WO2001056630A1

WO2001056630A1 - Apparatus for the dialysis of blood, method for fabricating the same, and method for the dialysis of blood

Info

Publication number: WO2001056630A1
Application number: PCT/US2001/003330
Authority: WO
Inventors: Frank R. Prosl; Harold M. Martins; Brian K. Estabrook; Paul J. Smith
Original assignee: Biolink Corporation
Priority date: 2000-02-02
Filing date: 2001-02-01
Publication date: 2001-08-09
Also published as: AU2001231278A1

Abstract

Improved apparatus for the dialysis of blood, a method for fabricating the same, and an improved method for the dialysis of blood.

Description

APPARATUS FOR THE DIALYSIS OF BLOOD,

METHOD FOR FABRICATING THE SAME, AND

METHOD FOR THE DIALYSIS OF BLOOD

Cross-Reference To Related Application

This is a continuation-in-part of pending prior U.S. Patent Application Serial No. 09/251,572, filed February 17, 1999 by Harold M. Martins et al. for APPARATUS FOR THE DIALYSIS OF BLOOD, METHOD FOR FABRICATING THE SAME, AND METHOD FOR THE DIALYSIS OF BLOOD.

Field Of The Invention

This invention relates to the dialysis of blood in general, and more particularly to apparatus and methods for use in the same.

Background Of The Invention

A healthy kidney removes toxic wastes and excess water from the blood. In End Stage Renal Disease ("ESRD") , or chronic kidney failure, the kidneys progressively stop performing these essential functions over a long period of time. When the kidneys fail, a patient dies within a short period of time unless that patient receives dialysis treatment for the rest of that patient's life or undergoes transplantation of a healthy, normal kidney. Since relatively few kidneys are currently available for transplantation, the overwhelming majority of patients with ESRD receive dialysis treatment.

Hemodialysis therapy is an extracorporeal (i.e., outside the body) process which removes toxins and water from a patient's blood. A hemodialysis machine pumps blood from the patient, through a dialyzer, and then back to the patient. The dialyzer removes the toxins and water from the blood by a membrane diffusion process. Typically, a patient with chronic kidney disease requires hemodialysis three times per week, for 3-6 hours per session. Removing blood from the body requires a vascular access to the patient's blood system.

One common method for accessing a patient's blood system for hemodialysis involves the use of a percutaneous catheter assembly. The percutaneous catheter assembly is inserted into a major vein, such as the femoral, subclavian or jugular vein. For long term maintenance dialysis, the jugular vein is generally the preferred insertion site. The catheter assembly is percutaneous, with one end external to the body and the other end dwelling in either the superior vena cava or the right atrium of the heart. The external portion of the catheter assembly has connectors permitting attachment of blood lines leading to and from the hemodialysis machine.

Figs. 1 and 2 show the traditional manner of positioning a percutaneous catheter assembly 5 relative to the body. More particularly, percutaneous catheter assembly 5 generally comprises a catheter portion 10 comprising a dual-lumen catheter element 15, and a connector portion 20 comprising an extracorporeal connector element 25. The catheter assembly's extracorporeal connector element 25 is disposed against the chest 30 of the patient, and the distal end 35 of catheter element 15 is passed into the patient's internal jugular vein 40 (Fig. 2) and then down into the patient's superior vena cava 45 (as used herein, the terms "distal" and "proximal" are intended to be relative to the position of connector portion 20) . More particularly, the distal end 35 of catheter element 15 is positioned within the patient's superior vena cava 45 such that the mouth 50 of suction line 55, and the mouth 60 of return line 65, are both located between the patent's right atrium 70 and the patient's left subclavian vein 75 and right subclavian vein 80. Alternatively, the distal end 35 of catheter element 15 may be positioned so that mouth 50 of suction line 55, and mouth 60 of return line 65, are located within the patient's right atrium 70. The percutaneous catheter assembly 5 is then left in this position relative to the body, waiting to be used during an active dialysis session.

When hemodialysis is to be performed on the patient, the catheter assembly's extracorporeal connector element 25 is appropriately connected to a dialysis machine (not shown), i.e., suction line 55 is connected to the input port (i.e., the suction port) of the dialysis machine, and return line 65 is connected to the output port (i.e., the return port) of the dialysis machine. The dialysis machine is then activated (i.e., the dialysis machine's blood pump is turned on and the flow rate set) , whereupon the dialysis machine will withdraw relatively "dirty" blood from the patient through suction line 55 and return relatively "clean" blood to the patient through return line 65.

It has also been proposed to use a subcutaneous port and catheter assembly to provide vascular access for hemodialysis.

More particularly, a subcutaneous port and catheter assembly 82 is shown in Figs. 3-5. Looking first at Fig. 3, subcutaneous port and catheter assembly 82 generally comprises a connector portion 84 comprising a subcutaneous port element 86, and the aforementioned catheter portion 10 comprising the dual-lumen catheter element 15. As noted above, the catheter element 15 in turn comprises the suction line 55 and the return line 65. Subcutaneous port element 86 includes a needle port 88 which is connected to suction line 55, and a needle port 90 which is connected to return line 65. The distal end of suction line 55 terminates in the aforementioned mouth 50, and the distal end of return line 65 terminates in the aforementioned mouth 60.

Figs. 4 and 5 show subcutaneous port and catheter assembly 82 positioned within the body. More particularly, the assembly's port element 86 is disposed under the skin of the patient (e.g., in the chest area of the patient), and the assembly's catheter element 15 is passed into the patient's internal jugular vein 40 and then down into the patient's superior vena cava 45. The distal end of the assembly's catheter element 15 may be positioned within the patient's superior vena cava 45 such that mouth 50 of suction line 55, and mouth 60 of return line 65, are both located approximately between the patient's right atrium 70 and the patient's left subclavian vein 75 and right subclavian vein 80. Alternatively, the distal end of catheter element 15 may be positioned so that mouth 50 of suction line 55, and mouth 60 of return line 65, are located within the patient's right atrium 70. The subcutaneous port and catheter assembly 82 is then left in this position within the body, waiting to be used during an active dialysis session.

When hemodialysis is to be performed on the patient, the assembly's subcutaneous port element 86 is appropriately connected to a dialysis machine, i.e., needle port 88 is connected to the input port (i.e., the suction port) of the dialysis machine with an appropriate percutaneous needle (not shown) , and the assembly' s needle port 90 is connected to the output port (i.e., the return port) of the dialysis machine with an appropriate percutaneous needle (not shown) . The dialysis machine is then activated, whereupon it will withdraw relatively "dirty" blood from the patient through suction line 55 and return relatively "clean" blood to the patient through return line 65.

It will be appreciated that both percutaneous catheter assembly 5 (Figs. 1 and 2) and subcutaneous port and catheter assembly 82 (Figs. 3-5) comprise the catheter portion 10, which in turn comprises the dual-lumen catheter element 15, with the distal end of the catheter element normally dwelling in the patient's vascular system.

Inasmuch as a substantial portion of catheter element 15 dwells in the patient's vascular system (e.g., within internal jugular vein 40 and superior vena cava 45) , it is desirable for the catheter element to have the smallest possible outside diameter so as to minimize interference with normal blood flow. At the same time, however, it is also desirable for the catheter element to have the largest possible inside diameter so that maximum dialysis blood flow can be achieved. Thus, from the standpoint of blood flow alone, it is desirable for the catheter element to have the thinnest possible wall thickness.

Unfortunately, however, other considerations also come into effect. For one thing, it is also important that the catheter element have the highest possible burst strength so that it will not fail when passing blood under pressure. In addition, it is also important that the catheter element be able to withstand high negative pressures without collapsing, so that blood can be withdrawn from the body at a rapid rate. Furthermore, it is important that the catheter element be capable of being bent at a substantial angle without kinking, such as, for example, at the point where the catheter element undergoes a large deflection in order to enter internal jugular vein 40 (see Figs. 1 and 4) . These and other considerations tend to significantly limit the degree to which the catheter element's wall thickness can be reduced.

Furthermore, the choice of materials for forming the catheter element is also limited, since the element is typically deployed in the patient's body for substantial periods of time. Currently, silicone rubber is the accepted material for forming catheter elements for use in percutaneous catheter assemblies and subcutaneous port and catheter assemblies.

The foregoing factors have, collectively, tended to limit either (1) the degree to which the outside diameter of the catheter element can be reduced, and/or (2) the degree to which the inside diameter of the catheter element can be enlarged, and/or (3) the rate at which blood can be introduced into the patient's body through the catheter element, and/or (4) the rate at which blood can be withdrawn from the patient's body through the catheter element, and/or (5) the degree to which the catheter element can be bent without kinking.

In U.S. Patent No. 5,041,098, issued August 20, 1991 to Loiterman et al., it was suggested that a helically wound reinforcement wire could be incorporated into the side wall of the catheter element. Such a suggestion could appear to be advantageous, since it could enable the walls of the catheter element to be made thinner yet stronger.

Unfortunately, in practice, Applicants have found that commercially-available coil-reinforced silicone rubber tubes lack the smooth interior lumen desirable for hemodialysis applications.

More particularly, Applicants have discovered that in hemodialysis applications, smooth lumen walls are important for (1) providing the laminar blood flows required for high volume blood transfer, (2) avoiding the creation of irregular blood currents and the creation of blood stagnation areas, (3) avoiding the formation of blood clots, (4) eliminating breeding areas for bacteria, and (5) facilitating flush-cleaning of the apparatus after dialysis has taken place.

Unfortunately, Applicants have also found that commercially-available coil-reinforced silicone rubber tubes lack the smooth interior lumen desirable for hemodialysis applications.

It is believed that this may be due to the facts that (1) commercially-available coil-reinforced silicone rubber tubes are generally used for purposes other than dialysis applications, and (2) the importance of smooth interior lumens has not yet been discovered by the dialysis industry.

It is also believed that commercially-available coil-reinforced silicone rubber tubes may lack the smooth interior lumen desirable for hemodialysis applications due to the manner in which such tubes are typically formed.

More particularly, it is believed that commercially-available coil-reinforced silicone rubber tubes are generally formed by (1) creating an outer tube out of silicone rubber, (2) forcing that tube open, (3) inserting the coil spring inside the forced-open silicone rubber tube, (4) releasing the outer tube so that it contracts back on the coil spring, and (5) dip molding an interior layer of silicone rubber onto the spring and the interior lumen of the outer tube. While such a process is generally adequate for capturing the coil spring within a body of silicone rubber material, it also results in an undulating interior lumen, since the process essentially covers the coil spring and the interior lumen of the outer tube with a substantially constant- thickness dip layer. Coil-reinforced silicone rubber tubes formed with the aforementioned process are not smooth enough for good hemodialysis applications.

In addition to the foregoing, inquiries of persons knowledgeable in the field of coil-reinforced silicone rubber tubes failed to locate anyone with experience in forming interior lumens smooth enough for use in hemodialysis applications.

As noted above, the use of two tubes in blood dialysis has entailed the positioning of two tubes in the blood system of a patient, one tube for suction of blood, and the other for return of blood to the patient, as described above. Maintaining two tubes in an artery or vein occupies a substantial portion of the cross-section of the artery or vein, causing a reduction in blood flow therethrough.

Efforts have been made to reduce the cross-sectional area of the suction and return tubes by combining two lumens in a single tubular member and, in addition, having the return lumen portion of the tubular member collapsible. Accordingly, when there is no dialysis operation underway, and therefore no internal pressure exerted on the interior of the return lumen, the return lumen is in a collapsed state and occupying relatively little cross-sectional area, thus permitting improved blood flow. This can be extremely helpful, particularly when one considers that a typical hemodialysis patient undergoes active hemodialysis only three times per week, for 3-6 hours per session.

In U.S. Patent No. 5,868,717, issued February 9, 1999 to Frank R. Prosl, there is shown and described a dual-lumen catheter in which the return lumen is collapsible when not internally pressurized, thereby providing for reduced cross-sectional presence in the artery, and hence improved blood flow, between active dialysis sessions.

With the dual-lumen catheter of U.S. Patent No. 5,868,717, the suction lumen is fully open at all times. To maintain the suction lumen in an open condition, the tubular member, in the area of the suction lumen, is provided with a side wall of sufficient thickness to continuously support the open condition.

While the catheter of U.S. Patent No. 5,868,717 has facilitated a substantial reduction the in cross-sectional presence of the two lumens between active dialysis sessions, there remains a need to reduce the cross-sectional area of the catheter distal end portion still further, to permit blood flow through the artery in which the catheter is maintained, as close to normal as possible.

Objects Of The Invention

Accordingly, one object of the present invention is to provide improved apparatus for use in the dialysis of blood.

Another object of the present invention is to provide an improved catheter element for use in the dialysis of blood, wherein the catheter element may be used in either a percutaneous catheter assembly or a subcutaneous port and catheter assembly.

And another object of the present invention is to provide an improved catheter element which has the largest possible interior diameter and the smallest possible exterior diameter, yet is resistant to bursting, collapse and kinking.

Still another object of the present invention is to provide an improved catheter element which incorporates reinforcing means within the side wall of the catheter, yet has an interior lumen which is sufficiently smooth that the catheter element may be used in hemodialysis applications with good results. And another object of the present invention is to provide a support structure at the distal end of the catheter element to help maintain openness of the flow path through the catheter element.

Still another object of the present invention is to provide an improved catheter element having an improved tip geometry so as to help maintain openness of the flow path through the catheter element.

Yet another object of the present invention is to provide an improved method for fabricating apparatus for use in the dialysis of blood.

And another object of the present invention is to provide an improved method for the dialysis of blood.

Still another object of the present invention is to provide a catheter in which two lumens are defined by a single flexible tubular member, and in which one of the two lumens is provided with a thin wall reinforced by structure therearound, and the other of the two lumens is provided with a collapsible wall, such that the catheter provides two lumens in use in a blood dialysis operation, each of a large internal diameter, and two lumens, one of which is collapsed, when the catheter is not active but maintained in place. In the latter condition, the diameter, or width-wise dimension of the catheter tubular member, is preferably only slightly in excess of the outside dimension of one lumen.

Still further objects of the invention are to provide an apparatus for use in the dialysis of blood, and a method for the dialysis of blood, utilizing the catheter described immediately above, and a still further object of the invention is to provide a method for making the catheter described immediately above.

Summary Of The Invention

These and other objects are addressed by the present invention, which comprises improved apparatus for the dialysis of blood, a method for making the same, and an improved method for the dialysis of blood.

In one preferred embodiment, the present invention comprises a catheter comprising an elongated flexible tubular member formed of a biocompatible material and defining first and second lumens extending therethrough end to end. A reinforcing structure is encased by the material and reinforces side walls of only the first lumen, the second lumen being defined by side walls collapsible when the second lumen is devoid of internal pressurization.

In another preferred embodiment, the present invention comprises apparatus for use in the dialysis of the blood of a patient, the apparatus comprising a connector portion and a catheter portion, the connector portion comprising an outlet adapted for communication with a line connected to an input port of a dialysis machine, and an inlet adapted for communication with a line connected to an output port of a dialysis machine, and the catheter portion comprising a catheter member comprising an elongated flexible tubular member defining first and second lumens extending therethrough end to end, the member being formed of a biocompatible material, a reinforcing structure encased by the material and reinforcing side walls of only the first lumen, the second lumen being defined by side walls collapsible when the second lumen is devoid of internal pressurization, the first and second lumens each having an interior surface sufficiently smooth for use in hemodialysis applications. A proximal end of a first lumen portion of the tubular member is connected to the connector portion and in communication with the outlet, and a distal end of the first lumen portion of the tubular member terminates in a suction line mouth. A proximal end of a second lumen portion of the tubular member is connected to the connector portion and in communication with the inlet, and a distal end of the second lumen portion of the tubular member terminates in a return mouth. The tubular member is adapted for disposition within the body of the patient so that the suction line mouth and the return line mouth are both disposed in the vascular system of the patient.

In accordance with a further feature of the present invention, there is provided a method for making a catheter, the method comprising the steps of:

(a) providing an elongated molding core;

(b) forming a sleeve of biocompatible material on the molding core;

(c) positioning reinforcing structure on an outer surface of the sleeve;

(d) positioning a lumen mandrel adjacent to the reinforcing structure and extending alongside the molding core; (e) forming an overlayer of biocompatible material over the sleeve, the reinforcing structure, and the lumen mandrel; and

(f) removing the lumen mandrel to provide a lumen, and removing the molding core to provide a further lumen.

In yet another preferred embodiment, the present invention comprises a method for making a catheter, the method comprising the steps of:

(a) providing an elongated molding core;

(b) forming a sleeve of biocompatible material on the molding core, the sleeve defining a first lumen therethrough;

(c) positioning reinforcing structure on an outer surface of the sleeve;

(d) positioning a lumen mandrel adjacent the reinforcing structure and extending alongside the molding core;

(e) forming an overlayer of biocompatible material over the sleeve, the reinforcing structure, and the lumen mandrel;

(f) removing the lumen mandrel from the overlayer; (g) inserting a forming core in the opening in the overlayer formed by the lumen mandrel;

(h) engaging the overlayer, adjacent to the forming core, with a forming mandrel so as to form, between the forming core and the forming mandrel, a second lumen in a collapsed and expandable state;

(i) removing the forming core so as to provide the second lumen in the catheter; and

(j) removing the molding core from the sleeve so as to provide the first lumen in the catheter. In accordance with a further feature of the present invention, there is provided a method for making a catheter, the method comprising the steps of:

(a) providing an elongated molding core;

(b) forming a sleeve of biocompatible material on the molding core;

(c) positioning reinforcing structure on an outer surface of the sleeve;

(d) positioning a lumen mandrel adjacent to the reinforcing structure and extending alongside the molding core; (e) forming an overlayer of biocompatible material over the sleeve, the reinforcing structure, and the lumen mandrel;

(f) removing the lumen mandrel so as to provide an opening through the catheter;

(g) applying a form tool to the overlayer, adjacent to the tunnel, so as to provide a lumen in a collapsed and expandable state; and

(h) removing the molding core so as to provide a further lumen.

In another preferred embodiment, the present invention comprises a method for the dialysis of the blood of a patient, the method comprising the steps of:

(a) providing a dialysis machine, and providing apparatus comprising a connector portion and a catheter portion; the connector portion comprising an outlet adapted for communication with a line connected to an input port of the dialysis machine, and an inlet adapted for communication with a line connected to an output port of the dialysis machine; and the catheter portion comprising a catheter element comprising; a suction lumen and a return lumen, each of the lumens being disposed in a single flexible tubular member, the tubular member having side walls defining the suction and return lumens, the side walls (1) being formed of a biocompatible material, (2) encasing a reinforcing structure therein for reinforcing portions of the side walls surrounding only the suction lumen, and (3) having smooth interior surfaces for defining the lumens, the interior surfaces being sufficiently smooth for hemodialysis applications; a proximal end of the suction lumen being connected to the connector portion and in communication with the outlet, and a distal end of the suction lumen terminating in a suction lumen mouth; a proximal end of the return lumen being connected to the connector portion and in communication with the inlet, and a distal end of the return lumen terminating in a return lumen mouth; the suction lumen and the return lumen being adapted for disposition within the body of the patient so that the suction lumen mouth and the return lumen mouth are both disposed in the vascular system of the patient;

(b) placing the lumen mouths in the vascular system of the patient;

(c) connecting the connector outlet to the input port of the dialysis machine, and connecting the connector inlet to the output port of the dialysis machine; and

(d) operating the dialysis machine.

In another preferred embodiment, the present invention comprises a catheter comprising an elongated flexible tubular element defining a lumen extending therethrough end to end, the member being formed of a biocompatible material, and a reinforcing structure encased by the material and reinforcing side walls of the lumen, the reinforcing structure having a variable density along its length.

And in another preferred embodiment, the present invention comprises a catheter comprising an elongated flexible tubular element defining first and second lumens extending therethrough end to end, the member being formed of a biocompatible material, wherein the first lumen comprises a suction lumen for removing blood from a patient's vascular system, and the second lumen comprises a return lumen for returning blood to the patient's vascular system, a distal end of the first lumen being distal to a distal end of the second lumen, and further wherein a flow diverter is disposed between the distal end of the first lumen and the distal end of the second lumen so as to reduce the possibility that blood exiting the second lumen will be drawn into the first lumen.

Brief Description Of The Drawings

These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which are to be considered together with the accompanying drawings wherein:

Fig. 1 is a schematic view of a percutaneous catheter assembly installed in a patient;

Fig. 2 is a schematic view showing the distal end of the catheter element of the percutaneous catheter assembly of Fig. 1 installed in a patient, with the direction of blood flow being indicated by appropriate arrows;

Fig. 3 is a schematic view of a subcutaneous port and catheter assembly;

Fig. 4 is a schematic view showing the subcutaneous port and catheter assembly of Fig. 3 installed in a patient;

Fig. 5 is an enlarged schematic view showing the subcutaneous port and catheter assembly of Fig. 3 installed in a patient;

Fig. 6 is a schematic view, partially in section, of novel catheter apparatus;

Fig. 6A shows an alternative form of novel catheter apparatus;

Fig. 7 is a perspective view of a support structure incorporated into the novel catheter apparatus shown in Fig. 6:

Figs. 8-10 are schematic views illustrating how the local surface profile of the central lumen of the catheter apparatus may vary along the length of the lumen; Figs. 11-17 illustrate process steps for fabricating the novel catheter apparatus shown in Fig. 6;

Fig. 18 illustrates the distal end of an alternative form of catheter apparatus formed in accordance with the present invention;

Fig. 19 is a perspective view of the support structure incorporated into the catheter apparatus shown in Fig. 18;

Figs. 20 and 21 illustrate still other forms of support structures which may be incorporated into catheter apparatus formed in accordance with the present invention;

Fig. 22 illustrates an alternative manner for incorporating the support structure of Fig. 21 into catheter apparatus formed in accordance with the present invention;

Fig 22A illustrates an alternative manner for forming side openings near the distal end of the catheter apparatus, wherein the side openings are in the form of relatively narrow, longitudinally-extending slits; Fig. 23 illustrates catheter apparatus utilizing an alternative form of reinforcing means;

Fig. 23A schematically illustrates an alternative form of reinforcing means, wherein the reinforcing means comprise a tubular, braided mesh reinforcer;

Fig. 24 schematically illustrates the distal end of a catheter apparatus attaching itself to adjacent tissue through suction;

Fig. 25 schematically illustrates an alternative form of catheter apparatus provided with an improved tip geometry to prevent the distal end of the catheter apparatus from binding itself to adjacent tissue due to a vacuum effect;

Fig. 26 schematically illustrates another alternative form of catheter apparatus, with the apparatus having a so-called "triangle" notch;

Figs. 27A and 27B schematically illustrate still another alternative form of catheter apparatus, with the apparatus having a so-called "fork tip" configuration, and with Fig. 27B showing the catheter apparatus rotated 90 degrees about its longitudinal axis from the view of Fig. 27A; Fig. 28 schematically illustrates another alternative form of catheter apparatus, with the apparatus having an "angle cut" front tip;

Fig. 29 schematically illustrates another alternative form of catheter apparatus, with the apparatus having an "angle cut" front tip and an associated side opening;

Figs. 30-36 illustrate process steps for fabricating a novel catheter apparatus, and show one form of process and apparatus illustrative of an embodiment of the invention;

Figs. 37-43 are in part sectional, and in part end elevational views, of the steps and apparatus of Figs. 30-36, respectively;

Figs. 44 and 45 are perspective and sectional views, respectively, of the step and apparatus of Figs. 33 and 40;

Figs. 46-55 illustrate alternative process steps for fabricating a catheter apparatus;

Figs. 56-65 are in part sectional, and in part end elevational views, of the steps and apparatus of Figs. 46-55, respectively; Figs. 66-74 illustrate alternative process steps for fabricating a catheter apparatus;

Figs. 75-83 are in part sectional, and in part end elevational views, of the steps and apparatus of Figs. 66-74, respectively;

Fig. 84 is an enlarged view similar to Fig. 63;

Fig. 85 is an enlarged view similar to Fig. 65;

Figs. 86-89 are end elevational views showing alternative embodiments of catheters;

Fig. 90 is a perspective view of a catheter of the type shown in Fig. 88;

Fig. 91 is a perspective view of an alternative embodiment of catheter;

Fig. 92 is a perspective view of yet another form of catheter formed in accordance with the present invention;

Figs. 93 and 94 are end elevational views of the catheters of Figs. 91 and 92, respectively;

Figs. 95-97 show yet another form of catheter formed in accordance with the present invention; and

Fig. 98 shows yet another form of catheter formed in accordance with the present invention. Detailed Description Of The Preferred Embodiments

Looking now at Fig. 6, novel catheter apparatus 100 is shown. Catheter apparatus 100 comprises a silicone rubber tube 105 having a side wall 110, a distal end wall 115 and a proximal end wall 120. If desired, silicone rubber tube 105 may include an additive so as to render some or all of the silicone rubber tube radio-opaque. The outer surface 125 of side wall 110 has a smooth configuration so as to minimize interference with blood flow when catheter apparatus 100 is disposed in the vascular system of a patient.

A central lumen 130 extends between distal end wall 115 and proximal end wall 120. Central lumen 130 has a smooth interior surface so that blood can be passed through that lumen during a hemodialysis session with good results.

Catheter apparatus 100 also comprises reinforcing means 135 encapsulated within side wall 110 for reinforcing the side wall. In one preferred form of the invention, reinforcing means 135 comprise a coil spring 140. Reinforcing means 135 may extend along the entire length of tube 105, or reinforcing means 135 may extend along only one or more selected portions of tube 105, as preferred. For example, reinforcing means 135 might extend along only an intermediate portion of tube 105. In one form of the invention, reinforcing means 135 are formed out of a radio-opaque material or the like, whereby catheter apparatus 100 may be visualized while within the body of the patient through the use of appropriate imaging equipment, whereby to aid in the proper deployment of the apparatus within the body. If desired, the pitch of coil spring 140 may be decreased at one or more selected locations so as to render a radio-opaque coil spring more visible. In addition, multiple layers of coils may be created so as to enhance coil visibility. See, for example, Fig. 6A which shows such a construction.

Preferably, but not necessarily, at least one side opening 145 is formed in side wall 110 adjacent to, but spaced from, distal end wall 115. The at least one side opening 145 communicates with central lumen 130, whereby blood may enter and/or exit the distal end of catheter apparatus 100 via either the distal end of central lumen 130 and/or the at least one side opening 145. Preferably, the at least one side opening 145 is in the form of a substantially circular hole.

And preferably, but not necessarily, a support structure 150 (Figs. 6 and 7) is disposed at the intersection of central lumen 130 and distal end wall 115 so as to provide a stiffening element at the distal end of catheter apparatus 100. This member can help maintain openness of the flow path through catheter apparatus 100. In one form of the invention, shown in Figs. 6 and 7, support structure 150 is formed with a cylindrical configuration, with a bore 155 opening on the support structure's distal end surface 160, a counterbore 165 opening on the support structure's proximal end surface 170, and with an annular shoulder 175 formed at the intersection of bore 155 and counterbore 165. In one preferred form of the invention, support structure 150 is mounted to the distal end of tube 105 so that the support structure's distal end surface 160 lies flush with the tube's distal end surface 115, and so that the support structure's bore 155 is aligned with the tube's central lumen 130 (Fig. 6) . By way of example but not limitation, in one preferred form of the invention, tube 105 is formed out of 80 durometer silicone rubber, and has an outside diameter of approximately 0.135 inch, an inside diameter of approximately 0.105 inch, and a wall thickness of approximately 0.015 inch; and coil spring 140 is formed out of titanium, with the wire forming the coil spring being approximately 0.006 inch thick and having a coil rate of approximately 0.031-0.038 pitch. Support structure 150 is preferably formed out of a radio-opaque material, whereby the distal end of catheter apparatus 100 may be visualized while within the body of the patient through the use of appropriate imaging equipment, whereby to aid in the proper deployment of the apparatus within the body.

It is an important feature of the present invention that central lumen 130 be formed smooth enough that catheter apparatus 100 may be used for hemodialysis applications with good results. However, the presence of reinforcing means 135 in the side wall 110 of catheter apparatus 100, and/or the manner of encapsulating reinforcing means 135 within side wall 110, and/or a variety of other factors, may cause variations in the diameter of central lumen 130.

More particularly, as seen in Fig. 8, the presence of reinforcing means 135 may cause central lumen 130 to vary outwardly (as shown at 130A) in the region between adjacent occurrences of reinforcing means 135; or, as seen in Figs. 9 and 10, the presence of reinforcing means 135 may cause central lumen 130 to vary inwardly (as shown at 130B) in the region between adjacent occurrences of reinforcing means 135. Such variations in the local surface profile of central lumen 130 can have a detrimental effect when catheter apparatus 100 is used for hemodialysis applications.

In accordance with the present invention, central lumen 130 of catheter apparatus 100 is formed smooth enough so that catheter apparatus 100 may be used for hemodialysis applications with good results.

In other words, central lumen 130 of catheter apparatus 100 is formed smooth enough to (1) substantially provide the laminar blood flows required for high volume blood transfer, (2) substantially avoid the creation of irregular blood currents and the creation of blood stagnation areas, (3) substantially avoid the creation of blood clots, (4) substantially eliminate breeding areas for bacteria, and (5) facilitate flush-cleaning of catheter apparatus 100 after dialysis has taken place.

In one particular aspect of the present invention, Applicants have discovered that the cumulative effects of variations in the local surface profile of central lumen 130 can have a significant detrimental effect on the utility of that lumen for hemodialysis applications.

Applicants have further discovered that good hemodialysis results can be achieved if variations in the local surface profile of central lumen 130 average less than about 0.0015 inch and preferably less than about 0.0005 inch (as measured between adjacent occurrences of reinforcing means 135) along the length of central lumen 130. In other words, if catheter apparatus 100 is constructed with a 20 turn helical element, there will be 19 local variation measuring points along any path of measurement taken parallel to the axis of the apparatus. The measurements at these measuring points are then averaged, whereby to provide an average variation in the local surface profile of central lumen 130. Applicants have determined that good hemodialysis results can be achieved where the average variation in the local surface profile of central lumen 130 is less than about 0.0015 inch, and preferably less than about 0.0005 inch.

Thus, in one preferred form of the invention, catheter apparatus 100 is formed so that the average variation in the local surface profile of central lumen 130 is less than about 0.0015 inch, and preferably less than about 0.0005 inch.

The present invention also includes a novel method for fabricating catheter apparatus 100.

In the preferred embodiment of the invention, the novel catheter apparatus 100 is formed as follows.

First, an elongated molding core 200 is provided (Fig. 11) . Molding core 200 is formed so that it is removable from a structure which will be molded over the core, as will hereinafter be discussed. In one preferred form of the invention, molding core 200 is formed so that it has a reducible transverse cross-section, whereby the molding core is removable from a structure which will be molded over the core, as will hereinafter be discussed. Molding core 200 has a smooth finish so that its outer surface 205 is smooth and free from burrs and other surface irregularities. In one preferred form of the invention, molding core 200 is formed out of a polytetrafluoroethylene (PTFE) extrusion which may have its transverse cross-section reduced by stretching it along its longitudinal axis. Preferably, the PTFE extrusion is formed out of virgin stock which is capable of reducing its diameter by approximately 5-10% when subjected to longitudinal stretching. Preferably, the virgin stock is homogenous, so that stretching occurs relatively evenly over the entire body of the core.

Next, a silicone rubber element, or sleeve, 210 is formed about molding core 200 (Fig. 12) . Preferably, this is done by co-extruding silicone rubber element 210 about the outer surface 205 of molding core 200. Inasmuch as molding core 200 has a smooth outer surface 205, the inner surface 215 of silicone rubber element 210 will therefore also be smooth and free from burrs and other surface irregularities.

Then reinforcing means 135, preferably in the form of coil spring 140, is loaded over silicone rubber element 210 (Fig. 13) . Next, support structure 150 (Figs. 6, 7, and 14) is fit over the distal end of molding core 200 and the distal end of silicone rubber element 210. More particularly, support structure 150 is fit over the distal end of molding core 200 and the distal end of silicone rubber element 210 so that the distal end of silicone rubber element 210 rests in counterbore 165 of support structure 150 and against shoulder 175 of support structure 150, and so that molding core 200 extends out through bore 155 of support structure 150 (Fig. 14) . One or more side openings 220 are then formed in silicone rubber element 210 (Fig. 14), and corresponding molding pins (not shown) are inserted into the one or more side openings 220.

Next, a silicone rubber overlayer 225 is molded over reinforcing means 135 (e.g., coil spring 140) and silicone rubber element 210 (Fig. 15) . Preferably, silicone rubber overlayer 225 is applied so that it is seamlessly integrated with silicone rubber element 210. Silicone rubber overlayer 225 may be applied by compression molding or by extrusion (including both intermittent and continuous extrusion) . Preferably, the distal end surface 230 of silicone rubber overlayer 225 is aligned with the distal end surface 160 of support structure 150. The aforementioned molding pins (not shown) located in the one or more side openings 220 extend out through silicone rubber overlayer 225.

Once this has been done, molding core 200 is removed.

In one preferred form of the invention, where molding core 200 has a reducible transverse cross-section, the molding core first has its transverse cross-section reduced, causing it to separate away from the inside wall 215 of silicone rubber element 210 (Fig. 16) . Then molding core 200 is removed.

And in one preferred form of the invention, where molding core 200 is formed out of a PTFE extrusion such that stretching the core extrusion longitudinally will cause it to reduce in diameter, molding core 200 is first stretched longitudinally, causing the molding core to separate away from the inside wall 215 of silicone rubber element 210 (Fig. 16) . Then molding core 200 is removed (Fig. 17) .

After molding core 200 has been removed, the aforementioned molding pins located in the one or more side openings 220 are withdrawn, thereby yielding the finished catheter apparatus 100. Alternatively, the molding pins located in the one or more side openings 220 may be withdrawn prior to removing molding core 200.

In one preferred form of the invention, silicone rubber element 210 and silicone rubber overlayer 225 are both formed out of 80 durometer silicone rubber; silicone rubber element 210 has a wall thickness of approximately 0.005 inch; and silicone rubber overlayer 225 has a wall thickness (between adjacent occurrences of reinforcing means 135) of approximately 0.010 inch.

It is to be appreciated that, when fabricating catheter apparatus 100 by means of the foregoing process, silicone rubber element 210 and silicone rubber overlayer 225 together form the side wall 110 of catheter apparatus 100. Furthermore, inasmuch as molding core 200 has a smooth outer surface 205, the inside wall 215 of silicone rubber element 210 (which inside wall 215 defines the central lumen 130 of catheter apparatus 100) also has a smooth profile.

It has been found that, by forming catheter apparatus 100 by means of the foregoing process, the central lumen 130 of that apparatus will have an interior surface which is sufficiently smooth that blood can be passed through that lumen during a hemodialysis session with good results.

Among other things, it has been found that, by forming catheter apparatus 100 by means of the foregoing process, the average variation in the local surface profile of central lumen 130 will be less than about 0.0015 inch, and preferably less than about 0.0005 inch.

Two of the catheter apparatus 100 can be attached together in ways well known in the art so as to form a complete dual-lumen catheter element 15.

This complete dual-lumen catheter element 15 can then be combined with the connector portion 20 of a percutaneous catheter assembly so as to form a complete percutaneous catheter assembly such as is schematically shown in Figs. 1 and 2. Such a percutaneous catheter assembly may then be used in the hemodialysis of a patient.

Alternatively, the novel complete dual-lumen catheter element 15 can be combined with the connector portion 84 of a subcutaneous port and catheter assembly so as to form a complete subcutaneous port and catheter assembly such as is schematically shown in Figs. 3-5. Such a subcutaneous port and catheter assembly may then be used in the hemodialysis of a patient.

In practice, it has been found possible to provide a dual-lumen catheter element 15, formed out of two of the catheter apparatus 100, which is flexible; capable of substantial bending (e.g., capable of being bent so as to enter the patient's internal jugular vein) without kinking, and resistant to collapse when subjected to substantial negative pressures (e.g., 500 mm of mercury negative pressure.)

It should be appreciated that a dual-lumen catheter element 15 formed out of two of the catheter apparatus 100 is easily "field trimmable" to the desired length. In particular, in one preferred trimming method, a scalpel or the like is first used to cut through side wall 110 and expose reinforcing means 135, and then surgical scissors or the like are used to cut through reinforcing means 135. Alternatively, surgical scissors could be used to cut completely through catheter apparatus 100 in a single step. Numerous modifications can be made to the apparatus and method described above without departing from the scope of the present invention.

Thus, for example, it is also possible to form a dual-lumen catheter element 15 out of one of the aforementioned coil-reinforced catheter apparatus 100 and a conventional, non-coil-reinforced catheter apparatus .

And reinforcing means 135 might be formed out of stainless steel, or a hard plastic, or some other material which is harder than the material used to form tube 105.

Or molding core 200 might be formed out of a material other than PTFE, where the alternative material is also capable of having its transverse cross-section reduced by longitudinal stretching. Or molding core 200 might have its transverse cross-section reduced by a method other than stretching, e.g., depending on the material involved, the molding core might be melted out or dissolved away so as to separate it from silicone rubber element 210. Furthermore, molding core 200 might be removed from within the molded structure by a technique other than reducing its transverse cross-section. By way of example but not limitation, molding core 200 might comprise a sufficiently lubricious material such that the molding core could be removed from within the molded structure by simply pulling the molding core longitudinally out of the molded structure. Or molding core 200 could be blown out of the molded structure.

Also, if desired, the distal end of catheter apparatus 100 can be formed with an alternative geometry.

By way of example but not limitation, a support structure 180 (Figs. 18 and 19) can be utilized, wherein support structure 180 is substantially identical to the support structure 150 discussed above, except that side slots 182 are formed in support structure 180, and appropriate molding pins (not shown) are used in association with side slots 180 to form semi-circular side openings 184 (Fig. 18) in the distal end of the catheter apparatus.

Or, as seen in Fig. 20, side windows 186 can be formed in a support structure 188 which, when covered with appropriate molding pins (not shown) during molding, will yield appropriate openings in the distal end of the catheter apparatus.

Or a simple ring-shaped support structure 190 (Fig. 21) can be used, with or without side openings 145 (Fig. 6) . With such a construction, support structure 190 can be positioned so that its distal end surface 192 resides flush with distal end wall 115 of tube 105, in a manner generally analogous to the construction shown in Fig. 6; or support structure 190 can be encapsulated within the distal end of tube 105, in the manner shown in Fig. 22.

It is also possible for the distal support structure to be attached onto a surface of side wall 110 of tube 105, rather than embedded into the material of side wall 110.

And the distal support structure may open on the distal end of tube 105, and/or open on the inner lumen of tube 105, and/or open on the outer lumen of tube 105.

Or the distal support structure may be omitted completely from the catheter apparatus if desired.

Furthermore, side openings 145 might comprise relatively narrow, longitudinally-extending slits rather than holes, in which case they could act something like a check valve, opening under positive internal pressure but otherwise remaining substantially closed. See, for example, Fig. 22A, which shows side openings 145 in the form of such relatively narrow, longitudinally extending slits, with the slits being shown in their closed position in solid line and in their open position in dashed, or phantom, line.

It should also be appreciated that reinforcing means 135 may take a form other than the coil spring 140 discussed above. For example, reinforcing means 135 might take the form of a plurality of ring-like elements 194, such as is shown in Fig. 23. Alternatively, reinforcing means 135 might comprise a tubular, braided mesh reinforcer. See, for example, Fig. 23A, where reinforcing means 135 are shown, schematically, in the form of a tubular, braided mesh reinforcer 195.

It should also be appreciated that one might form a catheter apparatus of the sort generally described above, including a distal support structure, but omitting reinforcing means 135. It should also be appreciated that, depending on where catheter apparatus 100 is disposed in the patient's body, the distal end of the catheter apparatus may come into contact with adjacent tissue. More particularly, where catheter apparatus 100 is being used to remove "dirty" blood from the body of the patient, the suction created at the distal end of catheter apparatus 100 may cause the end of the catheter apparatus to adhere to the adjacent tissue, in much the same way that a vacuum cleaner nozzle will adhere to the cushion of a couch. See, for example, Fig. 24, where the distal end 115 of catheter apparatus 100 is shown directly engaging the side wall 305 of tissue 300. In this situation, the suction created between the distal end 115 of catheter apparatus 100 and tissue 300 may prevent blood from entering the distal end of catheter apparatus 100 and may prevent catheter apparatus 100 from disengaging itself from tissue 300. This situation can be disastrous in a hemodialysis application.

To the extent that catheter apparatus 100 includes side openings 145 (see Fig. 6) or a support structure having a side opening (e.g., the support structure 180 shown in Figs. 18 and 19 and having a side opening 184), and to the extent such side openings are large enough, sufficient fluid may flow through such alternative openings to prevent a vacuum effect from binding the distal end of catheter apparatus 100 to tissue 300.

Alternatively, and looking now at Fig. 25, one or more notches 400 may be provided in the side wall of catheter apparatus 100 to permit blood to enter through the side wall of the catheter apparatus and thereby prevent vacuum binding. Notches 400 preferably open on the distal end 115 of catheter apparatus 100 and extend completely through the side wall of the catheter apparatus. Notches 400 collectively have a surface area large enough to prevent a vacuum effect if the distal end of catheter 100 contacts tissue 300. In one preferred form of the invention, the one or more notches 400 have a collective surface area substantially no less than the surface area of the catheter's lumen. In one preferred form of the invention, notches 400 preferably have a length no greater than about twice the diameter of the catheter. This is because the presence of the notches prevents a good anticoagulant lock from being established in the catheter all the way down to the distal tip, since the anticoagulant can leak put through the notches and be replaced by blood. As a result, a resident clot will typically form in the catheter at the conclusion of the dialysis session, which clot must be flushed out at the start of the next dialysis session. Thus, by limiting the length of notches 400, one can also limit the length of the resident clot.

Figs. 26-29 illustrate some alternative tip constructions. Fig. 26 shows a tip having a "triangle notch" construction. Figs. 27A and 27B show a "forked tip" construction. Figs. 28 and 29 show an "angle cut" construction, with Fig. 29 also showing a side opening 145.

As noted above, reinforcing means 135 are intended to strengthen the side wall 110 of catheter apparatus 100 so that the side wall can be made as thin as possible without compromising the integrity of side wall 110. This generally means that reinforcing means 135 must be relatively thin as well. Unfortunately, however, such thinness can result in the reinforcing means becoming easily damaged during assembly of the catheter apparatus, or during deployment of the catheter apparatus, or during use of the catheter apparatus .

By way of example, where catheter apparatus 100 has an outer diameter of 0.135 inch and an inner diameter of 0.105 inch, and reinforcing means 135 comprise a titanium coil spring having a thickness of approximately 0.006 inch and a coil rate of approximately 0.031-0.038 pitch, care must be taken so that the titanium coil spring is not excessively stressed during the assembly, deployment or use of the catheter apparatus. In particular, if the titanium coil spring is excessively stressed, it can become deformed and take on a set in its deformed condition, such that the catheter lumen will be restricted.

For example, such titanium coil springs must be handled carefully during manufacturing operations so as to prevent damaging the coil springs. This can be a problem, particularly inasmuch as such springs typically exceed two (2) feet in length and undergo repeated handling. Also, significant care must be taken during deployment of the catheter apparatus. For example, if medical personnel apply a clamp to the catheter apparatus during deployment, the clamp may crush the coil spring, causing it to take on a set, such that the catheter's lumen will be restricted. Also, if oversized scissors are used to trim the catheter apparatus to length during deployment of the catheter, the spring coils adjacent to the cutting location may be crushed. And during use, medical personnel must be careful not to place clamps over the catheter apparatus, since this may also cause the coil spring to take on a set. Furthermore, patients must be careful to avoid any activities or movements which could result in the catheter apparatus being crushed.

It has been discovered that these problems can be overcome by forming reinforcing means 135 out of a so-called "superelastic" material, e.g., a nickel-titanium alloy such as Nitinol. Such materials are sometimes also known as "stress-induced martensite, shape memory alloys" ("SIM-SMA") . By forming reinforcing means 135 out of such highly elastic materials, the assembly, deployment and use of the catheter apparatus is greatly facilitated, since the reinforcing means are able to elastically undergo a very wide range of stresses without taking on a set. It is also possible for tube 105 to be formed out of a material other than silicone rubber. By way of example but not limitation, tube 105 might be formed out of a similar elastomeric or plastic material such as urethane, or polyvinylchloride (PVS), or the like.

Referring next to Figs. 30-43, it will be seen that there is presented an inventive method for producing another novel and unique elastomeric catheter tube. More particularly, in Figs. 36 and 43 there is shown a novel tubular member 500 which includes a first lumen 502, the side walls of which are reinforced by a coil spring 504, as above described, and a second lumen 506, the side walls 508 of which are collapsible when the lumen 506 is not internally pressurized.

In one preferred method for producing the tubular member 500, a first lumen core 510 (Figs. 30 and 37), which may be of PTFE or the like, is covered by a sleeve 512 (Figs. 31 and 38) of silicone rubber or the like. The first lumen core 510 and sleeve 512 may be formed substantially simultaneously by coextrusion. The coil 504 (Figs. 32 and 39) is then mounted on the sleeve 512, as described above. Referring next to Figs. 33, 40, 44, 45 and 84, it will be seen that a second lumen mandrel 514 is positioned adjacent the coil 504 and alongside the first lumen core 510. A final layer 516 (Figs. 34-36 and 41-43) of silicone rubber or the like is formed by a mold 518 (Figs. 40 and 44). The final, or outer, layer 516 forms the second lumen 506 in a collapsed and expandable state (Figs. 41-43) .

After forming the outer layer 516, the second lumen mandrel 514 and the first lumen core 510 are removed (Figs. 35, 36 and 85) . As discussed hereinabove, the core 510 may be stretchable, such that by pulling opposite ends thereof, as shown in Fig. 35, the diameter of the core is reduced, thereby facilitating removal of core 510 from the tubular member 500.

The first lumen 502 is preferably the suction lumen, and the second lumen 506 is preferably the return lumen. When tubular member 500 is not in active use, no blood is returned through the second lumen 506 and the second lumen is in its collapsed state (Fig. 85) . The first lumen 502 is maintained in an open condition by the coil 504, or other reinforcing means, and therefore requires a relatively thin side wall. Thus, in the inactive condition, one lumen of thin- walled construction is open, and the other lumen is collapsed, providing a minimal profile in the passageway in which the catheter is disposed and permitting blood flow closer to normal than is the case with two open tubes.

In Figs. 46-65 there is shown an alternative series of steps for producing the tubular member 500. As in the immediately previous embodiment, in the alternative method the first lumen core 510 (Figs. 46 and 56) is covered by the sleeve 512 (Figs. 47 and 57), and then coil 504 is loaded over sleeve 512 (Figs. 48 and 58) . A preliminary second lumen mandrel 520 (Figs. 49 and 59) is positioned adjacent to the coil 504 and alongside the first lumen core 510. The outer layer 516 (Figs. 50 and 60) of silicone rubber is then molded around the assembly. The preliminary lumen mandrel 520 is then removed (Fig. 51) and a lumen forming core 522 (Figs. 52 and 62) is inserted in the tunnel 524 (Fig. 62) left by removal of the preliminary lumen mandrel 520. A forming mandrel 526 (Figs. 53 and 63) is then brought to bear against the second lumen side walls 508 (Fig. 63) to form the side wall 508 in the collapsed and expandable configuration shown in Fig. 64, and the lumen forming core 522 is withdrawn (Fig. 54), and then first lumen core 510 stretched (Fig. 54) and withdrawn (Fig. 55), leaving the formed dual-lumen tubular number 500 (Fig. 65) . Again, tubular member 500 includes a first lumen 502 defined by a relatively thin wall incorporating coil 504 to keep it open, and a normally-collapsed second lumen 506 which will be opened by internal pressure during an active dialysis session.

A further alternative method for forming the tubular member 500 is illustrated in Figs. 66-83. As in the two immediately previous methods, in this alternative method the first lumen core 510 (Figs. 66 and 75) is covered with the sleeve 512 (Figs. 67 and 76), and the coil 504 is mounted thereon (Figs. 68 and 77) . The second lumen mandrel 514 is positioned adjacent to the coil 504 and parallel with the first lumen core 510 (Figs. 69.and 78), and then the outer layer 516 of elastomeric material is molded on and around the assembly shown in Figs. 69 and 78 so as to produce the assembly shown in Figs. 70 and 79. The second lumen mandrel 514 is then withdrawn (Fig. 71), leaving an open second lumen 506 (Fig. 81) .

A lumen tool 528 (Fig. 81), which may be a weighted and/or heated member, is then brought to bear against the tubular member 500 in the area of the second lumen 506 so as to press the side wall of the second lumen into the compressed but expandable condition shown in Fig. 82. The lumen tool 528 is then withdrawn, and the first lumen core 510 is stretched (Fig. 73) and withdrawn (Fig. 74), leaving the tubular member 500 with the first lumen 502 open and reinforced, and the second lumen 506 collapsed but capable of expansion when internally pressurized.

Referring next to Figs. 86-89, it will be seen that alternative cross-sectional configurations of tubular members 500 may be produced. Coils 504 of a "D" shape (Figs. 86 and 87) and of an elliptical shape (Figs. 88 and 89) may be provided, in addition to the circular coils of Figs. 84 and 85. In this respect it will be appreciated that when catheter 500 is in a non-active condition (i.e., when the second lumen 506 is collapsed) , the member 500 with a D shape coil or an elliptical shape coil assumes a round, or nearly round, cross-section (Figs. 87 and 89, respectively), whereas when the coil 504 is round, even in collapsed condition, the tubular member 500 is of an oblong cross-section (Fig. 85) .

In the foregoing description and associated drawings, the two mouths of the dual-lumen catheter (i.e., the mouth of the suction line and the mouth of the return line) are shown as terminating next to one another (see, for example, Fig. 2) . However, it is also possible for the one of the mouths to terminate distally of the other mouth. For example, the return line may terminate distally of the suction line (see, for example, Figs. 90-94), or for the suction line to terminate distally of the return line (see, for example, Figs. 95-97) .

In Figs. 90 and 93, there is shown an embodiment of tubular member 500 in which the distal end of the first lumen 502, or suction lumen, is proximally well removed from the distal end of the second, or return, lumen 506. Such an arrangement can be preferred where the dual-lumen catheter is disposed in the superior vena cava, since it generally reduces the possibility that "clean" blood exiting the return lumen 506 will be captured by suction lumen 502. A wall 530 (Fig. 90) of the second lumen 506 is preferably dished so as to form a trough 532 which serves as a sort of guide channel for blood, the channel extending toward, and up to, the first lumen distal opening 534. In this embodiment, the reinforcing coil 504 supports the wall of the first lumen 502.

In Fig. 91, there is shown another embodiment in which the open distal end of the first lumen 502 is elongated so as to provide a first lumen distal opening 534 which is also elongated and presents an increased area for taking in blood.

In Figs. 92 and 94, there is shown a similar embodiment in which the reinforcing coil 504 includes a first lumen distal opening reinforcing portion 536 (Fig. 92) by extending around the distal opening 534. Further, the coil includes a distal extended portion 538 which is encased in the side wall of the second lumen 506 and serves to longitudinally support the second lumen 506, while still permitting that second lumen 506 to assume its collapsed position when the catheter is not being used in an active dialysis session. As noted above, it is also possible to form the dual-lumen catheter so that the suction line terminates distally of the return line (see, for example, Figs. 95-97) . With such a construction, it may be desirable, where the dual-lumen catheter is to be deployed in the superior vena cava, to add a flow diverter 603 just distal to the return line 605, whereby to reduce the possibility that "clean" blood exiting return line 605 will be drawn into suction line 607.

Of course, it should also be appreciated it is possible to make a dual-lumen catheter of the sort shown in Figs. 95-97 with, or without, an interior reinforcing coil, and with, or without, a collapsible lumen.

It is also possible to provide a dual lumen catheter having a single reinforcing coil surrounding the two lumens. More particularly, and looking now at Fig. 98, there is shown a catheter 700 having a pair of lumens 702, 704, with the two lumens being surrounded by a single reinforcing coil 706.

It will, of course, be appreciated that various other modifications may be made to the embodiments disclosed above without departing from the spirit and scope of the present invention. Accordingly, it is intended that this invention be limited only by the claims ultimately issued from this patent application and/or from any patent application (s) claiming priority therefrom.

Advantages Of The Invention

Numerous advantages are achieved through the provision and use of the present invention.

For one thing, the present invention provides improved apparatus for use in the dialysis of blood.

And the present invention provides an improved catheter element for use in the dialysis of blood, wherein the catheter element may be used in either a percutaneous catheter assembly or a subcutaneous port and catheter assembly.

Also, the present invention provides an improved catheter element which has the largest possible interior diameter and the smallest possible exterior diameter, yet is resistant to bursting, collapse and kinking.

And the present invention provides an improved catheter element which incorporates reinforcing means within the side wall of the catheter, yet has an interior lumen which is sufficiently smooth that the catheter element may be used in hemodialysis applications with good results.

The present invention also provides a support structure at the distal end of the catheter element to help maintain openness of the flow path through the catheter element.

And the present invention provides an improved catheter element having an improved tip geometry so as to help maintain openness of the flow path through the catheter element.

Furthermore, the present invention provides an improved method for fabricating apparatus for use in the dialysis of blood.

And the present invention provides an improved method for the dialysis of blood.

The present invention further provides a single tubular member having a suction lumen of thin walled but strong and durable construction, and a return lumen collapsible when not in active use, to exhibit a minimal cross-section profile in the vein or artery in which the tubular member is disposed. The present invention further provides a method for fabricating the dual-lumen tubular member, and a method for the dialysis of blood utilizing the new dual-lumen tubular member.

Still other advantages associated with the present invention will be obvious to a person skilled in the art.

Claims

What Is Claimed Is:

1. A catheter comprising an elongated flexible tubular element defining first and second lumens extending therethrough end to end, said member being formed of a biocompatible material, a reinforcing structure encased by said material and reinforcing side walls of only said first lumen, said second lumen being defined by side walls collapsible when said second lumen is devoid of internal pressurization.

2. A catheter according to claim 1 wherein the average variation in the local surface profile of said lumens is less than about 0.0015 inch.

3. A catheter according to claim 1 wherein said biocompatible material comprises silicone rubber.

4. A catheter according to claim 3 wherein said biocompatible material comprises silicone rubber having a hardness of approximately 80 durometer.

5. A catheter according to claim 1 wherein said reinforcing structure is of a superelastic material stiffer than the biocompatible material.

6. A catheter according to claim 5 wherein said reinforcing structure is formed out of a nickel-titanium alloy.

7. A catheter according to claim 1 wherein said reinforcing structure comprises a coil.

8. A catheter according to claim 7 wherein the wire forming said coil has a thickness of approximately 0.006 inch and a coil rate of approximately 0.031-0.038 pitch.

9. A catheter according to claim 7 wherein said coil comprises nickel-titanium alloy.

10. A catheter according to claim 9 wherein the wire forming said coil has a thickness of approximately 0.006 inch and a coil rate of approximately 0.031-0.038 pitch.

11. A catheter according to claim 1 wherein said reinforcing structure comprises a plurality of ring-like elements.

12. A catheter according to claim 1 wherein at least a portion of said first lumen side wall has a thickness of approximately 0.015 inch.

13. A catheter according to claim 1 wherein said tubular element is provided with a smooth outer surface.

14. A catheter according to claim 1 further comprising a support structure attached to said first lumen side wall adjacent to said open distal end of a first lumen portion of said flexible tubular member.

15. A catheter according to claim 14 wherein said support structure is at least partially embedded in said first lumen side wall.

16. A catheter according to claim 14 wherein said support structure is formed of a radio-opaque material.

17. A catheter according to claim 14 wherein said first lumen is substantially cylindrical, and further wherein said support structure comprises a circular element formed of a material more rigid than the biocompatible material forming said at least one tubular member.

18. A catheter according to claim 1 wherein said first lumen side wall defines an opening in proximally-spaced, proximate relation to an open distal end of said first lumen.

19. A catheter according to claim 18 wherein said first lumen opening is substantially circular.

20. A catheter according to claim 18 wherein said first lumen opening comprises a longitudinally-extending notch.

21. A catheter according to claim 20 wherein the first lumen side wall defining said notch is at least partially rounded.

22. A catheter according to claim 20 wherein the first lumen side wall defining said notch is at least partially straight.

23. A catheter according to claim 20 wherein said notch is N-shaped .

24. A catheter according to claim 20 wherein said notch has a length no greater than about twice the diameter of the first lumen.

25. A catheter according to claim 1 wherein a distal end of said tubular element is formed with a forked tip configuration.

26. A catheter according to claim 1 wherein a distal end of said tubular member extends at an acute angle to a longitudinal axis of an adjacent portion of said tubular member.

27. A catheter according to claim 1 wherein said first lumen is of a round configuration in cross-section and said second lumen is defined by a first wall portion concentric with said first lumen, and said side walls overlying said first wall portion and joined thereto to define said second lumen.

28. A catheter according to claim 1 wherein said first lumen is elliptically shaped in cross-section and said second lumen is defined by an elliptic first wall portion adjacent to said first lumen, and said side walls overlying said first wall portion and joined thereto to define said second lumen.

29. A catheter according to claim 1 wherein said first lumen is D-shaped in cross-section and said second lumen is defined by a first substantially straight wall adjacent to a straight wall of said first lumen, and said side walls overlying said second lumen straight wall and joined thereto to define said second lumen.

30. A catheter according to claim 1 wherein said reinforcing structure comprise a tubular, braided mesh.

31. A catheter according to claim 1 wherein the biocompatible material comprises a material selected from a group of materials consisting of urethane and polyvinylchloride .

32. A catheter according to claim 31 wherein the biocompatible material is radio-opaque.

33. A catheter according to claim 1 wherein said reinforcing structure comprises a wire structure and a portion of said wire structure extends to and at least partially around a distal open end of said first lumen to support said distal end in an open condition.

34. A catheter according to claim 1 wherein said first lumen comprises a suction lumen for removing blood from a patient's vascular system, and said second lumen comprises a return lumen for returning blood to the patient's vascular system, a distal end of said first lumen being proximal to a distal end of said second lumen, said reinforcing structure comprising a wire coil disposed around said first lumen along the length of said first lumen, a portion of said wire extending around said distal end of said first lumen to support said first lumen distal end in an open condition.

35. A catheter according to claim 34 wherein said wire further extends distally from said first lumen distal end towards said second lumen distal end within a wall of said second lumen to longitudinally stabilize said second lumen.

36. The catheter according to claim 34 wherein said wall of said second lumen is in alignment with said distal end of said first lumen and is trough-shaped so as to guide blood into said first lumen distal end.

37. Apparatus for use in the dialysis of the blood of a patient, said apparatus comprising a connector portion and a catheter portion; said connector portion comprising an outlet adapted for communication with a line connected to an input port of a dialysis machine, and an inlet adapted for communication with a line connected to an output port of a dialysis machine; and said catheter portion comprising a catheter member comprising: an elongated flexible tubular member defining first and second lumens extending therethrough end to end, said member being formed of a biocompatible material, a reinforcing structure encased by said material and reinforcing side walls of only said first lumen, said second lumen being defined by side walls collapsible when said second lumen is devoid of internal pressurization, said first and second lumens each having an interior surface sufficiently smooth for use in hemodialysis applications; a proximal end of a first lumen portion of said tubular member being connected to said connector portion and in communication with said outlet, and a distal end of said first lumen portion of said tubular member terminating in a suction line mouth; a proximal end of a second lumen portion of said tubular element being connected to said connector portion and in communication with said inlet, and a distal end of said second lumen portion of said tubular member terminating in a return line mouth; said tubular member being adapted for disposition within the body of the patient so that said suction line mouth and said return line mouth are both disposed in the vascular system of the patient.

38. Apparatus according to claim 37 wherein said connector portion comprises an extracorporeal connector element adapted for attachment to an outside surface of the body of the patient.

39. Apparatus according to claim 37 wherein said connector portion comprises a subcutaneous element adapted for implantation within the body of the patient.

40. A method for making a catheter, said method comprising the steps of:

(a) providing an elongated molding core; (b) forming a sleeve of biocompatible material on said molding core;

(c) positioning reinforcing structure on an outer surface of said sleeve;

(d) positioning a lumen mandrel adjacent said reinforcing structure and extending alongside said molding core;

(e) forming an overlayer of biocompatible material over said sleeve, said reinforcing structure, and said lumen mandrel, and

(f) removing said lumen mandrel to provide a lumen and removing said molding core to provide a further lumen.

41. A method according to claim 40 wherein said reinforcing structure is of a superelastic material.

42. A method according to claim 40 wherein said molding core is stretchable, and including the step of stretching said molding core prior to removal thereof from the tubular member.

43. A method for making a catheter, said method comprising the steps of:

(a) providing an elongated molding core;

(b) forming a sleeve of biocompatible material on said molding core, said sleeve defining a first lumen therethrough;

(c) positioning reinforcing structure on an outer surface of said sleeve;

(f) removing said lumen mandrel from the overlayer;

(g) inserting a forming core in the opening in said overlayer formed by said lumen mandrel;

(h) engaging said overlayer adjacent said forming core with a forming mandrel so as to form, between the forming core and the forming mandrel, a second lumen in a collapsed and expandable state; (i) removing said forming core to provide said second lumen in said catheter; and

(j) removing said molding core from the tubular member to provide said first lumen in said catheter.

44. A method according to claim 43 wherein said reinforcing structure is of a superelastic material.

45. A method according to claim 43 wherein at least one of said molding core and said lumen mandrel is stretchable, and including the step of stretching said at least one of said molding core and said lumen mandrel prior to removal thereof from the tubular member.

46. A method according to claim 43 wherein said overlayer is formed by compression molding.

47. A method according to claim 43 wherein said overlayer is formed by extrusion.

48. A method for making a catheter, said method comprising the steps of: (a) providing an elongated molding core;

(b) forming a sleeve of biocompatible material on said molding core;

(c) positioning reinforcing structure on an outer surface of said sleeve;

(e) forming an overlayer of biocompatible material over said sleeve, said reinforcing structure, and said lumen mandrel;

(f) removing said lumen mandrel to provide an opening through said catheter;

(g) applying a form tool to said overlayer adjacent to said tunnel so as to provide a lumen in a collapsed and expandable state; and

(h) removing said molding core so as to provide a further lumen.

49. A method according to claim 48 wherein said reinforcing material comprises a superelastic material.

50. A method according to claim 48 wherein said molding core is stretchable, and including the step of stretching said molding core prior to removal thereof from the tubular element.

51. A method for the dialysis of the blood of a patient, said method comprising the steps of:

(a) providing a dialysis machine, and providing apparatus comprising a connector portion and a catheter portion; said connector portion comprising an outlet adapted for communication with a line connected to an input port of said dialysis machine, and an inlet adapted for communication with a line connected to an output port of said dialysis machine; and said catheter portion comprising a catheter element comprising: a suction lumen and a return lumen, each of said lumens being disposed in a single flexible tubular member, said tubular member having side walls defining said suction and return lumens, said side walls (1) being formed of a biocompatible material, (2) encasing a reinforcing structure therein for reinforcing portions of said side walls surrounding only said suction lumen, and (3) having smooth interior surfaces for defining said lumens, said smooth interior surfaces being sufficiently smooth for use in hemodialysis applications; a proximal end of said suction lumen being connected to said connector portion and in communication with said outlet, and a distal end of said suction lumen terminating in a suction lumen mouth; a proximal end of said return lumen being connected to said connector portion and in communication with said inlet, and a distal end of said return lumen terminating in a return lumen mouth; said suction lumen and said return lumen being adapted for disposition within the body of the patient so that said suction lumen mouth and said return lumen mouth are both disposed in the vascular system of the patient;

(b) placing said lumen mouths in the vascular system of the patient;

(c) connecting said connector outlet to the input port of said dialysis machine, and connecting said connector inlet to the output port of said dialysis machine; and

(d) operating said dialysis machine.

52. A method according to claim 51 wherein said connector portion comprises an extracorporeal connector element attached to an outside surface of the body of the patient.

53. A method according to claim 51 wherein said connector portion comprises a subcutaneous element implanted within the body of the patient.

54. A method according to claim 51 wherein said suction and return lumen portions of said tubular member are field trimmed to size prior to being connected to said connector portion.

55. A method according to claim 54 wherein said reinforcing structure is of a superelastic material and does not take a set even when deformed during field trimming of said lumen portions of said tubular element.

56. A method according to claim 54 wherein said suction and return lumen portions of said tubular member are field trimmed to size using surgical scissors prior to being connected to said connector portion.

57. A catheter according to claim 1 wherein said first and second lumens each having an interior surface sufficiently smooth for use in hemodialysis applications.

58. A catheter according to claim 7 wherein said reinforcing structure comprises a helix.

59. A catheter according to claim 1 wherein said elongated flexible tubular element comprises an additive so as to render some or all of said elongated flexible tubular element radio-opaque.

60. A catheter according to claim 34 wherein said wire is radio-opaque.

61. A catheter comprising an elongated flexible tubular element defining a lumen extending therethrough end to end, said member being formed of a biocompatible material, and a reinforcing structure encased by said material and reinforcing side walls of said lumen, said reinforcing structure having a variable density along its length.

62. A catheter according to claim 61, wherein said reinforcing structure comprises a coil, and further wherein the pitch of said coil decreases at one or more locations along its length.

63. A catheter according to claim 61 wherein the pitch of said coil decreases at one end of said coil.

64. A catheter comprising an elongated flexible tubular element defining first and second lumens extending therethrough end to end, said member being formed of a biocompatible material, wherein said first lumen comprises a suction lumen for removing blood from a patient's vascular system, and said second lumen comprises a return lumen for returning blood to the patient's vascular system, a distal end of said first lumen being distal to a distal end of said second lumen, and further wherein a flow diverter is disposed between said distal end of said first lumen and said distal end of said second lumen so as to reduce the possibility that blood exiting said second lumen will be drawn into said first lumen.

65. A catheter according to claim 60 wherein said catheter further comprises a reinforcing structure encased by said material and reinforcing side walls of only said first lumen, said second lumen being defined by side walls collapsible when said second lumen is devoid of internal pressurization.

66. A catheter comprising an elongated flexible tubular element defining first and second lumens extending therethrough end to end, and a single reinforcing coil surrounding said first and second lumens.

67. A catheter according to claim 61 wherein said reinforcing structure comprises a coil, and further wherein said coil comprises multiple layers.