CATHETER AND A NOVEL USE OF A FLEXIBLE TUBE

Abstract: The invention relates to a catheter, particularly a permanently implanted catheter, particularly a peritoneal-dialysis one, particularly for such peritoneal dialysis where a catheter tube is positioned normally to the surface area at the location of implantation, which catheter consists of a flexible catheter tube and at least one cuff, which is stable in its position on the catheter tube. The catheter tube provides a length segment (A) beginning next to the patient's skin, the general flexibility of the said length segment being greater than that of the remaining length section of the catheter, so that the catheter tube protruding from the patient's abdomen easily bends at the said length segment without collapsing (being squeezed). In a basic embodiment of the invention, the length segment (A) of the catheter consists of a main tube (1) and two mantle tubes (2, 3) fitted individually onto each length section of the said main tube so that a spacing exists between them, whose length corresponds to the said length segment (A), with reinforcing rings (4) being arranged on the main tube (1) in the region of the said length segment (A). The invention foresees several variant embodiments. Further, the invention relates to a novel use of a flexible tube as means for providing a length segment, whose flexibility in comparison to that of the remaining length section(s) of a tube assembly is intentionally accentuated.

Description: CATHETER AND A NOVEL USE OF A FLEXIBLE TUBE Int. CL: A 61 M 1/28 Dialysis systems; peritoneal dialysis A 61 M 5/14 Devices for bringing media into the body in a subcutaneous, intra- vascular or intramuscular way; infusion devices, e.g. infusing by gravity A 61 M 25/01 Catheters, particularly introducing, guiding, advancing, emplacing or holding thereof B 65 G 53/54 Use of flexible pipes or tubes The invention concerns a catheter, particularly a permanently implanted catheter, especially a peritoneal-dialysis one, particularly for such peritoneal dialysis where a catheter tube is positioned normally to the surface area at the location of implanta¬ tion. The invention also concerns a novel use of a flexible tube. The peritoneal dialysis, the approach thereto, the surgical implantation of a peritoneal catheter as well as catheter-related complications such as infections of the catheter exit site and of the subcutaneous tunnel are clearly and systematically analyzed in Peritoneal Dialysis, ed. Karl D. Nolph, Kluwer Academic Publishers (1989), Dordrecht, The Netherlands. Since the present application is drafted for those skilled in the art (manufacturers of catheters and physicians), the descriptions of peritoneal dialysis as such and of the catheters, all being described in the said reference, as well as of materials ap¬ propriate to be used for this and other purposes have been omitted. Of decisive importance for the beginning of inventive activity was the authors' state¬ ment in the above reference that the use of a catheter, which in the case of peritoneal dialysis is practically permanently implanted into the patient, is accompanied i.a. by frequent inflammations of the subcutaneous tunnel, particularly the sinus tract thereof i.e. the section of the subcutaneous tunnel between the catheter entry/exit site and the nearest subcutaneous cuff, and of the entry/exit site itself, by the leaking of the dialysis fluid from the abdominal cavity along the outer mantle surface of the catheter, which particularly occurs with single-cuff catheters, and even by peritonitis. A basic object of the invention was, therefore, to provide measures for protecting the patients from the said inflammations. One line of investigating the causes of inflam¬ mations was based on the supposition that the apparatus involved in the peritoneal- dialysis system was faultless. However, in spite of eliminating the possible subjective causes of infections one after the other, inflammations occurred. It turned out that the infections were mainly caused by the catheter entry/exit site on the patient's ab¬ dominal wall being continually irritated due to practically continuous changing of the position of the outer section of the catheter. Due to the movements of the free end of the catheter, the neighbouring tissue of the patient's abdomen is subjected to stretch¬ ing in all directions with respect to the surface area of the abdomen and, additionally, deformations of the skin in the inward and outward directions as well as spiral wind¬ ings of the skin and of the subcutaneous layer occur. It has been established that in spite of using double-cuff catheters (two cuffs mean two retaining/anchoring locations of the catheter in the patient) and in spite of penetrating the patient's skin by the catheter tube normally to its surface (normal positioning is less stressful for the skin than angular implantation) and in spite of the catheter tube being made of a biocompatible material, which as such is flexible and (from the point of view of the material) not aggressive to the tissue, which all should have been sufficient for ehminating the foreseeable problems, the catheter in use, when its outer free segment is freely moved, evidently behaves substantially as a rigid body in the region of the sinus section of the tunnel; therefore a local irritation of the mouth of the sinus section cannot be excluded. A solution of the above problem based on moving one of the cuffs to the surface of the patient's abdominal wall and arranging it there in a suitable manner in order to secure the entry/exit site of the catheter would generate several new problems. Hence the said solution has not been elaborated on. Finally, the object of the inven¬ tion crystallized as the question how the catheter tube itself should be constructed in order to provide a sufficient flexibility in the region of the entry/exit site in the ab¬ dominal wall to make possible optional movements of the free outer section of the catheter without stressing the tissue and thereby irritating the entry/exit site. Thus, the object of the invention is to embody a catheter with a special length seg¬ ment arranged next to the entry/exit site, whose flexibility will be more distinct than that of the proper catheter tube so that in the course of free movements the said length segment will form a continuous bend without running the risk of collapsing (being squeezed). Proceeding from a catheter, particularly a permanently implanted catheter, espe¬ cially a peritoneal-dialysis one, particularly for such peritoneal dialysis where a catheter tube is positioned normally to the surface area at the location of implanta¬ tion, the catheter consisting of aperse flexible catheter tube and of at least one cuff which, as to the position in the longitudinal direction, is stable on the catheter tube, the above object is achieved by a construction where the catheter tube has a length segment foreseen in the section of the catheter protruding from the patient, with the said length segment beginning next to the patient's skin, the general flexibility of the said length segment being greater than that of the remaining part of the catheter tube protruding from the patient, so that the catheter tube protruding from the patient's abdominal wall easily bends at the said length segment, which results in that the moving of the free part of the catheter generates no substantial irritation of the entry/exit site of the sinus section of the subcutaneous tunnel. The said length segment of the catheter, whose general flexibility is greater than that of the remaining part of the catheter tube protruding from the patient's body, typi¬ cally consists of a main tube having an accentuated smoothness of the inner mantle surface and of two mantle tubes fitted individually onto each end of the said main tube so that a spacing exists between them, whose length corresponds to the said length segment, with reinforcing rings being arranged in a stationary manner on the main tube in the region of the said length segment. The said reinforcing rings are preferably round in section, equal to each other and positioned equidistantly. Alternatively, a spiral element is arranged on the main tube in the region of the said length segment, which element is stationarily held on the main tube or integral with it. The material of the spiral element is typically round in section. In a further alternative embodiment, the main tube is provided with stationary rein¬ forcing rings upon its entire length, with the spacing of the reinforcing rings in the region of the respective length segment being greater than at the remaining end sec¬ tions of the main tube. In a still further alternative embodiment of the catheter, the main tube is provided with stationary reinforcing spiral elements upon its entire length, with the thread (pitch of thread) of the reinforcing spiral element in the region of the respective length segment being greater than that at the remaining spiral elements of the main tube. The spiral elements are bound to the main tube or are integral with it. In an alternative embodiment of the invention, the catheter tube has annular grooves at the respective length segment foreseen to be located next to the patient's skin, the annular grooves weakening the wall of the tube and thereby increasing the flexibility thereof. In an alternative embodiment of the invention, the catheter tube has annular ribs at the respective length segment foreseen to provide increased flexibility. Preferably, the outer diameter of the catheter tube in the respective length segment is smaller than that of the remaining catheter tube. Finally, in a further alternative embodiment of the invention, the respective length segment foreseen to provide increased flexibility is composed of toroid elements con¬ stituting tubular bellows. Alternatively, if feasible in given manufacturing conditions, instead of a series of toroid elements a bulge helix can be foreseen. The invention also relates to a novel use of a flexible tube as a means for providing a length segment, whose flexibility is intentionally accentuated in comparison to that of the remaining section(s) of a tube assembly. At the present invention, in a plastic tube for manufacturing a catheter, particularly one for permanent implantation, especially one for peritoneal dialysis, a length segment having accentuated flexibility is made of a tube assembly composed of a flexible tube with a high-degree smooth¬ ness of the inner mantle surface and of an outer reinforcement designed either as rings or a thread, the tube assembly thus being similar to certain artificial veins. In the continuation, the invention is disclosed in more detail on the basis of several embodiments shown in the attached drawings. The Figs, of the drawings are not made to scale and they only have an informative significance. In each Fig. a catheter in its sectional view is shown, whose inner section, i.e. the sec¬ tion between a cuff and the inner end of the catheter, is omitted in the drawings since it is taken from the prior art and known to anyone skilled in the art. According to the invention, the object of the invention is achieved by several ap¬ proaches. The catheter of Fig. 1 consists of a main catheter tube 1 suitable for manufacturing catheters (i.e. with a high-degree smoothness of the inner mantle surface), whose one end section is fitted with a mantle tube 2 and its other end section is fitted with a mantle tube 3. An appropriately dimensioned length clearance A is provided between the two mantle tubes 2,3, where rings 4 are disposed on the mantle surface of the main tube 1. The rings 4 are suitably spaced equidistantly from each other with the two terminal rings 4 being each spaced from the ends of the mantle tubes 2,3 for a clearance equal to the mutual clearance of rings 4. The rings 4 are preferably cir¬ cular in section and suitably all uniform and bound to the main tube 1 in an ap¬ propriate manner, e.g. glued thereto, so that the stationary state of the rings 4 with respect to the main tube 1 is guaranteed. The sectional area of the rings 4, their mutual clearance and the spacing of the ter¬ minal rings 4 from the ends of the mantle tubes 2,3 are suitably dimensioned under the consideration of the condition that at an extreme bending of the catheter by the length segment A (meaning the case with the catheter implanted normally to the patient's skin, the curving then amounts to approx. 90°), the rings 4 may at most abut against each other along the line of the inner curve. It follows from the said supposi¬ tion that also embodiments with rings of different sectional areas are possible within the metes and bounds of the teachings of this invention, e.g. embodiments with the sectional area of the rings increasing or decreasing from the terminal rings towards the middle of the series of rings, or embodiments with a great sectional-area ring fol¬ lowed by a small sectional-area ring and vice versa. It is possible, in the above man¬ ner, to influence voluntarily the nature of the curve of the length segment A. With one of the embodiments the said curve is arcuate, with another one it is ellipse- shaped, etc. As to the above embodiment it is to be noted that it is probably not necessary to ex¬ tend the main tube 1 of the catheter through the whole length of the mantle tubes 2, 3. If allowed by the manufacturing equipment, the length of the main tube 1 can even be limited to the actual length of the section A with the tube sections 2, 3 - now con¬ stituting two sections of the proper main tube of the catheter - being directly con¬ nected to the former either by abutting or by overlapping. The embodiment shown in Fig. 2 only differs from the above-described one by the use of a spiral element 5 instead of a series of rings 4. Again, the spiral element 5 is made of a circular-section material and fixed as to the position on the tube 1. Material prototypes of the inventive catheters of Figs. 1 and 2 as required for carry¬ ing out practical tests and for verifying the inventive idea, i.e. for testing the flexibility, used a length segment A between two sections of a prior art catheter tube, which segment was made of a commercially available artificial vein of the type com¬ prising a tube element (similar to the tube 1 in the present case) and a ring-shaped mantle reinforcement (similar to the rings 4) or a spiral-element mantle reinforce¬ ment (the spiral element 5), respectively. The embodiments of Figs.3 and 4 evidently differ from those of Figs. 1, 2 in that the mantle tubes 2, 3 of the embodiments of Figs. 1, 2 are not required. The embodiment of Fig. 3 represents a modification of the embodiment of Fig. 1, the modification being based on the substitution of the mantle tubes 2, 3 by a series of rings 4, mutually uniform, with the density of rings 4 being smaller along the length segment A than along the remaining two length sections of the catheter tube. Analogously, the embodiment of Fig.4 is a modification of the embodiment of Fig. 2, the modification being based on the substitution of the mantle tubes 2, 3 by spiral elements 5', with the pitch of thread of the spiral element 5 in the length segment A being greater than that of the spiral elements 5'. The difference of densities of the series of rings 4 in Fig. 3 and of the difference of pitches of threads of the spiral elements 5, 5' in Fig. 4, respectively, results in that .each catheter in the length segment A provides a greater flexibility than in the region of the remaining two length sections. The following group of inventive solutions shown in Figs. 5 to 7 are designed by treat¬ ing the wall construction at the length segment A of a known catheter tube. In Fig. 5, the wall of the catheter tube is weakened at the length segment A by a series of annular grooves 6. In the embodiment shown, each groove 6 is essentially semicircular in section, the grooves 6 are equal to each other and arranged equi¬ distantly. However, as to the design and size of the section of grooves 6, analogous variations of embodiments as in case of rings 4 disclosed in connection with the em¬ bodiment of Fig. 1 are possible. Although not shown, it is evident that also a possibility of embodying is comprised by the invention, which, instead of grooves 6, foresees a groove spiral, preferably but not exclusively a single-stage one. Fig. 6 shows a situation that is practically contrary to the one of the preceding em¬ bodiment. The outer mantle surface of the catheter at the length segment A, where the diameter of the tube is reasonably reduced in comparison to that of the remain¬ ing length sections of the catheter, provides a series of annular ribs 7. In the embodi¬ ment shown, each rib 7 is essentially semicircular in section, the ribs 7 being equal to each other and arranged equidistantly. However, as to the design and size of the sec¬ tion of ribs 7, there are again possible analogous variations of embodiments as in case of rings 4 as disclosed in connection with the embodiment of Fig. 1. Although not shown, it is evident that also a possibility of embodying is comprised by the invention, which, instead of the series of ribs 7, foresees a rib spiral, preferably but not exclusively a single-stage one. Referring finally to Fig. 7, a further embodiment of a catheter is shown with the tube of the catheter providing increased flexibility at the length segment A, the length seg¬ ment A being designed as a straight circular-section bellows. In the embodiment shown, the tubular bellows consists of toroidal elements 8, with the elements 8 preferably being equal to each other and arranged so that the nominal diameter of the said elements coincides with that of the catheter tube. Although not shown, it is again evident that as to the design and size of the section of toroidal elements 8, there are also possible variations as in case of rings 4 of the embodiment of Fig. 1, and that within metes and bounds of the invention an embodi¬ ment is also comprised, which, instead of a series of toroidal elements 8, foresees a bulge spiral, provided that the respective manufacturing equipment is available. Each drawing comprises a schematically shown cuff S, i.e. a retaining element known per se, the cuff being fixed as to the location in the longitudinal direction on the length section of the catheter, which in the implanted state resides inside the patient's body. Practically, the cuff S indicates the respective section of the catheter to be implanted into the patient's body in contrast with the section of the catheter which will protrude from the body. It is thus obvious that the length segment A ac¬ cording to the invention is measured directly from the patient's skin. It is not to be considered impossible to advantageously reduce the spacing between the cuff S and the beginning point of the length segment A when using the catheter according to the invention. The said spacing should be as small as possible and in the prior art catheters it amounts - as stated in the aforementioned literature - to approx. 20 mm (in some cases the said spacing is greater, in others it is smaller). This is a fur¬ ther positive contribution of the disclosed invention to the progress of the respective technical field.

Claims: C LA I M S 1. A catheter, particularly a permanently implanted catheter, especially a peritoneal-dialysis one, particularly for such peritoneal dialysis where a catheter tube positioned normally to the surface area at the location of implantation, the catheter consisting of a flexible catheter tube and of at least one cuff which is stable in its posi¬ tion on the catheter tube, characterized in that the catheter tube provides a length segment (A) foreseen in the section of the catheter protruding from the patient, with the said length segment beginning next to the patient's skin, the general flexibility of the said length segment being greater than that of the remaining length section of the catheter protruding from the patient, so that the catheter tube protruding from the patient's abdominal wall easily bends at the said length segment, which results in that the moving of the free part of the catheter generates no substantial irritation of the entry/exit site of the sinus section of the subcutaneous tunnel. 2. Catheter of claim 1, characterized in that its length segment (A), whose general flexibility is greater than that of the remaining length section of the catheter tube protruding from the patient's body consists of a main tube (1) and two mantle tubes (2, 3) fitted individually onto the each end of the said main tube so that a spac¬ ing exists between them, whose length corresponds to the said length segment (A), with reinforcing rings (4) being arranged on the main tube (1) in the region of the said length segment (A), the reinforcing riiϊgs being held in a stationary manner on the main tube (1). 3. Catheter of claim 2, characterized in that the reinforcing rings (4) are advan¬ tageously round in section, equal to each other and positioned equidistantly. 4. Catheter of claim 1, characterized in that its length segment (A), whose general flexibility is greater than that of the remaining length section of the catheter tube protruding from the patient's body, consists of a main tube (1) and two mantle tubes (2, 3) fitted individually onto the each end of the said main tube so that a spac¬ ing exists between them, whose length corresponds to the said length segment (A), with a spiral element (5) being arranged on the main tube (1) in the region of the said length segment (A), the spiral element being held in a stationary manner on the main tube (1) or being integral with it. 5. Catheter of claim 4, characterized in that the material of the spiral element is typically round in section. 6. Catheter of claim 1, characterized in that its length segment (A), whose general flexibility is greater than that of the remaining length section of the catheter tube protruding from the patient's body, consists of a main tube (1) provided with stationary reinforcing rings (4) on its entire length, with the spacing of the reinforcing rings (4) in the region of the respective length segment (A) being greater than that of the reinforcing rings (4) at the remaining length sections of the main tube (1). 7. Catheter of claim 1, characterized in that its length segment (A), whose general flexibility is greater than that of the other length section of the catheter tube protruding from the patient's body, consists of a main tube (1) provided with station¬ ary reinforcing spiral elements (5, 5') on its entire length, with the thread (pitch of thread) of the reinforcing spiral element (5) in the region of the respective length segment (A) being greater than that of the spiral elements (5') at the remaining length sections of the main tube (1), the spiral elements being bound to the main tube or integral with it. 8. Catheter of claim 1, characterized in that the catheter tube provides annular grooves (6) at the respective length segment (A) located next to the patient's skin. 9. Catheter of claim 1, characterized in that the catheter tube provides annular ribs (7) at the respective length segment (A) located next to the patient's skin, the outer diameter of the respective mantle surface being advantageously smaller than that of the remaining length sections of the catheter tube. 10. Catheter of claim 1, characterized in that the respective length segment (A) located next to the patient's skin is composed of toroidal elements (8), which con¬ stitute a tubular bellows. 11. Use of a flexible tube as means for providing a length segment, whose flexibility in comparison to that of the remaining length section(s) of a tube assembly is intentionally accentuated. 12. Use of claim 11, characterized in that at a plastic tube for manufacturing a catheter, particularly one for permanent implantation, especially one for peritoneal dialysis, whose length segment having accentuated flexibility is made of a tube as¬ sembly composed of a flexible tube having high-degree smoothness of the inner mantle surface, and an outer reinforcement designed either as rings or as a spiral ele¬ ment.

Inventors: KENDA RAJKO, KENDA, RAJKO
Applicants: KENDA RAJKO, KENDA, RAJKO
Application year: 1995
Main classification: A61M25
IPC codes: A61M25