GB2318513A

GB2318513A - Device for measuring urethral compliance

Info

Publication number: GB2318513A
Application number: GB9722038A
Authority: GB
Inventors: Robert Lee Cannon; Philippe Lourdel
Original assignee: VERMED
Current assignee: VERMED
Priority date: 1996-10-18
Filing date: 1997-10-17
Publication date: 1998-04-29
Anticipated expiration: 2017-10-17
Also published as: FR2754701A1; CA2218787A1; DE19746023A1; GB9722038D0; GB2318513B; FR2754701B1

Abstract

The device comprises a probe (1) with a tube (2) of diameter (D) pierced by at least one longitudinal duct (4, 5, 6) and provided with at least one pressure pick-up means each communicating with its respective duct, a means of fluid supply of the said duct and a means of measuring the pressure of the said fluid. The pressure pick-up means comprises an annular element (Z1, Z2, Z3, 15), the largest diameter (D1) of which, in the active position of pressure measurement, is greater than the diameter of the said tube. The probe may comprise at least two rigid olive-shaped elements of different diameters and each pierced by an orifice communicating with an internal duct supplied with fluid, the pressure of which can be measured. According to a further embodiment the probe comprises a balloon supplied with fluid and whose pressure is verified.

Description

1423 2318513 DEVICE FOR MEASURING URETHRAL COMPLIANCE The invention

relates to a device for measuring urethral compliance.

It is known that the lower excretory passage principally consists of the bladder connected to the urethra by the striated sphincter. One of the troubles which causes inconvenience in everyday life is incontinence which is an involuntary loss of urine caused by dysfunction of the bladder and/or sphincter. urine loss takes place when the forces of expulsion are greater than the restraining forces exerted by the urethra. The restraining forces are urethral pressure and strength.

Urethral pressure is maintained by the tonic activity of the smooth and striated muscle fibres which form the sphincteral mechanism of the bladder. It diminishes steadily with age, particularly after the menopause in women.

One method of diagnosis involves carrying out urodynamic examinations which permit in particular the determination of the filling pressure of the bladder, the urethral strength, i.e. the forces which oppose the passage of the urine in the urethra, and the maximum urethral pressure. The latter expresses the quality of the smooth and striated sphincters, on which continence or incontinence largely depends.

Urethral compliance is an important characteristic of the urethra which ought to be able to recover its compression properties when it is subjected to mechanical stresses. As the urethra is not a closed cavity like the bladder, its compliance cannot be measured by simple filling.

A known method consists of introducing probes of increasing diameter provided with a lateral orifice into 1423 2 the urethra. A liquid is perfused into a probe and its pressure, which corresponds to the pressure exerted on the orifice by the muscle of the urethra, is measured. The probe is moved along the urethra and a urethral pressure 5 profile is obtained for each probe diameter.

Another known method of measuring urethral compliance is to use probes of decreasing sizes. A probe having a diameter D, on one segment of given axial length, and a diameter D. smaller than D1 on another segment of the same axial length may be used for example. The wall of the probe is pierced at the first segment and at the second segment. When the urethra is supple, the pressure P, of the perfused liquid which comes out at the first segment of large diameter D1 is substantially equal to the pressure P, of the perfused liquid which comes out at the second segment of smaller diameter D2.

When the urethra walls lose elasticity, the urethra exerts a stronger pressure P, on the segment of large diameter D, than the pressure P2 on the segment of smaller diameter D2. Generally speaking, it is considered that an increase in the maximum urethral pressure beyond a certain threshold dependent on the size of the probes is indicative of urethral fibrosis. In the case of incontinence, a fibrosis of the urethra leads to the fitting of an artificial sphincter. If there is no fibrosis of the urethra, the problem is one of sphincteral insufficiency which can be repaired by surgery.

A known device of this kind enables changes in the elasticity of the urethra to be diagnosed by continuously taking pressures on each of the orifices at the same time whilst moving the probe. Compared to the system which has several distinct probes, it enables compliance to be recorded directly on one graph as a function of the position of the probe in the urethra.

1423 3 This known device does not, however, permit the pressure-taking to be centred on a reduced surface at the level of the sphincter between the bladder and the urethra, because the pressure measured is influenced by all the pressures exerted along the cylinder to which the pressuretaking relates.

The known probe is difficult to position at specific places in the urethra, the pressure measurements being less accurate.

The object of the invention is to solve these problems.

An object of the invention is to take more accurate pressure measurements so as to obtain a better picture of the compliance of the urethra over its entire length at each of its points, which enables imperious incontinence due to an anarchic variation in the pressure of the urethra to be diagnosed.

For this purpose the invention relates to a device for measuring urethral compliance, comprising:

- a probe with a tube of diameter (D) pierced by at least one longitudinal duct and provided with at least one pressure pick-up means each communicating with a duct, - a means of fluid supply per duct and, - a means of measuring the pressure of the said fluid, characterized in that the said pressure pick-up means comprises an annular element mounted on the tube, of convex profile in the active position of pressure measurement and the largest diameter of which is greater than the diameter of the said tube.

1423 4 In this way the zone of urethral pressure measurement is localized, selectively so to speak, on an axially reduced dilation zone - the element is preferably oliveshaped, i.e. of ovoidal or substantially spherical profile - and not a straight and very long cylinder as in the devices of the prior art.

According to a first embodiment each element is rigid or relatively inflexible, of annular form coaxial to the tube, and provided with at least one pressure-taking orifice at its largest diameter.

Preferably the probe according to the invention comprises at least two elements constituting dilation zones of different diameters and spaced apart. In particular the diameters are decreasing from the distal end of the tube onwards.

Preferably, when there are at least three zones, they are equidistant, by approx. 70 mm for example. The average size D of the tube is CH13 (path 13) for example, size D3 is CH16, size D2 is CH22 and size D, is CH29.

According to a preferred embodiment of the invention each element has a pressure measurement zone in the form of a groove which is circumferential and perpendicular to the longitudinal axis of the probe.

An orifice opens into the circumferential groove and permits a communication between the duct of the urethra and the corresponding duct inside the probe. When the urethra is sufficiently elastic it contracts around the measurement zone and limits the flow of the perfused liquid. The liquid pressure is measured inside each duct at the proximal end of the probe, the distal end of which is closed. Pressures P, , P2. and P3 corresponding to different diameters are equal when the urethra has good elasticity because it contracts to a greater degree at the groove of 1423 5 the zone of smallest diameter than at the zone of larger diameter.

When the urethra loses its elasticity, pressures P1, P2 and P, are dif f erent and increase when the diameter of the 5 zones increases.

Because of the localization of the dilation zones in narrow annular bands, when the probe is moved slowly the pressures are accurately measured at different points of the urethra, it being possible for these points to be very close to each other. This is an important advantage compared with the prior art in which the measured pressures are difficult to localize along the urethra because of the width of the measurement band.

According to a second embodiment the pressure pick-up means is constituted by an inelastic balloon in the area of measurement, mounted on the tube. This balloon communicates with a duct inside the tube, supplied with fluid. It is initially filled with fluid at atmospheric pressure. The volume of fluid does not exceed its dead volume, its walls are not dilated. As in the preceding solution, the pressure of the fluid which is capable of being measured is a function of the pressure exerted locally on the pressure pick-up means by the urethral wall.

The invention will be better understood, and further objects, advantages and features thereof will emerge more clearly from a reading of the description which follows of preferred embodiments which are provided by way of nonexhaustive example and which are accompanied by two pages of drawings in which:

- Fig. 1 is a diagrammatic sectional view of a first embodiment of a urethral compliance measuring probe according to the invention; 1423 6 Fig. 2 is an enlarged view of a dilation element, the variation in diameter of which is localized; - Fig. 3 is a curve showing the variation of the urethral pressures as a function of the diameters of the 5 dilation zones; - Fig. 4 is a sectional view of a urethral compliance measuring probe according to the prior art; - Fig. 5 is a sectional view of a second embodiment of a probe of the device according to the invention.

With reference to the drawings, Fig. 1 shows a probe 1 which forms part of a device for measuring urethral compliance. This probe 1 comprises a tube 2 with several longitudinal internal ducts or slots 4, 5, 6 which are capable of being introduced into the urethra. The tube 2 is closed at its distal end 3, i.e. the end away from the operator. In contrast, its proximal end is provided with fluid supply tubes 41, 51 and 61, each connecting to a duct 4, 5, 6 respectively. Although this is not shown, the tube 2 may comprise an additional duct opening at the distal end of the probe and enabling a communication with the bladder, its filling for example, to be ensured, when the probe is in place in the urethra.

According to the first embodiment shown, the tube 2 comprises three pressure pick-ups also forming dilation zones Z.. Z, and Z3.

The tube has a diameter D and each of the pick-ups comprises an annular element with a profile which is convex overall, olive-shaped for example, moulded with the tube 2 or added on. The maximum external diameter of the transverse sections, D1, D2 and D3 is greater than the diameter D of the tube 2. In the embodiment shown, the element Z, the closest to the distal end 3 of the tube, has a diameter D1 larger than the diameter D2 of the 1423 7 element Z2 located upstream and itself larger than diameter D3 of the element Z3 but another embodiment with other arrangements is possible.

A larger number of elements Z,, Z2# Z3f..... Z. mav be provided, their maximum diameter decreasing from the end 3 in the upstream direction or vice-versa according to the mode of operation chosen for taking the measurements. The elements Z1. Z29 Z. Z, are each pierced by an orifice, 01, 0,, 0, respectively. These orifices permit communication of the exterior of the probe 1 with the corresponding duct inside it 4, 5, 6 respectively and by this duct with a means of pressure measurement and of fluid supply.

According to the invention the pressure pick-up elements are also dilation means by virtue of their geometry. When one moves along the probe, the diameter increases gradually from diameter D up to a maximum diameter DJ. D2f D3..... D,, gradually to return to diameter D on a short axial length L.

According to the invention, the elements Z1, Z2f Z3 Z, preferably have a smoothed-off profile in the form of an arc of a circle or a curve approximating to it.

Preferably the annular surface is as narrow as possible at its maximum diameter; this is the pressure-taking surface.

The elements Z1. Z21 Z3..... Z, are spaced apart, preferably equidistant, and are not therefore adjacent to each other, unlike the device of the prior art.

Preferably the zones ZI, ZI 1 Z3 are equidistant. by the order of 70 mm for example. The size D of the tube is, for example, CH13 (4.33 mm), D, is CH16 (5.33 mm), the diameter D2 is CH22 (7.33 mm) and D1 is equal to CH29 (9.67 mm).

As can be seen in Fig. 1, the elements forming the urethral pressure pick-up each comprise an orifice 01, 02, 1423 8 .. opening into a peripheral groove RI, R2, perpendicular to the axis; these grooves thus constitute the annular pressure-taking surfaces.

Thus, when the probe shown in Fig. 1 is introduced into the urethra the walls of the urethra successively come into tangential contact with the pick-up Z, then intermediate Z, and then with Z,. The pressure measurement at each point is carried out for three dilations. Thanks to the rounded profile of the pick-up, it will be understood that the annular band R1, R2, R3 respectively, on which the pressure is measured, is narrower than when the pick-up is of tubular shape.

The pressure measurements may also be taken by withdrawing the probe. In this case the arrangement of the pick-ups is reversed.

If the urethra is elastic the maximum urethral pressure measured at R,, R2 7 R3 varies little as a function of the dilation of the tissues of the urethral wall. When one passes from one diameter to a smaller dilation diameter, the tissues will retract without difficulty. On the other hand, if the urethra is rigid, a considerable pressure rise will be observed in the sense of the dilation; pressure P, exerted on the zone Z., of largest diameter is greater than that of P, exerted on the zone Z2 of intermediate diameter and this is itself greater than that of P3, exerted on the zone Z3.

Fig. 3 shows the variations in the maximum urethral pressure as a function of diameters D,, D2 and D, of the elements Z,., Z, and Z,, in the case of an elastic urethra (1) and a urethra with fibrosis (2). The device of the invention permits a more accurate plot of these curves and makes the diagnosis more reliable.

The same device also enables a profile of the elasticity of the urethra to be plotted along its entire 1423 9 length. For this purpose the probe is moved from one end of the urethra to the other and the pressure measured continuously at each point.

When using a urethral compliance measuring probe according to the prior art and comprising maximum pressure measurement zones which are tubular and adjacent to each other it is more difficult to determine pressures continuously over the entire length of the urethra.

Finally, the probe according to the invention comprises rounded walls even at the pressure measurement zones and its axial displacement is therefore facilitated thereby, which prevents injuries which are more or less painful for the patient when it is introduced into the urethra.

is According to a second embodiment of the invention, the device comprises a probe 10 constituted by a tube 11 pierced with a longitudinal duct or slot 12 communicating by its proximal end with a tube 14 connected to a fluid supply source and a means for measuring the pressure of the latter. A balloon is mounted on the tube and communicates with the duct. The structure of this balloon is borrowed from per se known balloon catheters. It is constituted by a tubular element 15, of length L, made from a material which is inelastic in the measurement area and biocompatible such as silicone. It is engaged around the tube 11 to which it is firmly fixed by its two ends. The tube 11 is pierced with an orifice 16 which places the duct 12 in communication with the annular space arranged between the tube 11 and the element 15. On inflation the balloon adopts an ovoidal form with a largest diameter a function of its volume. With a non-compressible fluid, water, it is possible to establish an accurate relationship between the variation in volume of liquid which is introduced into the balloon or withdrawn from it, and the variation of the latter's largest diameter.

1423 Additional ducts may of course be provided for filling the bladder and measuring the pressure inside it. An additional duct 121 opening into the balloon may also be added, to facilitate purge and pressure measurement.

A non-exhaustive example of the use of this device will be described below:

- Preparation of the device - the ducts are filled with water, the probe is connected by 121 to a pressure measurement element comprising a vertical tube open at its top end, a syringe is connected to the tube 14 and the operator adopts an elevated position compared with the level of the probe constituting the zero pressure reference, is the syringe is emptied into the balloon which slackens slightly; it is left connected. The pressure zero has thus been established: - the circuit is filled with water, - the lower pressure or depression applied to the balloon is expressed by a variation in level on the measuring instrument.

A graph is then plotted, associating the volume withdrawn from the balloon with its diameter using tubes of defined diameters.

- On the basis of this preparation the doctor may take measurements of compliance of the urethra, dilating the urethra to the desired diameters and recording the corresponding pressure of the fluid.

1423 On the basis of this first set of measurements taken for a given diameter of the balloon, one may determine what the compliance of the urethra is in the zone in which the pressure is maximum. For this purpose the balloon is positioned at the level of this zone and the pressure curve is plotted as a function of the different volumes, i.e. for different diameters.

Although what are currently deemed to be the preferred embodiments of the present invention have been shown and described, it will be evident that the person skilled in the art will be able to introduce different changes and modifications thereto without departing from the scope of the present invention as defined by the accompanying claims.

1423 12

Claims

1. Device for measuring urethral compliance, comprising a probe (1, 10) with a tube (2, 11) of diameter (D) pierced by at least one longitudinal duct (4, 5, 6, 12) and provided with at least one pressure pick-up means each communicating with its respective duct, a means of fluid supply of the said duct and a means of measuring the pressure of the said fluid, characterized in that the said pressure pick-up means comprises an annular element (Z1, Z21 Z3, 15) mounted on the tube, of convex profile in the active position of pressure measurement and the largest diameter of which is greater than the diameter of the said tube (2, 11).

2. Measuring device according to Claim 1, wherein the said pick-up means comprises an olive-shaped element, whose wall at the level of its largest diameter is pierced by an orifice (01, 02, 03) communicating with the said duct (4, 5, 6).

3. Device according to Claim 2, wherein the said element comprises a circumferential groove (R1, R2, R3) perpendicular to the axis of the tube, the said orifice opening into this groove.

4. Device according to one of Claims 1 to 3, wherein the tube is provided with at least one second annular element (Z2) communicating with a second duct and having a diameter (D2) different from the diameter (D1) of the first such annular duct.

5. Device according to Claim 4, wherein the second element is of smaller diameter than the first and is arranged behind the first with respect to the distal end of the tube.

1423 13

6. Device according to one of Claims 1 to 5, wherein it comprises at least three annular elements (Z1, Z2, Z3) each communicating with a different duct and equidistant from each other.

7. Device according to Claim 6, wherein the diameters of the said annular elements are of progressively decreasing size counting from the distal end of the tube.

8. Device according to Claim 1, wherein the pick-up means is constituted by a balloon communicating with the said duct.

9. Device according to Claim 8, wherein the balloon is made of a material which is inelastic in the pressure measurement area.

10. A device for measuring urethral compliance substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.

11. A device for measuring urethral compliance substantially as herein described with reference to Figure 5 of the accompanying drawings.