IE890620L - Dilatation balloon catheter - Google Patents

Abstract

The dilatation balloon catheter (10) has a catheter line (11) on which there is arranged in an axially immovable manner a flexible balloon (12) which can be expanded by pressure fluid. The balloon (12) has a braid tube (15) provided with at least one fluid-tight elastic covering (16, 17). The braid tube (15) is woven from two warps (21, 22) of elastomeric threads running in opposite directions. Woven into this braiding are strands (23, 23') of high-modulus fibres extending in the axial direction of the braid tube in such a way that the single strand (23; 23') runs over the threads of the one warp and under the threads of the other warp. The length of the expandable area of the balloon (12) amounts to at least 4 times the maximum outer diameter of this balloon area in the unexpanded state. <IMAGE>

Description

f The invention relates to a dilatation balloon catheter - hereinafter referred, to as "balloon catheter" by way of abbreviation - in accordance with the Preamble of Claim 1.

Next/ the following definitions are stated: " Fluid-tight" denotes impermeability towards gases, vapours«' and liquids. A fluid denotes a gas, vapour, or a liquid. A monofilament (often, also referred to as monofilament yarn, monofil yarn, monofil or continuous fibre) denotes a thread which consists of a single filament, irrespective of th® sis® of its diameter. A multifilament (also referred to as multifilament yarn, multifil yarn) denotes a thread which consists of a plurality of filaments. The filaments may preferably be continuous chemical fibres.

Balloon catheters/ to which the invention relates, 6an be so designed that the catheter tube is closed in fluid-tight manner at one of its ends. However, the invention also relates to balloon catheters wherein th© catheter tube has at least one lumen which extends over the full length of the catheter tube and which is open at both axial ends. In general, the invention relates to balloon catheters which are introduced from the outside into the bodies of living things, in particular of human beings, through natural or artificial openings. In the introduced state, the balloon can then be expanded by means of pressure fluid conveyed into it, which preferably may be gas or a liquid, in order to be held 3 firmly in the body opening concerned, in a ureter, or any other duct or channel, a vessel, an operation wound, or the like, and/or to form a closure means in this body opening or the like or to widen the body opening or the 5 like.

Balloon catheters in accordance with the invention may have different medical applications, for example for purposes of nephrostomy, for introduction into blood vessels, ureters, operation wounds, or any other medical 10 purposes.

In a known balloon catheter of this type (DE-OS 333/258), a shaft of the catheter has a tube made of plaited material which, over a relatively large region of its length,, is encapsulated in a non-resilient 15 covering made of semi-rigid material, which extends from the proximal end of the catheter over a considerable section of the length of the shaft. An outer covering mad© of resilient material extends over a smaller section of th© length of th© shaft, on or in th© region 20 of the distal end of the catheter, whereby this smaller section of the shaft is capable of being blown up and/or expanded in the manner of a balloon. This makes it impossible to expand the balloon beyond acceptable limits. 25 Dilatation balloon catheters are likewise known, in which the same two-lumen construction as described above is present in the catheter,, but here there is an outer covering which is made of non-resilient polyethylene (PE) produced by radiation cross-linking. Here, fluid is 30 forced into the balloon until the PE covering, which previously had been folded around the catheter in the unfilled condition, is unfolded to its maximum contour. During this unfolding, the internal pressure only increases negligibly, the pressure only rising markedly 4 when the maximum sis© of th© balloon is attained at the end of the unfolding process. The end contour is limited by the dimensions of the complete 'PE balloon sleeve. There are also dilatation balloon catheters in which the outer covering consists of resilient threads with a resilient coating.

Th© inflating process in this type of catheter takes place# from the beginning, with a rise of the pressure value; towards the end, when the max!mum contour is attained, the pressure value has ■also reached its maximum. Further increase of the pressure results in the balloon bursting. Here the contour limitation is produced by the elasticity values of the threads which are plaited into the wall of the balloon. However, on account of the braiding characteristic, these balloons become deformed into undesirable shapes,, for example into a banana shape, when the maximum inflation pressure is attained. The manipulation, e. g. the sliding of a tube (such as is necessary in nephrostomy balloon catheters) over the balloon is rendered very much more difficult, or is prevented altogether, by the "incorrect" shape.

An object of the invention is to produce a balloon catheter whose balloon should not be unlimitedly expandable, but which, furthermore,, can be acted upon internally with particularly high pressures (dilatation pressures) of the pressure fluid. This enables the balloon to push aside, by high dilatation pressures thereof, sinews, fascia, or other obstacles which may possibly offer a local resistance to the expansion of the balloon of the balloon catheter which is inserted into body openings, blood vessels, ureters, urethras, etc. It is also an object of the invention to give the balloon an elongate design and nevertheless to ensure that the balloon still possesses a tube-like shape even 5 in the expanded state, preferably in the substantially constant external diameter of its expanded region.

According to the invention, this object is achieved by a balloon catheter in accordance with Claim 1. 5 The balloon of the balloon catheter according to the invention cannot greatly expand, even under high pressures, despite the elastomer threads of both the groups of threads, because of the strands which are made of high modulus fibres. However, even when the balloon TO is of great length, the consequence is that th© external diameter of the expanded region of the balloon is substantially constant along its length, i. e. in the rectilinear position it has an approximately circular cylindrical shape. It is even possible for the expanded 15 balloon (except for its axial ends) to have a virtually perfect cylindrical shape, in particular a circular cylindrical shape, i. e. to have a constant circular cross section throughout. High modulus fibres are known, and therefore they require no further explanation. They 20 are characterised by low breaking strain of (at maximum) a few per cent, and high strength. The high modulus fibres can suitably consist, for example, of high-molecular polyethylene and/or para-aramid and/or carbon and/or other suitable high-strength materials. 25 High modulus fibres made of para-aramid are known e. g. under the trade name of "Kevlar". The elastomer threads of both the groups of threads which are plaited together are furthermore often also referred to as "braiding threads". They consist of elastomer fibres. These 30 braiding threads preferably may be monofilaments or multifilaments, or if desired, they can be manufactured from spinning fibres. These braiding threads may consist, for example, of synthetic plastics material, preferably segmented polyurethane, or of rubber, 35 caoutchouc, latex, or other suitable elastomer 8 materials. For example, their fibres may be those such as are commercially obtainable under the trade nam© "Lycra" (manufactured by Du Pont).

The threads of the strands are not designated as braiding threads, but - where appropriate - as strand threads, in order to differentiate them from the braiding threads. The strand threads also preferably may be monofilaments or multifilaments. However, it is also possible for the strand threads to be manufactured from spinning fibres, when in this case too, sufficient strength is present, together with low breaking strain.

The breaking strain of the threads of the strand threads preferably amounts to a maximum of 10%, particularly advantageously to a maximum of 6%. Breaking strains of at least 1% are particularly advantageous, preferably of minimum 2% and/or maximum 5%. The strands themselves then prevent too great an expansion of the balloon, if inadvertently the pressure fluid which serves for the expansion is introduced into the balloon with slightly excessive pressures. In this way, possible operational errors cause no adverse effects.

The strands also safely prevent an over-straining of the elastomer braiding threads, so that these latter retain their elasticity even after a long duration of operation, and so, even after a long duration of operation of the balloon catheter, the balloon resumes its original shape after each use. This balloon catheter therefore does not undergo any disadvantageous enlargement of the unexpanded balloon during operation.

Th© invention also results in the important advantage that th® balloon can be expanded with pressure fluid at high pressure, for example with pressures of several to many bar, e. g. of 2 to 20 bar, so that when the balloon expands it can, for example, push aside cartilage, fascia, sinews, muscle layers, and other obstacles, in consequence of the high internal pressure of the balloon. This results in an improved and rectilinear seating of the balloon catheter in the relevant vessel, opening, duct, or the like, of the relevant living thing, and also allows a particularly good sealing on the peripheral side of the balloon to be achieved.

The length of the balloon can to® different in accordance with the desired application, for example advantageously it may amount to 10 - 400 mm, approx. 40 - 300 mm being particularly advantageous.

Her®, the wall thickness of the balloon may be relatively small, for example 0. 5 - 1.2 mm or, according to the needs of the case, it may vary higher or lower. The catheter tube, that is to say the flexible catheter tube or a rigid catheter tube, likewise may have a small external diameter of, for example, 0. 8 - 3 mm, or more or less than that, according to what is required. The catheter tube preferably can have a profile that is approximately constant along its length, preferably having an annular external profile.

It is particularly advantageous, e.g. for easy introduction of the balloon catheter into body openings and the like, if the balloon in the empty, i. e. non-expanded, state, is arranged so as to be without folds, preferably lying closely against the catheter tube, and particularly advantageously against the entire circumference of the catheter tube which it surrounds.

The balloon must be sealed in fluid-tight manner on the outside. For this purpose, the braided flexible tube may have a fluid-tight expandable tubular-shaped 8 covering on its outside and/or inside. In many cases, such a covering may be arranged only on the inside or only on the outside of the braided flexible tube. Preferably, a covering can be provided not only on the inside but also on the outside of the braided flexible tube. The covering may consist, for example, of elastomer material, e. g. of synthetic plasties material, rubber or the like. If two coverings are provided, the two coverings preferably could be connected together non-detachably by means of adhesive or welded areas, penetrating through apertures in the braided flexible tube.

The inside covering and/or outside covering of the braided flexible tubs can preferably be stuck to the tube. The sticking can be performed adhesively by the introduction of additional adhesive, or also cohesively by soldering on the relevant covering or coverings.

The elastic strain of the covering or coverings can preferably be of such a value that it is not exceeded during operation.

The length of the expandable region of the balloon amounts to at least four times the external diameter of this region of the balloon in the unexpanded state, in order thus to achieve sufficient expandability of the balloon despite the low breaking strain of the strands. Preferably, this length of the expandable region of the balloon can amount to at least ten times and preferably at least fifteen times the maximum external diameter of this region of the balloon in the unexpanded state.

Advantageously, the braided flexible tube may be so constructed that, when the balloon is expanded by means of pressure fluid to such an extent that the strands are stressed to approximately 90% of their breaking strain, the internal diameter of the balloon amounts - in the expanded state - to a maxxjau.ni of five times, preferably a maximum of twice, and particularly advantageously a maximum of 1. 5 times, the internal diameter of th© non-expanded balloon.

The braided flexible tube may preferably be so constructed that adjacent strands are arranged such that the one strand passes over the threads of the first group of threads (viewed from the outside) and passes under the threads of the second group of threads, whereas the other strand passes under the threads of the first group of threads and passes over the threads of the second group of threads. However, advantageously other arrangements of the strands often also come into consideration. For example, the strands of the braided flexible tube may often be advantageously arranged such that alternate groups consisting of n adjacent strands pass over th© threads of the first group of threads (viewed from the outside) and pass under the threads of the second group of threads, and such that the groups of strands lying therebetween, each of which consists of m strands, pass under the threads of the first group of threads and pass over the threads of the second group of threads, n and m being whole numbers greater than 1 and n and in preferably being equal amounts for tooth groups of strands. Preferably, n and m may be equal to 2 or 3.

Furthermore, at least one strand, preferably all strands, may preferably consist of one single thread in each case. However, it is also possible, and likewise often advantageous, for at least one strand, preferably 10 all strands, to consist in each case of one bundle of threads which has several threads. Advantageously, the threads of the strands may be what are called "smooth" threads, i. e. they are non-textured. Likewise, the braiding threads of the two groups of threads may advantageous1y be smooth, i. ©. non-textured, threads.

Each thread of a group of threads may advantageously be so arranged that, viewed from the outside, it alternately passes over and under the threads of the other group of threads which it crosses.

The number of the strands of the braided flexible tube may advantageously correspond, at maximum, to the number of bobbins from which the braiding threads of the two groups of threads were unwound during the plaiting of the braided flexible tube. In a preferred manner, the number of strands may correspond to half this number of bobbins, but also it may be greater or smaller.

The securing of the balloon on the catheter tube may be achieved in any suitable manner whatsoever, preferably in accordance with the measures according to Claim 14 or IS.

Embodiments of th© invention are illustrated in the drawings, which show: Fig. 1 a partly sectional and broken side view of a balloon catheter in accordance with an embodiment of the invention, Fig. 2 an enlarged broken longitudinal section through the balloon catheter in accordance with Fig. 1, Fig. 3 a section through the balloon catheter in accordance with Fig. 2e viewed along the sectional line 3-3, Pig. 4 an illustration of a braided flexible tube for the purpose of explaining its structure, viewed in th® direction of its longitudinal axis, wherein the other parts of the balloon catheter are indicated in dash-dot lines in this embodiment, Fig. 5 a cut-out top view of a winding of the braided flexible tube in accordance with Fig. 4, for the purpose of illustrating its structure, Fig. 6 a variant of the braided flexible tube in accordance with Fig. 4, likewise viewed in the axial direction thereof.

The balloon catheter 10 in accordance with Figures 1 and 2 has a catheter tube 11 and an expandable balloon 12 which is arranged on the left-side end region thereof and has no folds whatsoever. Th© catheter tube 11 is constructed as a thin flexible tube which is closed on the left-sid® front end and whose cross-sectional profile is uniformly circular, and which in this case is made of synthetic plastics material, for example polyurethane; however it may also be made of other suitable flexible or rigid materials which do not disadvantageous1y become expanded due to the pressure fluid (e. g. air or liquid) which serves in each case for expanding the balloon 12 and which is introduced into th© lumen 13 of this flexible tube, i. e. in this embodiment, into its one single continuous duct. Because of the construction of the balloon 12 described 12 hereinafter, this pressure fluid can have a very high dilatation pressure - i. e. pressure for expanding the balloon - of e. g. 6 to 20 bar. The balloon 12 also has the property that, even at relatively low pressures 5 (dilatation pressures) of the pressure fluid, it expands almost to its full size, and then, when the pressure is further increased, further expansion is minimum. But then by means of higher pressures the balloon is capable of pushing aside muscles,, sinews., and other tissue parts 10 or the like which may possibly constitute obstacles and which offer a local resistance to its expansion, so that by using high pressures it is possible to perform this pushing aside, or to refrain from doing so by using lower pressures. 15 When the catheter tube is closed at one of its ends - as illustrated - it is sufficient for it to have only one single lumen 13, as is the case in this embodiment, and then the pressure fluid for expanding the balloon 12 is introduced into th© lumen, for which purpose holes 14 20 are provided in the wall of the lumen 13, opposite the expandable region of the balloon 12.

In its non-expanded state, th© balloon 12 also lies with its expandable region close against the catheter tube, and in fact, particularly advantageously against 25 the entire circumference of the catheter tube which it surrounds.

Th© balloon 12 has a braided flexible tube 15 which is covered both on the outside and the inside by a fluid-tight resiliently expandable covering 16, 17, 30 preferably elastomer coverings 16, 17, which are glued or welded together by means of bridges which penetrate through apertures in the braided flexible tube 15. The expanded state of the balloon 12, brought about by pressure fluid introduced into the balloon 12 through ia its lumen 13 and the holes 14, is illustrated in dash-dot lines, and it can be seen that the expanded region of the balloon 12 has a substantially circular cylindrical shape. By drawing off the pressure fluid, 5 the balloon 12 returns completely to its original shape (illustrated in unbroken lines) even after it has been in operation for a long time. It now once more lies against the catheter tube 11 along its full length and without any folds. The balloon 12 does not have any 10 folds in the expanded state either.

A possible and advantageous construction of the braided flexible tubs 15 is now explained in further detail, with reference to an embodiment illustrated in Figs. 4 and 5, wherein, in Fig. 4, the catheter tube 11, .j^ in contrast to Figs. 1 to 3, has two lumens 13', 13".

The lumen 13' represents the main lumen which does not communicate with the balloon 12 so that it can be open at both ends of the catheter tube 11, whereas the lumen 13" is open only at one end of the catheter tube 11. 2Q This lumen 13" communicates in a fluid-conducting manner with the interior space of the balloon 12 via at least one hole 14.

The braided flexible tube 15 illustrated in sectional diagrammatical view in Figs. 4 and 5 is 25 plaited from two contra-directional groups of threads 21, 22, each with eight braiding threads 21 and/or 27' . In each case eight bobbins are used, whilst interweaving eight strands 23, 23' which extend in the axial direction of the braided flexible tube 15 and which 3Q consist of high modulus fibres, a. g. advantageous 1 y of polyethylene or carbon. The elastomer braiding threads of the group of threads 21 are therefore designated by 27, and those of the group of threads 22, by 27' , only a few of these braiding threads 27, 27' being shown in oc sectional view. 14 In this embodiment,, each strand 23 and/or 23' consists of a monofilament or multifilament, preferably of a smooth monofilament and/or multifilament consisting of smooth filaments. In this embodiment, this braided 5 flexible tube has a total of eight strands 23, 23' . In this case it is particularly advantageous if, during plaiting, the braiding threads 27, 27' come from eight bobbins, i. e. if one single braiding thread 27 and/or 27' runs off from each bobbin, each group of threads 21, 10 22 consists of eight braiding threads, although for example the number of the strands 23, 23' may also be higher or lower, but preferably corresponds at maximum to the number of bobbins from which the braiding threads 27, 27' run off during the plaiting of the braided 15 flexible tube. If desired, however, it may also be higher or lower, e. g. it may correspond to a quarter of the number of bobbins. Advantageously the number of bobbins is higher the greater the maximum external diameter of the inflated balloon and the greater its 20 dilatation pressure.

In this particularly advantageous embodiment, the strands 23, 23' pass between the braiding threads 27, 27', in the manner illustrated, in such a way that each alternate strand 23 - viewed in the peripheral direction 25 of the braided flexible tube - passes under the braiding threads 27 of the group of threads 21, and passes over those of the group of threads 22. The strands 23' which lie therebetween pass under the braiding threads 2T of the group of threads 22,, and pass over the braiding 30 threads 27 of th® group of threads 21. In accordance with Fig. 5, the strands 23, 23' are distributed at regular centre-angles around the periphery of the braided flexible tube 15, relative to the longitudinal axis thereof running parallel to the strands; however, 35 ®. g. in accordance with Fig. 8, they may also be < ■? arranged at irregular centre-angle distances from one another.

Each strand 23, 23' thus extends in the axial direction of the braided flexible tube. The strands 23, 23' are parallel to one another and do not extend helically or spirally around the flexible tube, but when the balloon is straight, each strand extends in a central longitudinal plane of the braided flexible tube 15.

A numerical embodiment of th© braided flexible tuba 15 will now be introduced: Wall thickness of the balloon 12, approx. 0. 9 mm. External diameter of the catheter tube 11, approx. 2. 3 mm, Maximum external diameter D of the expandable region of the non-expanded balloon, approx. 4. 1 mm. Overall length hg of the balloon 12, approx. 200 mm. Length La of the expandable region of the balloon 12, approx. 170 mm. The braiding threads 27, 27' are multifilament threads which consist of filaments made of rubber, e. g. of Lycra (Lederer). Th© fineness of the individual braiding thread 27, 27' amounts to approx. 40S dtex. Its tension elasticity modulus amounts to 0.046 N/mm^. Each strand 23 and 23' is a multifilament made of para-aramid, having a fineness of 380 den. Like the braiding threads 27, 27' , the strand® 23, 23' are stuck to the coverings 16e 17 and are glued or welded together by means of bridges which penetrate through the apertures in the braided flexible tube 15.

The balloon 12 forms a circular cylindrical flexible tube in the rectilinear state, before being pushed onto the catheter tube 11 and being secured thereon in axially immovable manner. 18 In the embodiment according to Figs. 1 and 2, the braided flexible tube is secured on the catheter tube 11 by means of a thread (winding thread) 24 wound tautly around it at short axial longitudinal end regions. This winding thread extends slightly beyond the two longitudinal ends of the braided flexible tube 15 and of th© inner covering 17, onto the catheter tube 11. Only afterwards is the outer covering 16 applied. It may be applied, e. g. by immersing th© region of the balloon catheter 10 which has the balloon 12 into a bath of a polymer solution, so that the resulting outer covering 16 is an outer coating or tuba of the balloon 12 and possibly also extends beyond th® braided flexible tube 15 and the tubular-shaped inner covering, which also completely envelops the winding threads 24 so that they cannot become free. In this mode of construction, the outer covering 16 is automatically stuck or welded to the inner covering 17 and is also stuck to the braided flexible tube 15, when the threads thereof 27, 27' , 23, 23' consist of material which is capable of being stuck to the material of the outer tube. This is particularly advantageous. After the catheter tube with the balloon has been removed from the aforesaid polymer solution, the outer covering 16 then dries. The regions of the catheter tube 11 which are not intended to be provided with an outer covering are, in so far as is possible, not immersed into the polymer solution.; otherwise, the outer covering in the relevant region or regions of the catheter tube 11 can further be coated with a protective layer, @. g. with wax, before immersion into the bath, this protective layer allowing easy removal of the outer covering in these regions.

The balloon catheter can serve various different purposes, for exaa\pl© as a dilator for a branch canal, as a nephrostomy dilator, a ureter dilator, a urethra dilator, a vascular stenosis dilator, and also for other 11 areas of use.

If the balloon 12 of the balloon catheter 10 is expanded by the introduction of pressure fluid, then amongst other properties it also displays the following outstanding on©. The expandable region of the balloon retains a practically circular cylindrical shape during expansion, and at a particular, still relatively low, pressure of the pressure fluid, the maximum external diameter of the balloon is virtually attained. When the pressure of the pressure fluid is further increased, this maximum external diameter is virtually unaltered. The pressure can then be increased until it is near to bursting pressure, at which the braided flexible tube would burst, breaking at least one strand. If for example the bursting pressure amounts to 24 bar, then the pressure of the pressure fluid can be provided e. g. at a maximum of approximately 12 bar in order to have a fully sufficient safety limit before the bursting pressure is reached.

The balloon catheter is also characterised by the fact that, after each expansion, when the pressure of the pressure fluid is decreased again,, the balloon 12 returns back into its original shape,, in which it again lies closely against the peripheral wall of the catheter tube. This therefore produces constant properties for inserting the balloon catheter into branch canals, body openings, operation wounds, or the like, even after often-repeated use. .18