CATHETER HAVING AN INTERNAL EXCHANGEABLE MEMBER

Abstract: Catheter to be inserted by surgery into the body, which is provided with an internal member (17), the catheter (15) as well as said member consisting of a low friction material, a gap being provided between the member and the catheter in order to allow replacement of the member in the catheter by the member being pushed thereinto and being withdrawn therefrom, respectively.

Description: TITEL: CATHETER HAVING AN INTERNAL EXCHANGEABLE MEMBER The invention relates to a catheter which is in¬ tended to be inserted by surgery into the body and may be connected to a cutaneous passageway, for example of the type described in WO 87/06122. The catheter according to the invention is provided with an internal member pushed thereinto, for example a lining, as disclosed in US-A-3621848. The invention relates especially to the type of catheters which are used to establish a permanent connection to the . abdominal cavity, vasculars, or other local in the body, in order to supply continu¬ ously through the catheter pharmaceuticals for treatment of cronical diseases, or to dispose body fluids or other substances from the body. The catheters used today in this connection are produced from biocompatible polymers, for example natural rubber, silicone, or polyurethane, since the catheter must be soft and flexible within the body. The problem with these catheter materials is, how¬ ever, that pharmaceuticals which are to be supplied to the body through the catheter often react with the catheter material. Thus, for example insulin can be crystallized or polymerized in the catheter with following obstruction thereof. A catheter which is used for disposal of fluid from the body also runs the risk of being obstructed by more or less solid particles which occur in the fluid, or by the pro¬ duction of blood clots. The purpose of the invention is to eliminate these problems, and this is achieved by the catheter according to the invention having obtained the char¬ acterizing features of claim 1. From the above mentioned US-A-3 621 848 a ca¬ theter is previously known which is provided inter¬ nally with one or more thin removable but not ex¬ changeable linings which are successively removed when solid particles are gathered in the catheter or blood clots are formed which more or less obstruct the passage through the catheter. When such an ob¬ struction occurs the lining which limits the lumen in the catheter is withdrawn, whereupon present solid particles or blood clots will follow the lin¬ ing out from the catheter. As far as several linings are arranged this procedure can be repeated a number of times but when the last lining has been withdrawn the catheter has to be exchanged, which can be done by a surgical operation only. Thus, a catheter is referred to which has a relatively limited time of utilization contrary to the catheter according to the invention which is intended to be used for a long time, maybe during the greater part of a life¬ time, without having to be exchanged and which can be "renewed" without any surgical operation. For further explanation of the invention refer¬ ence is made to the enclosed drawings in which FIG 1 is a cut perspective view of a cutaneous passageway with a catheter according to the in¬ vention connected thereto, FIG 2 is an enlarged exploded axial sectional view of the catheter according to the invention and means for the attachment thereof, FIG 3 is an enlarged axial sectional view which illustrates the attachment of the exchangeable lining in the catheter, and FIG 4 is an enlarged axial sectional view which illustrates withdrawal of the lining from the catheter. With reference to FIG 1 is shown a cutaneous passageway of the type described in WO 87/06122. For further details of the construction of the cutaneous passageway reference is made to this publication. It is sufficient to note that the cutaneous passageway comprises an internally threaded housing 10 with an externally threaded plug 11 screwed thereinto, which encloses a sealing body 12 of elastical sealing material. Inside the housing there is provided a bottom plate 13 of titanium forming a nipple 14 at the lower side thereof. A catheter 15 which prefer¬ ably consists of PTFE but can also consist of poly¬ ethylene or FEP is inserted into the nipple 14 and enclosed by an outer envelope 16 which preferably consists of polyurethane but can also consist of silicone or any other suitable biocompatible ma¬ terial. The envelope suitably is extruded onto the outside of the catheter, whereby the envelope and the catheter will engage each other without air and gas bubbles occuring therebetween, and the envelope is shrinked onto the catheter so that the catheter and the envelope are kept together by friction which does not prevent them from being separated in order to thread the envelope onto the nipple 14, while the catheter passes into said nipple as shown in the drawings. If the catheter did not have an envelope 16 there would be an obvious risk that the lumen of the catheter could be obstructed when the catheter is bent - such a bending cannot be avoided in most cases when the catheter is located in the body - whereby a flow through the catheter would be stopped. The envelope prevents such an obstruction if the catheter is bent. Inside the catheter a lining 17 is provided which like the catheter preferably consists of PTFE but also can consist of polyethylene or FEP, and this lining forms a conically funnel-shaped end por¬ tion 18. The lining is passed through a central conical aperture 19 in a plate 20 made of polyester which rests on top of the bottom plate 13 and is guided therein by means of two pins 21 on the lower side thereof, which are passed into holes 22 in the bottom plate. The material of the catheter and the lining is a low friction material, and if the material is PTFE, this is a typical low friction material which makes it easy for the lining to slide through the ca¬ theter. In a practical embodiment the most favour¬ able conditions in this respect are achieved if there is a circumferential gap between the catheter and the lining of a size in the range of 0.02-0.05 mm. This size of the gap has shown to be optimal. If the gap is larger, there is a risk that contaminants can get in between the catheter and the lining and that surrounding body tissues may grow into the gap, and if it is smaller there is a risk that the lining cannot be passed through the catheter. As an example of the dimensioning of the ca¬ theter, lining, and envelope, the following measures are given: Catheter internal diameter 0.55 mm external diameter 0.8 mm Lining internal diameter 0.3 mm external diameter 0.48 mm Envelope internal diameter 0.8 mm external diameter 1.3-1.4 mm To insert the lining 17 into the catheter 15 a guide 23 is suitably used which consists of a stain¬ less steel wire with a diameter of 0.20-0.25 mm. Said wire forms a loop 24 at one end thereof, and just below the loop there is threaded onto the guide a short plastic tube 25. With the lining 17 passed through the plate 20 so that the conical end portion 18 is resting in the conical aperture 19 arranged as a seat, and with the guide 23 inserted into the lin¬ ing, the lining is passed through the central aper¬ ture of the bottom plate in connection with the nipple 14 into the catheter 15 until the plate 20 is resting on the bottom plate 13 with the pins 21 in¬ serted into the holes 22, FIG 3. Then, the guide 23 is withdrawn from the lining at the loop 24, and in order to prevent the lining from following the guide, which could happen if the catheter follows a winding path, such that the friction between the lining and the guide becomes sufficiently great at the bends of the leader to drag the lining along, it is possible to hold the tube 25 against the end of the lining at the fingers during the withdrawal of the guide and in this way to prevent the lining from being dragged along. The lining is as easily withdrawn by means of a sleeve 26, FIG 4, preferably made of plastic, which is pressed down over the plate 20 to engage a shoul¬ der 27 with the plate at the outer edge thereof. The sleeve has a bevelled edge 28 and a pair of dia¬ metrically opposite slots 29 allowing said sleeve to be easily pressed down over the plate 20 while the sleeve is expanding elastically. The sleeve is then pulled back, carrying along the plate 20 and thus the catheter, which is positively engaged with the plate at the end portion 18 thereof, the lining 17 being withdrawn from the catheter 15. At the inner end of the catheter, the end that is to be embedded into the body, the lining may pro¬ ject from the catheter or suitably end at the level of the catheter. If it ends inwardly of the end of the catheter there is a risk for crystallization or other obstruction to occur inwardly of the end of the catheter in the part of its lumen, which is not covered by the lining. The lining 17 may be perforated at least in a portion adjacent the inner end thereof, which in that case is closed, allowing the lining to receive a diagnostic or therapeutic substance. Within the catheter there may be provided in¬ stead of the lining a solid, flexible rod, which at its inner end is provided with or formes a member for sampling. Such a member may consist of for example an attached silicone plate. The invention has been described in connection with a cutaneous passageway the catheter through a lining 17 being connected to an outer catheter 30, but obviously the invention can come in practice also with catheters which are not connected to a cutaneous passageway but is passed directly out from the body.

Claims: CLAIMS 1. Catheter to be inserted by surgery into the body, which is provided with an internal member in¬ serted thereinto, c h a r a c t e r i z e d in that the catheter (15) as well as said member (17) consist of a low friction material with a gap be¬ tween the catheter and the member in order to allow replacement of said member in the catheter by the member being pushed thereinto and being withdrawn therefrom, respectively. 2. Catheter according to claim 1, c a r ¬ a c t e r i z e d in that the member and the ca¬ theter consist of fluorine or olefine plastic. 3. Catheter according to claim 2, c h a r ¬ a c t e r i z e d in that the member and the ca¬ theter consist of PTFE. 4. Catheter according to any of claims 1-3, c h a r a c t e r i z e d in that between the mem¬ ber and the catheter there is provided a circum¬ ferential gap of a size of the order of 0.02-0.05 mm. 5. Catheter according to claim 1, c h a r ¬ a c t e r i z e d in that the member (17) consists of a tubular lining. 6. Catheter according to claim 5, c h a r ¬ a c t e r i z e d in that in the lining there is provided a guide (23) consisting of a metal wire, which can be withdrawn from the lining. 7. Catheter according to claim 5, c h a r ¬ a c t e r i z e d in that the lining is perforated at least in a portion thereof adjacent its inner end and is arranged to receive a diagnostic or thera¬ peutic substance. 8. Catheter according to claim 7, c h a r ¬ a c t e r i z e d in that the inner end of the lin¬ ing is closed. 9. Catheter according to claim 1, c h a r ¬ a c t e r i z e d in that the member consists of a solid, flexible rod. 10. Gatheter according to claim 9, c h a r ¬ a c t e r i z e d in that the rod at the inner end thereof has a member intended for sampling, for example a silicone plate. 11. Catheter according to claim 1, c h a r ¬ a c t e r i z e d in that the catheter externally is surrounded by an envelope (16) . 12. Catheter according to claim 11, c h a r ¬ a c t e r i z e d in that envelope (16) consists of polyurethane or silicone. 13. Catheter according to claim 12, c h a r ¬ a c t e r i z e d in that the envelope (16) is ex¬ truded onto the catheter (15) .

Inventors: AXELSSON ROBERT, SVENSSON JAN, AXELSSON, ROBERT, SVENSSON, JAN
Applicants: AXELSSON ROBERT, SVENSSON JAN, AXELSSON, ROBERT, SVENSSON, JAN
Application year: 1990
Main classification: A61M25
IPC codes: A61M25