50is pressed into the distal end of the tube, with sharply angled barb faces62that are directed distally to prevent the extension tube from moving proximally from the fitting thereafter while gently sloping proximal faces64facilitate insertion of the fitting into the extension tube. The extension tube is expanded slightly at distal end36by the fitting50, and grips the fitting tightly, after the fitting is pressed thereinto.

As shown inFIG. 6, preferably the extension tube comprises an inner layer30of substantial thickness of silicone, and a thin, outer layer32of polyurethane. The inner layer of silicone provides the advantages of better shape memory for the extension tube to consistently retain its intended undeformed cylindrical inner diameter even after repeatedly being clamped and unclamped by a Roberts clamp (not shown). The outer layer of polyurethane assures sealing with the polyurethane hub material therearound by fusing therewith.