GB2156223A - Catheters - Google Patents

Abstract

A catheter (10, 20), particularly for urethral location and intermittent use, has a closed probe tip (13) of rounded shape which is assymetrically tapered relative to its longitudinal axis whereby the catheter can be variably directed by rotation during introduction. A side wall opening (21) is preferably located circumferentially round the catheter in corresponding manner with the tip off- set from the axis, this opening is preferably defined by a smooth surface continuous with the adjoining surfaces, the opening is preferably of generally cardioid shape with a concavely curved trailing end portion, and the opening is preferably bordered by smooth pimpling (22) in the catheter external surface. <IMAGE>

Description

SPECIFICATION Catheters This invention concerns catheters and more particularly urethral catheters intended for intermittent use.

Many authorities agree that intermittent catheterisation, hereinafter referred to as IC, is a safer way of managing urinary bladder dysfunction than is the use of an indwelling catheter, the former involving a lesser incidence of urinary tract infections and sequelae. However, infections still occur with IC and the question of whether there is a main cause of such infections remains debatable.

The present invention rests on the view that there is in fact a common cause of infections associated with IC and that this cause is trauma to the urinary tract lining during catheter introduction, this trauma enabling bacteria which are often present in the urine, even in people with good bladder function, to infect the urothelium.

Trauma can arise from lack of skill in catheter introduction and this will be particularly evident in relation to male patients for whom introduction is more difficult because of the longer, sinuous urethra. Poorly trained or inexperienced operatives can in fact easily fail to pass the catheter into the male bladder and, instead, produce a false passage by penetration of the urethral wall, this usually occurring in the membranous or prostatic portion.

Generally speaking, if, during IC introduction of currently-employed catheters, undue resistance is met, this can indicate a contracted sphincter, a kinked urethra, a difficult bend, an abnormal passive obstruction, or the opening of a false passage. A well trained or experienced operative will, in these circumstances, wait for at least a few seconds while keeping only a gentle pressure on the catheter to allow the sphincter to relax or the catheter material to soften from body heat and so bend slightly to negotiate a bend or obstruction. This technique is not readily learned and in its absence the tendency is to attempt to push through the resistance by applying increased pressure with trauma as a likely consequence. Moreover, this tendency is of significance because there is an increasing trend to self-catheterisation by patients.

An object of the invention is to alleviate this situation and it is accordingly proposed that IC introduction be facilitated by the provision of a catheter comprising a tube terminating at one end in a closed probe tip of rounded shape which is asymmetrically tapered relative to a rectilinear longitudinal axistherethrough.

The benefit of the proposed catheter is that it can be safely rotated within its own diameter, Thus, when undue resistance is met, reduced pressure is appropriate as before but it can be combined with slow rotation of the catheter whereby the tip searches for a route round the obstruction. The desired route will be associated with a reduction in introduction resistance recognisable by the operative. Also, this new technique is thought to be more readily learned because it involves continuing activity on the part of the operative rather than inactivity and so satisfies the normal wish to do something when confronted with a difficulty.

Improvement is also thought to be possible according to further features of the invention leading to a reduced likelihood of trauma during IC introductiori.

The catheters in current usage for IC are mainly of red rubber or PVC and each such material is a potential cause of trauma, even if only at the microscopic level, during each introduction. This trauma is most likely to occur in the very friable plasma membrane which lines the bladder and adjacent urethra, the trauma being caused by the edges of drainage eyes in the catheter and into which the urothelium easily prolapses, or by friction from the catheter walls. The former cause is more pertinent to PVC and the latter cause to red rubber.

It is preferred therefore that each drainage eye of the proposed catheter be defined by a smooth surface substantially continuous with the adjoining surfaces. In this connection the term "continuous" is intended to be construed in the geometrical sense as involving no discontinuity such as an angular formation or cusp which may, in the present practical context, act as a cutting edge.

Also, it is proposed that the outer surface of the catheter bordering each drainage eye can be smoothly formed with pimpling, or other convex second order modulation in shape, to reduce the tendency of the urothelium to prolapse thereinto.

In addition, it is preferred that the proposed catheter be made of silicone rubber of such composition as to be translucent at least in the tube.

This material can give a number of benefits. Visual monitoring for the presence of urine and for cleanliness is possible, as in fact is already the case with PVC but not red rubber. Friction can be reduced relative to both the prior materials, Silicone rubber is also readily amenable to accurate moulding which may facilitate the preferred eye formation.

Again, silicone rubber is repeatedly reusable following sterilisation by heat, without rapid deterioration as is the case with the prior materials.

Clarification of the invention may be gained by consideration of the accompanying drawings, given by way of example, in which Figure 1 illustrates in plan view an earlier conceived embodiment of a urinary IC catheter according to the invention; and Figure 2 illustrates the same embodiment in longitudinal sectional view taken at Il-Il in Figure 1, and Figures 3 and 4 respectively similarly illustrate the probe end portion of a subsequently conceived embodiment of the invention.

The catheter of Figures 1 and 2 is denoted generally at 10, it is about 400mm in overall length, and it is made of silicone rubber.

The major, intermediate portion of the catheter is tubing having a wall 11 and lumen 12 of uniform circular cross-sectional shape, the wall thickness and silicone rubber composition being such that at least this portion is translucent.

At one end this portion terminates in a solid body portion 13 serving as a probe tip for the purposes of catheter introduction during use. This portion is seen to be of a rounded shape asymmetrically tapered relative to a recilinear longitudinal axis therethrough, which shape can extend into the immediately adjacent tube. It is to be noted that this tapered shape involves no transverse extension beyond the diametrical limits of the adjacent circular tube when notionally projected longitudinally.

One or more openings are formed in the tube adjacent to the probe tip to serve as drainage eyes.

In the present instance there are two such openings 14 and 15, the first one being nearer to the tip and located in circumferential orientation relative to the tube in corresponding manner to the free end extremity of the tip, and the other one being further from the tip and diametrally opposed in circumferential location relative to the first opening.

Each opening is, as described above, defined by a smooth surface continuous with the adjoining surfaces of the tube wall and probe tip.

At its other end the tube portion terminates in a connector 16. The connector is enlarged diametrally both internally and externally relative to the tube wall, the inner surface enlargement being divergently tapered at 17 so that the connector serves as a socket of Luer type. The outer surface of the connector may be of any suitable shape but, in any event, is provided with a nipple 18 or other marker at a circumferential location in predetermined relationship with the asymmetrical taper of the tip. In the present instance the nipple is circumferentially located along the direction in which the asymmetrical taper of the tip is maximally off-set relative to the longitudinal axis of the catheter.

The catheter of Figures 3 and 4 is denoted generally at 20 and is essentially the same as that just described except for three differences.

Firstly, only one drainage eye opening 21 is considered necessary by virtue of the improvement due to the other features of difference.

Secondly, this opening 21 is seen to be longitudinally asymmetrical. More specifically the trailing end periphery is now concavely curved to provide a generally cardioid overall shaping in plan view. This shaping is found to be beneficial in the event of bending of the catheter in the region of the eye during insertion, the concave peripheral portion serving to inhibit outward distortion of the edges of the eye and consequent damage to the urothelium.

The remaining feature of difference is the provision of pimpling 22 over the outer surface of the catheter bordering the eye. The relevant pimples are of smoothly rounded shape, suitably substantially part-spherical, and smoothly blended with the adjoining surface areas. As noted earlier, this feature serves to obviate suction - induced urothelial prolapse into the eye during catheter introduction. This feature also serves to obviate such prolapse and consequent obstruction of the eye subsequently when the bladder contents are draining.

Although the invention has been described with more particular reference to the illustrated embodiments, it will be appreciated that variation is possible within the scope of the appendent claims.

Clearly some detail is variable, such as the precise shape of the probe tip taper, the number and location of the drainage openings, the form of the connector, and the form and location of the marker.

Also, while developed particularly for urinary IC catheters, the proposed probe taper and other features of the invention may find beneficial application to catheters for other purposes.

Claims (11)

1. A catheter comprising a tube terminating at one end in a closed probe tip of rounded shape which is asymmetrically tapered relative to a rectilinear longitudinal axis therethrough

2. A catheter according to Claim 1 having at least one opening in the wall of said tube adjacent said tip, said opening being defined by a smooth surface substantially continuous with the adjoining surfaces.

3. A catheter according to Claim 2 wherein one said opening is circumferentially located relative to said tube in corresponding manner to the free end extremity of said tip.

4. A catheter according to Claim 3 wherein said one opening is of generally cardioid overall shape in plan view, with a concave periphery at its trailing end portion relative to said probe tip.

5. A catheter according to Claim 3 or 4 comprising a further said opening located further from said tip than, and in diametrally opposed circumferential location to, the lastmentioned one opening.

6. A catheter according to any of Claims 2 to 5 having its outer surface bordering each said opening smoothly formed with pimples or other convex second order modulation in shape.

7. A catheter according to any preceding claim wherein said tube carries, at least adjacent its other end, a visual marker in a predetermined circumferential location therearound relative to such location of the free end extremity of said tip.

8. A catheter according to Claim 7 wherein said tube other end terminates in a relatively enlarged connector formation incorporating said marker.

9. A catheter according to Claim 8 wherein said connectorformation continues the lumen of said tube into a divergently tapered opening.

10. A catheter according to any preceding claim made of silicone rubber, the wall thickness of said tube and said rubber composition being such that said tube is translucent.

11. A urinary catheter substantially as herein described with reference to Figures 1 and 2 or Figures 3 and 4 of the drawings.