GB2365342A

GB2365342A - Self-inflating medical apparatus

Info

Publication number: GB2365342A
Application number: GB0018817A
Authority: GB
Inventors: Christopher Leonard Watts
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-02
Filing date: 2000-08-02
Publication date: 2002-02-20
Anticipated expiration: 2020-08-02
Also published as: GB2365342B; GB0018817D0

Abstract

A medical device is described having a self-inflating characteristic. The device is illustrated in the form of a Foley catheter for draining urine from the body. The catheter comprises a tube 10 having a main drainage lumen 12, and an inflatable cuff 20 communicating with an inflation lumen 18. A self-inflation unit 42 is coupled to the proximal end of the inflation lumen 18 for forcing liquid into the cuff 20. The inflation unit 42 consists of an inner balloon 44 for containing the liquid, and an outer resilient member 46 within which the inner balloon 44 is received, for pressing on the inner balloon 44 to pump the liquid out of the inner balloon when a frangible seal 54 is broken. The inner balloon 44 is not substantially stretched when filled with liquid, so that there is very little risk of leakage through the wall material. The outer member 46 is stretched resiliently when the inner balloon 44 is filled, to provide the pumping force.

Description

<Desc/Clms Page number 1> SELF-INFLATING MEDICAL APPARATUS FIELD OF THE INVENTION This invention relates to medical apparatus having a self-inflating characteristic. The invention is especially suitable for use with an inflatable device insertable at least partly into the body, such as a drainage catheter, but it is not limited exclusively to such devices.

One particular aspect of the invention relates to a Foley catheter for draining urine directly from a patient's bladder.

DISCUSSION OF PRIOR ART Fig. I shows a typical "standard" Foley catheter assembly consisting generally of a tube 10 having a main drainage lumen 12 and urine entrance apertures 14 at the distal end 16 insertable into the bladder. In use, once the distal end 16 has been inserted, a sterile fluid (such as water, or saline) is injected from a syringe at the proximal end of the catheter, along an inflation lumen 18 to inflate an annular cuff 20 near the distal end 16. The inflated cuff 20 prevents retraction of the tube through the sphincter, and ensures that the distal end is located within the bladder to enable urine to drain through the main drainage lumen 12 to a urine collection device (not shown).

The "standard" Foley catheter does not have a self inflating characteristic. The proximal end of the inflation lumen 18 is closed by an inflation valve 22. To inflate the cuff 20, the needle of the syringe is inserted through the valve 22 to inject the sterile liquid along the inflation lumen 18. In order to deflate the cuff 20, the sterile fluid is withdrawn using an empty syringe inserted through the valve 22.

Fig. 2 shows a similar Foley catheter of a known type, having a self-inflation feature. Instead of using a syringe to inflate the cuff 20, an additional inflation balloon 24 is provided at the proximal end of the tube 10. The inflation balloon is made of an elastic material, and is provided with an inflation valve 26 (similar to the valve 22 described above) and with a frangible plug 28. Initially, sterile fluid is injected into the balloon 24, to expand the elastic material of the balloon under the pressure and volume of the fluid. The plug 28 prevents the fluid from reaching the cuff 20, such that the balloon holds the fluid under pressure. In order to inflate the cuff 20, the nurse breaks the frangible plug 28, and the elastic material of the balloon contracts to pump the fluid along the inflation lumen 18 to fill the cuff 20, When it is

desired to deflate the cuff 20, the fluid can be withdrawn by inserting a syringe through the valve 26 as described previously for the "standard" Foley catheter.

The self-inflating Foley catheter potentially provides a significant improvement in ease of use compared to standard Foley catheter. However, a problem with the self inflating type is that, during storage, the fluid held in the expanded inflation balloon 24 tends to leak away through the elastic material, or around the frangible plug. The inflation balloon 24 collapses, rendering the product useless.

Several attempts have been made to overcome this problem, which is inherent in the elastic nature of the material being prone to fluid leakage when stretched. The attempts have been to overcoat the balloon 24 with a layer 30 (shown in phantom in Fig. 2)of polyvinylidene chloride, which is a well known barrier polymer used to resist the transpiration of water vapour and other gases. However, this has not proved to be a complete solution as the layer of polyvinylidene chloride is very prone to cracking, which allows leakage again to occur.

The present invention has been devised bearing the above in mind. SUMMARY OF THE INVENTION Broadly speaking, one aspect of the present invention is to separate the fluid retention characteristic and the elastic characteristic into two different layers, or portions, of the inflation unit.

In one particular aspect, the invention provides an inflation unit which comprises: a balloon made of a material which is flexible and is substantially impervious to water liquid and water vapour; and a resilient member around the balloon, and configured to bear resiliently on the balloon when the balloon is filled (or at least partly filled) with fluid.

Preferably, the balloon is made of a material which is not substantially stretchable. In other words, the balloon has a fixed capacity.

Even if the balloon is made of a resiliently stretchable material, it is preferred that the balloon has a natural capacity (without significant resilient stretching, e.g. less than 10%) able to contain the desired volume of inflation fluid.

By separating the fluid containment, and resilient stretching, functions into two different members of the inflation unit, the liquid leakage problems of the prior

art can be significantly reduced, leading to much greater permissible durations of storage (shelf life), and a reduction in the number of device failures.

If desired, the resilient outer member may be made of a material which does have at least some liquid (or water or water vapour) barrier characteristic. However, this characteristic will be affected detrimentally when the material is stretched. By using an inner balloon to contain the liquid, the liquid can be contained securely no matter how much the outer member stretches when in use.

DESCRIPTION OF THE DRAWINGS An embodiment of the invention is now described by way of example only, with reference to the accompanying drawings, in which: (Fig. I is a schematic drawing of a prior art "standard" Foley catheter); (Fig. 2 is a schematic drawing of a prior art self-inflating Foley catheter); Fig. 3 is a schematic drawing of an improved Foley catheter in accordance with this embodiment of the invention; Fig. 4 is a schematic exploded view showing how the inflation balloon of Fig. 3 is constructed; Fig. 5 is a schematic view similar to Fig. 4, but showing a detail of the final construction of the balloon; and Fig. 6 is a schematic view similar to Fig. 5, but showing the balloon in an inflated condition.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to Figs. 3 to 6, a Foley catheter 40 is illustrated as a preferred, but non-limiting, example embodiment of the present invention. Certain of the features of the catheter are standard, and are similar to those described above with reference to Fig. 2 of the drawings; where appropriate the same reference numerals are used to denote the same features as those described previously.

In particular, the catheter comprises a tube 10 having a main urine drainage lumen 12. One or more drainage apertures 14 are provided at the distal end 16 for allowing urine to drain through the main lumen 12. An inflatable cuff 20 is provided near the distal end 16, and this communicates with an inflation lumen 18 extending from the cuff 20 to a point towards the proximal end 32 of the catheter. The inflation lumen 18 may (as shown) extend within the wall of the tube 10 defining the main

drainage lumen 12, or it may be a separate tube or channel wihin the tube 10. These features are well known to the skilled man and need not be described here in any further detail.

An inflation unit 42 is coupled to the inflation lumen 18 for automatically inflating the cuff 20 when desired. In contrast to the prior art, the inflation unit 42 comprises: an inner inflation balloon 44 for containing an inflation fluid; and an outer resilient member 46 distinct from the inflation balloon 44. The resilient member 46 is in the form of a cover or sleeve within which the inflation balloon is received.

In this embodiment, the main purpose of the inflation balloon is merely to contain the inflation fluid in a leakproof manner. The material of the inflation balloon is not required to stretch to generate a pumping force itself. Instead, it is the outer resilient member 46 which stretches to provide the pumping force to pump the fluid to the cuff 20.

Therefore, it is preferred that the inner balloon 44 be made of a material which is substantially non-stretchable. A suitable material is, for example, MF Film produced by Cryovac of Milan, Italy, which has excellent barrier properties to prevent the leakage of liquids therethrough. Other suitable non-stretchable materials include Saranex (Dow Chemical), oriented PET, and nylon barrier packaging film.

The inner balloon 44 is dimensioned to have a natural capacity corresponding to the desired quantity of sterile fluid to be contained within the inflation unit 42. For example, the capacity might typically be of the order of 10 cm 3 . The inner balloon may, for example, be spherical, or any other desired shape. It is preferred, but not essential that the inner balloon 44 has one or more folds, or pleats, to enable it easily to be collapsed into a predeten-nined shape.

If desired, it is possible to make the inner balloon 44 from a material which is inherently stretchable, for example latex, polyurethane, silicone, thermoplastic elastomers such as Kraton (Shell Polymers). However, if a stretchable material is used, it is nevertheless preferred that the balloon 44 has a natural, or unstretched, capacity corresponding to the desired quantity of sterile liquid to be contained within the inflation unit 42, By configuring the inner balloon to be substantially unstretched when containing the sterile liquid, the problems of liquid leakage due to material stretching can be minimised.

The resilient outer member 46 may be made from any suitable material having the desired resilient characteristics to stretch when the inner balloon 44 is filled with

the sterile liquid, and to press on the inner balloon 44 to provide a compression force to pump the liquid out of the inner balloon 44 when the fluid is released. Suitable materials include, for example, latex, silicone, polyurethanes, and thermoplastic elastomers (TPEs). It will be appreciated that, since the outer member 46 does not have to have any liquid barrier property, the material may be porous, if desired. This vastly increases the range of available materials which could be used. Nevertheless, for optimum protection against liquid leakage, it might still be desirable in some applications to form the outer member 46 from a resilient material which presents at least a limited barrier to liquid transpiration.

Referring to Figs. 4, 5 and 6, the outer member 46 is secured to (or integrally attached to) the free end of the inflation lumen 18 and (as best seen in Fig. 4) forms a funnel shape for receiving the inner balloon 24.

The inner balloon 24 is formed separately and has an inlet 48 and an outlet 50, A filling valve 52 is sealed within the inlet 48, and a frangible seal member 54 is sealed within the outlet 50. The inner balloon 44 is inserted into the outer member 46 prior to filling (i.e. in its deflated condition). The inner balloon 44 is orientated such that the frangible seal member 54 is adjacent to the mouth of the inflation lumen 18, and the filling valve 52 is adjacent to the open end of the outer member 46. The open end of the outer member 46 is then sealed around the filling valve 52 to retain the inner balloon 44 in position, and to form a seal therearound.

Once the above assembly has been completed, the inner balloon 44 is filled with the desired amount of sterile liquid, such as sterile water, or saline. The sterile liquid is supplied from, for example, a syringe or other filling device inserted through the filling valve 52. As the inner balloon 44 fills, it expands to its natural filled shape. The outer member 46 stretches and expands resiliently to accommodate the swelling inner balloon 44. When the desired quantity of liquid has been injected into the inner balloon, the syringe (or other filling device) is removed. The liquid is trapped in the inner balloon 44 by the frangible seal member 54.

It will be appreciated that, in the filled condition, the liquid is held within the inner balloon 44, and the inner balloon 44 is not substantially stretched. This can reduce the risk of leakage of liquid through the wall of the balloon, and around the filling valve 52 and the frangible seal member 54. In contrast, the outer member 46 is stretched, and it is this member which bears on the inner balloon 44 to pump the

liquid out of the inner balloon 44 when the liquid is released. However, the stretched outer member 46 does not (primarily) have to contain any liquid.

In use of the catheter, when it is desired to inflate the cuff 20, the nurse simply manipulates the frangible seal member 54 to break the seal (as with the device described previously with reference to Fig. 2). The liquid is then forced out of the inner balloon 44 by the outer member 46 contracting from its stretched condition to a relaxed condition. The liquid is forced along the inflation lumen 18 to fill and expand the cuff 20. (In the illustrated embodiment, the resilient member 46 should be made of a material which is liquid impervious, as there is no seal between the inner balloon 42 and the outer member 46. Alternatively, an annular seal could be provided at the position indicated by numeral 56).

When it is desired to deflate the cuff 20, the nurse simply inserts the needle of an empty syringe through the filling valve 52, and withdraws liquid from the catheter. It will be appreciated that the invention, particularly as described in the preferred embodiment, can enable a self-inflating catheter (or other medical device insertable into the body) to be produced without the liquid leakage problems of the prior art. The device can be simple and straightforward to manufacture, yet be reliable in use, and have an extended shelf-life permitting the device to be stored for long periods without losing its ability to self-inflate.

It will further be appreciated that the foregoing description is merely illustrative of a preferred example of the invention, and that many modifications and improvements may be made within the scope of the invention. Features believed to be of particular importance are identified in the claims. However, none of the features described herein or in the claims are regarded as essential in the broadest aspect of the invention, and the Applicant claims protection for any novel feature or idea described herein and/or illustrated in the drawings whether or not emphasis has been placed thereon.

Claims

CLAIMS 1. A medical device insertable into the body and comprising a first inflatable portion to be inflated in use, and an inflation unit for containing a liquid for inflating the first inflatable portion, wherein the inflation unit comprises: a balloon for containing the liquid, the balloon being made of a flexible material; and a resilient member outside and distinct from the balloon, the resilient member being configured to be in a stretched condition to press on the balloon when the balloon contains the inflation liquid.
2. A device according to claim 1, wherein the device is a catheter, and the inflatable portion is located at or near a distal. portion of the catheter insertable into the body.
3. A device according to claim 2, wherein the inflatable portion comprises an inflatable cuff.
4. A device according to any preceding claim, wherein the balloon is dimensioned such that, in its filled condition, the balloon is not substantially stretched.
5. A device according to claim 4, wherein the balloon is unstretched when in its filled condition.
6. A device according to claim 4 or 5, wherein the balloon is made of a material which is not resiliently stretchable.
7. A device according to any preceding claim, wherein the balloon is made of a film comprising a layer of a barrier material which is substantially impervious to water and to water vapour.

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8. A device according to any preceding claim, wherein the balloon comprises a port sealed by a valve.
9. A device according to any preceding claim, wherein the balloon comprises a port sealed by a breakable seal.
10. A device according to any preceding claim, wherein the resilient member is sealed directly or indirectly to the balloon at at least one region.
11. A device according to any preceding claim, wherein the resilient member is made of a material which is substantially impervious to liquid at least when the material is in an unstretched condition.
12. A device according to claim 2, or to any claim dependent thereon, wherein the device is a Foley catheter.
13. A device according to claim 12, wherein the device comprises a first lumen for permitting the drainage of urine through the catheter, and a second lumen for supplying inflation liquid from the inflation unit.
14. An inflation unit for a self-inflating Foley catheter, the inflation unit comprising: a balloon for containing an inflation liquid, the balloon being made of a flexible material; and a resilient member outside and distinct from the balloon, the resilient member being configured to be in a stretched condition to press on the balloon when the balloon contains the inflation liquid.
15. A medical device insertable into the body, or an inflation unit for a medical device, the device or the inflation unit being substantially as hereinbefore described with reference to any of Figs. 3 to 6 of the accompanying drawings.