WO1994021323A1

WO1994021323A1 - Topical hyperbaric device

Info

Publication number: WO1994021323A1
Application number: PCT/GB1994/000542
Authority: WO
Inventors: Evelyna Dyson Cantwell
Original assignee: Supra Medical Corporation
Priority date: 1993-03-23
Filing date: 1994-03-17
Publication date: 1994-09-29
Also published as: EP0690734A1; GB9305996D0; NZ262475A; AU6216594A; CA2158930A1

Abstract

The invention provides a topical hyperbaric device (1.20) for wound healing adapted to retain a charge of therapeutic gas over a treatment period comprising a gas diffusion resistant flexible and/or resilient sheet material (3.31) including an adhesive face adapted to affix to the skin, said adhesive face surrounding a treatment area (16.30), at least one release layer (4.23) disposed over said adhesive face, and a conduit (5.25) for the supply of the therapeutic gas to the treatment area; wherein either the sheet material is formed of a generally planar sheet (3) and the adhesive layer is disposed upon the peripheral underside portion of the sheet, said release layer (4) at least overlaying said adhesive face, or the sheet material (20) is in the form of an inflatable bag, and in that the adhesive layer is disposed upon the peripheral underside portion at least of the portion of the bag adjacent to the treatment area (30), the edge portion (24) further supporting an external pressure ring adjacent the treatment area independent of the adhesive layer, which ring allows pressure to be exerted toward the interface between the skin (28) and the adhesive layer (22) in use.

Description

TOPICAL HYPERBARIC DEVICE

The present invention relates to topical hyperbaric devices for treating wounds and lesions on a patient's body by bringing a therapeutic gas into contact with the area to be healed.

Hyperbaric apparatus for the treatment of open wounds and lesions by application thereto of a therapeutic gas such as oxygen, with or without pharmacologically acceptable additives, is generally known, for example from US-A- 5154697 and US-A-4801291. Specifically it has been discovered that the treatment of open lesions and wounds in a hyperbaric chamber with oxygen promotes granulation, raises capillary blood oxygen levels, and elevates the Redox potential thereby suppressing bacterial growth.

In the above-identified prior art, a collapsible topical hyperbaric apparatus is revealed comprising a shell defining a substantially closed internal chamber arrangeable between an expanded and a collapsed configuration, said shell having an opening therethrough communicating with said internal chamber, a ring within said internal chamber secured to said shell about said opening, said internal ring about said opening being capable of conforming to a shaped surface of the patient's body and adhering thereto, gas-introducing means for introducing a therapeutic gas into the internal chamber for expanding said shell from a collapsed to an expanded configuration and pressure relief means to control flow rate thereby to therapeutically treat a portion of the patient's body.

These arrangements were provided with strap means for securing the hyperbaric apparatus to the body so that the adhesive means retained a hermetic seal during the treatment period. Generally the means for securing the hyperbaric apparatus to the body is a strap or band, or other means of compressing the device onto the body.

As stated in the prior art a good seal between the skin adjacent the wound and the adhesive layer is important otherwise the oxygen or other therapeutic gas will tend to leak from the device.

Previously, especially in the prior art, it was thought necessary to provide for a through flow of therapeutic gas such as oxygen in order to achieve good therapeutic results. However, for reasons which are described below, this arrangement is now not only superfluous but counter¬ productive, since it tends to induce oxygen toxaemia caused by excessive exposure to hyperbaric oxygen, where oxygen is the therapeutic gas. Thus in the prior art devices a certain level of leakage was in fact permissible especially when the hyperbaric device was adhered to the skin without a strap or band to hold the same down. In practice in order to utilise the through flow device some means of circulating the oxygen is required and this means that the device is only utilisable in a hospital environment.

Good adherence of the device to the skin is also a function of the adhesive used. However, another important factor lies in the design of the chambers. If reference is made to Figure 3 of US-A-5154697 and Figure 4 of US-A- 4801291 it will be seen that once the hyperbaric device has been inflated with therapeutic gas, it is no longer possible to apply direct pressure to the sealing area. Thus, once the device has been positioned and inflated, further attempts to perfect sealing can only be effected by applying overall pressure to the inflated device rather than by specific point loading on a desired portion of the adhesive band. This situation becomes more important when lower volumes of therapeutic gas are available i.e. when no significant through flow of gas is envisaged after application, or when only a limited quantity of therapeutic gas is available.

One object of the present invention, therefore, is to provide an arrangement allowing said adhesive layer to be resealed during use without affecting the inflated sheet material adversely.

Morphologically the most beneficial effects of hyperbaric gas treatment, and particularly hyperbaric oxygen treatment, is the stimulation of endothelial cell proliferation and generation of new blood capillaries. New blood capillaries can in fact be seen by with naked eye during successful treatment as early as two days after the commencement thereof. These new capillaries are stimulated in mild hypoxia and in practice at pressures of up to 1.03 to 1.04 atmospheres for a predetermined period. Above and below this range of values the wound is not beneficially effected. Oxygen toxicity is a condition resultant from excess oxygen exposure and results in distortion of the Krebs cycle which directly or indirectly leads to degeneration of the endothelial cells and destruction of newly formed capillaries stimulated by the hyperbaric therapy.

Another aspect of the present invention is to be found in the requirement that whereas the wound area in the skin is exposed to therapeutic gas, unaffected areas are covered preferably by the adhesive layer. This allows the therapeutic gas to act directly on the wound area while also allowing the adhesive to overlay a maximum area of undamaged adjacent skin. Another object, therefore, is to provide a topical hyperbaric device which can be readily adapted to locate precisely over an irregularly shaped wound so that (a) the adhesion of the device to the skin is not unnecessarily impaired or reduced so that excess leakage of therapeutic gas is avoided.

It has recently become apparent that for neo- vascularization and wound healing, oxygen pressures of about 1.03-1.04 atmospheres are required rather than the 2-3 atmospheres previously used. Also, because of the problems associated with excess oxygen exposure, it is usual to treat patients for comparatively short periods, for example 20 minutes twice a day to about four hours once a day for up to four days with a three or four day rest period per week. Even so, some toxicity effects may be observed after eight weeks of such a regimen.

It follows that hyperbaric oxygen therapy requires a delicate balance between enough therapeutic gas to cause revasculisation etc. , and avoiding excess therapeutic gas exposure. It is therefore both unnecessary and unwise to provide for oxygen through-flow since this not only unnecessarily complicates the device and support surfaces associated with it, but also tends to increase oxygen toxaemia.

For these reasons a single charge of therapeutic gas such as oxygen is usually enough for therapeutic purposes so long as the adhesive skin adhesion is leak-proof. I a preferred arrangement means are provided to purge the applied device of ambient air.

It is also an object of this invention to provide a hyperbaric chamber which can be readily self-applied in the home if appropriate. To this end it is, in practice, necessary to provide an economic system which is readily applied by those who are essentially unskilled. This requires both an economic, readily self-applied chamber and a source of pressurised therapeutic gas such as oxygen in a readily hand-portable form. In practice, once a . 5 topical hyperbaric device has been removed the adhesive properties thereof are usually too poor for the device to be reaffixed. Thus it is usual to replace it with a new device.

Thus, the invention has a further object in the provision 10 of an assembly of a topical hyperbaric device with a hand- portable source of therapeutic gas such as oxygen, which assembly allows the topical hyperbaric device to be charged with a desired pressure (e.g. 1.4 atmos) without necessarily requiring the use of a pressure gauge. Of 15 course, a pressure gauge can be applied to a hand-portable gas cylinder and arranged such that 1.4 atmospheres can be readily read off from a desired value.

It is also an object of the invention to provide a topical hyperbaric device formed from a single gas diffusion 20 resistant flexible and/or resilient sheet material to achieve economy of manufacture and simplicity in use. Compositely, therefore, the prior art provides a topical hyperbaric device comprising a gas diffusion resistant flexible and/or resilient sheet material including an 25 adhesive face adapted to affix to the skin, said adhesive face surrounding a treatment area, at least one release sheet disposed over the adhesive face and a conduit for the supply of a therapeutic gas to the treatment area. The present invention is characterised in a first aspect in •30 that the sheet material is formed of a generally planar sheet and the adhesive layer is disposed upon the peripheral underside portion of the sheet, said release layer at least overlaying said adhesive face.

The sheet material may be formed with a blistered area to accommodate a predetermined volume of therapeutic gas without stressing the interface in use between the skin and the adhesive layer.

A second aspect of the invention is characterised in that the sheet material is in the form of an inflatable bag and in that the adhesive layer is disposed upon the peripheral underside portion at least of the portion of the bag adjacent the treatment area, the edge portion further supporting an external pressure ring adjacent the treatment area disposed upon the adhesive layer, which ring allows pressure to be exerted towards the interface between the skin and the adhesive layer in use.

In a third aspect of the invention there is provided an assembly of a topical hyperbaric device comprising a gas diffusion resistant flexible and/or resilient sheet material including an adhesive face adapted to affix the sheet material to the skin, said adhesive face surrounding the treatment area, at least one release layer disposed over said adhesive face, a conduit for the supply of therapeutic gas to the treatment area, and a readily hand- portable canister of therapeutic gas for operative inter¬ connection with said conduit.

A final aspect of the present invention is characterised in that the release layer extends over a major proportion of the treatment area prior to use, and wherein the wound shape is sized from the release layer or a gauging layer attached thereto prior to use, whereby the device adheres to the skin adjacent the wound so that the device adheres over as large an area of skin as possible.

The sheet material may optionally be formed into a bag with an opening defined by the adhesive means in the form of a ring for disposition about the treatment area. A moist dressing material may be disposed on a portion of the internal face of the bag which is opposed to the opening so that the dressing overlays the treatment area only in the substantial absence of hyperbaric pressure.

The adhesive means may be formed of a flexible/resilient sheet coated on both surfaces with an adhesive, for example a thin hydrocolloid having a thickness of 0.2 mm to 0.65 mm and preferably about 0.45 mm. The release sheet may be a silicone coated release paper for removal prior to adhesion to the skin.

In a preferred form of the invention the adhesive is double-sided and has the release sheet secured to one surface thereof. To the other surface is secured the inner edges of the flexible/resilient bag so as to secure a firm seal between the flexible/resilient material and the adhesive layer. Most preferably the bag is secured to the adhesive means adjacent the intended aperture to the treatment area, but is not secured over the whole outer area of the adhesive means. The adhesive means preferably extends therefore outwardly of its point of adherence with the bag, said adhesive means over this portion being covered by a second annulus so that the area around the aperture can be secured to the skin without direct contact therewith.

The present invention also seeks to improve upon prior art devices and to provide an economic alternative to the foregoing, by providing a topical hyperbaric device formed from a single operative sheet of flexible and/or resilient plastics material provided with adhesive to at least a portion of one face thereof. Accordingly in this aspect, the hyperbaric device in accordance with the present invention has the general conformation of a traditional bandage or wound dressing but is provided with means for the supply of a therapeutic gas to a treatment area. The devices of the present invention are economical to manufacture and because they utilise comparatively small volumes of therapeutic gas are particularly adapted for out-patient treatment which has hitherto not been generally available with the devices of the prior art.

The gas diffusion resistant flexible and/or resilient material is preferably a transparent plastics material such as polyalkylene or PVC sheet with an adhesive face over part or all thereof. Other materials utilised in the art for adhering bandages for wound dressings etc. are generally suitable for this. For example, they may comprise a thin hydrocolloid adhesive having a thickness of 0.20-0.60 mm (preferably 0.45 mm) backed by a 50μ polyalkylene film, such as polyethylene.

The adhesive may extend over all of the operative face of the sheet material, in which case a dressing material may be adhered to the portion of the adhesive face which forms the intended treatment area. The dressing may be a traditional multi-layer woven material or a pharmacologically acceptable foam material for example.

Either may be impregnated with a pharmacologically active material, for example an antiseptic, an antibiotic, or an anti-inflammatory preparation, and/or may be absorbent. The dressing may be moistened with sterile water or saline solution. Alternatively the dressing may be a medicated alginate dressing as known in the art. Very often the dressing is not necessary.

The release layer is an essentially non-adhesive layer which forms a weak bond with the adhesive disposed on the sheet material. The release layer may be formed in a two or three layer partially overlapped configuration whereby the removal of one such layer allows a portion of the adhesive face to be exposed for contact with the skin about the wound. This arrangement allows the device to be correctly orientated relative to the wound and secured in this orientation while the other release layer or layers are removed so that the device is correctly orientated on the skin without folds or rucks.

The flexible and/or resilient sheet material is preferably transparent and may be planar, or may be formed by non- elastic stretching or thermo-forming with a pocket over the treatment area to retain a dressing therein, or merely to provide a greater area for the containment of therapeutic gas. In such an arrangement where the dressing is not present, the adhesive does not extend over the treatment area.

The conduit for the supply of therapeutic gas is connected between the treatment area of the device and a canister of the therapeutic gas. It is sealed into the treatment area in a gas tight fashion, optionally by the use of an adhesive filler such as a clear silicone filler.

In a preferred form of the invention the conduit is comprised of a length of a flexible transparent pharmacologically acceptable plastics tubing, for example Trygon (Registered Trade Mark), R-3603. In such an arrangement an aperture is formed in the sheet material in the treatment area, the end of the conduit is passed through said aperture and the conduit is secured to the exterior face of the sheet material by means of a secondary layer of an adhesive sheet material disposed over the conduit and adjacent portions of the exterior face of the sheet material to secure the conduit. In order to ensure a fluid-tight seal it may be necessary to coat the exterior of the conduit with a secondary adhesive layer such as a silicone adhesive.

One of the reasons that hyperbaric therapeutic gas devices have been restricted in use is that the cylinders of therapeutic gas tend to be heavy and require man-handling to the bedside. Alternatively sophisticated conduiting is required in a hospital to deliver the therapeutic gas to the bedside. This has necessitated the utilisation of a hospital bed for hyperbaric treatment.

The devices of the present invention are suitable for use in out-patient departments because the applicants also provide a readily hand-portable therapeutic gas cylinder for utilisation with the hyperbaric device of the present invention.

The hyperbaric gas is usually oxygen, but may be other gases, for example an inert gas such as nitrogen, and may comprise other additives if therapeutically indicated.

The hand-portable canisters in accordance with the present invention may be a one-shot canister with an outlet adapted for interconnection with the conduit and means being provided to release pressurized therapeutic gas in the one-shot canister at least to the conduit. There is sufficient gas in the one-shot canister to fill the treatment area once. The conduit may then be tied to prevent gas seepage, or the device may be provided with a one way valve or clamp to the same end.

Further, the canister or other device may be provided with means to supply the therapeutic gas to a treatment area at a predetermined pressure value, for example 1.03- 1.04 atmospheres. This may be effected by including a pressure responsive layer in the device which changes colour with changes in pressure.

In a preferred form of the invention the sheet material is provided with a closeable vent, the vent may comprise at least one aperture and preferably a plurality of small apertures formed, for example, by laser drilling, and overlaid to the desired extend with a gas diffusion vent layer, whereby temporarily pealing back the vent layer allows gas to escape from the device.

This arrangement allows ambient air from the affixed device to be vented to the exterior prior to use and for limited purging of the device with the therapeutic gas before the gas pressure is increased to operational values. With the correct selection of adhesives for the vent layer it can be arranged that the vent layer will separate from the sheet material in use if the interior pressure of therapeutic gas exceeds a preset value. This provides a means for protection against inadvertent over- pressurisation and hence the formation of leakage path between the skin and the overlaying adhesive layer as will be formed by excessive internal pressures, may be avoided.

Alternatively the therapeutic gas canister may be of the multi-shot type, in which case a pressure actuated valve on said canister may be utilised to control the therapeutic gas supply and preferably its pressure via the conduit to the treatment area. Alternatively the vent arrangement alluded to above may be used. Again, means may be provided to prevent seepage of the gas via the conduit in use when the canister is removed. This may, as previously stated, be effected by means of clamps, tying or by means of the use of one way valves within the device.

The devices according to the invention may be provided with a moisture indicator within the device; such a moisture indicator being secured within the device or attached to the dressing so that it changes colour as it dries. This enables the dressing, where used, to be replaced or re-moistened as necessary. The devices of this invention are useful in the treatment of conditions such as leg ulcers, wounds, post-operative lesions/wounds,haematomas, burns, skin grafts, sports injuries and frost bite. Specific conditions successfully treatable by the devices in accordance with the present invention include osteomyelitis, burns and scalds, necrotizingfaciitis, pyoderma gangreneosum, refractory ulcers and diabetic foot ulcers.

Of these pyodermic gangreneosum responds dramatically to hyperbaric therapy.

The devices according to the invention may be configured in any convenient size, for example from about 1 cm in diameter or diagonal, to body sized dependent on the intended treatment. The device may be designed to cover a square, rectangular, ovoid or circular or irregularly shaped treatment area as desired.

One aspect of the present invention is also directed to devices in accord with the present invention incorporating a secondary gas cushion. Such a gas cushion is adapted to protect the device when the same has been applied to an area such as an elbow, knee or heel against inadvertent knocks.

According, therefore, to a further feature of the invention there is provided a secondary gas diffusion resistant layer overlaying the primary gas diffusion resistant layer, said secondary layer being formed of a flexible and\or resilient sheet material secured about said primary layer by an adhesive facing, said secondary layer being provided with a secondary conduit for supply of a gas, optionally a therapeutic gas, after or simultaneously with, the supply of the therapeutic gas to the treatment area.

The device may comprise means, for example an LCD chip or a pressure-activated strip material which changes colour or form on an increase in pressure; thereby to indicate a maximum fill condition, or to indicate that further therapeutic gas is required.

The invention will now be described, by way of illustration only, with reference to the accompanying drawings wherein:

Figure 1 shows a vertical cross-section through a device of the invention from a first direction, Figure 2 shows a vertical cross-section through a device of the invention from a second direction,

Figure 3 shows a vertical cross-section through a device according to Figure 1 in situ over a lesion, Figure 4 shows a vertical cross-section through a device in accordance with Figures 1 and 2, but incorporating a one-way valve,

Figure 5 shows a diagrammatic side view from above of a rectangular device according to Figure 1.

Figure 5A shows a cross-section through the vent portion of Figure 5, Figure 6 shows a vertical cross-section through another device according to the invention;

Figure 7 shows a vertical cross-section through the devices of Figure 6 inflated over a lesion, and Figure 8 shows a plan view from below of the device as shown in Figure 6 prior to removal of the release sheet.

With reference to Figures 1 to 5 of the accompanying drawings a topical hyperbaric device (1) is provided with a flexible plastics transparent sheet material in the general form of a rectangle or square having a dimension of 100 mm. The sheet material (3) is formed over the entirety of its lower surface with an adhesive layer, whereas the upper layer is essentially non-adhesive. Centrally disposed on the underside of the sheet material (3) is an optional dressing (11) formed of a foamed material moistened by sterile water and\or with a pharmacologically acceptable alginate.

To the underside of the edges of the sheet material (3) is applied a primary release layer (4) which is secured to the adhesive underside of the sheet material (3) and generally conforms to the exterior periphery thereof.

However, in the arrangement as shown in Figure 1 the edge portions of the primary release layer (4) do not adhere to the edge portions of the underside of the sheet material (3) but are left free. A secondary release layer (10) is secured to each parallel edge of the sheet material (3) .

With reference particularly to Figure 2 it will be noted that the dressing (11) is pierced by the end of a conduit (5) which extends between the valve (6) of canister (2) to the treatment area (16) . The conduit (5) is secured to the exterior face of the sheet material (3) by means of an overlay (7) preferably formed of the same material as the sheet material (3) with an adhesive underside thereon.

The overlay (7) secures the conduit (5) to the exterior face of the sheet material (3) in a fluid tight fashion. In order to reinforce the fluid tight effect an adhesive silicone filler may be applied to the exterior of the conduit prior to adhesion of the overlay (7) to ensure that the conduit is truly secured and that no gas seepage can occur.

In an alternative form of the invention the arrangement of Figure 2 is repeated but the dressing (11) , when present, is cut away over a portion so that a one way valve (14) may be inserted to prevent seepage of the oxygen in the reverse sense within the conduit (5) . The one way valve (14) may be a flexible sheet secured to the under adhesive face of the sheet material (3) but provided with an opening which is securely closed by means of gaseous back pressure. A general arrangement of the device is shown in Figure 5 which shows the device connected diagrammatically to a hand-portable therapeutic gas cylinder wherein the valve (6) has yet to be operated such that the hyperbaric device (1) lies flat upon a flat surface.

With reference particularly to Figure 3 the hyperbaric device in accordance with the present invention is shown in diagrammatic form in situ upon the skin. Initially hair is removed from about the wound site so that the adhesive face of the sheet material (3) can firmly adhere to the skin in a fluid-tight fashion. The device, as shown in Figure 1, is then presented to the wound (13) in the skin (12) and positioned generally thereover. It will be appreciated that, as shown in Figure 1, the transparent sheet (3) and the release layers (4, 10) result in an arrangement where it is not possible to be sure that the device is correctly orientated. For this reason a gap (15) is left in the device between the peripheral edge of the dressing (11) and the inner edge of the release layer (4) . Since this gap (15) is transparent it is possible to ensure that the device is correctly orientated. With the device held in position from one end, one of the release layers (10) may be removed and the edge of the release layer (4) folded back so that an adhesive edge of the sheet material (3) may then be correctly orientated upon the skin. When this has been pressed into firm adherence, the release layer (4) and the remaining release layer (10) are stripped away such that the sheet material (3) adhesively overlays undamaged skin without rucks, creases or gas releasing discontinuities.

With the device (1) located over the lesion (13) on the skin (12) the conduit (5) is connected to the valve (6) of the canister (2) . The valve (6) is actuated to allow sterile oxygen to pass into the treatment space (16) whereby the dressing is raised from the lesion (13) . With a one-shot canister (2) there is always the possibility that the oxygen provided will exceed the volume of the treatment space (16) without raising this area to too high a pressure. For this reason an operational vent (8) may be incorporated as shown in Figures 5 and 5A. Vent (8) comprises a plurality of laser drilled apertures (8A) through the sheet material (3) and an adhesive resealable vent layer (8B) which can be manually lifted and replaced. This allows the device to be purged of ambient air after fixing and prior to final charging with oxygen.

Where a one-shot canister (2) is utilised it may comprise a valve which is operated by manual pressure and hence it is possible to inflate the treatment space (16) to the required degree and to top up as required for a single use of the device. A multi-shot canister can also be used for more than device and is similarly designed.

It is sometimes desirable that the dressing should be moist and should be provided with suitable therapeutic adjuncts for the treatment of the lesion concerned. Alternatively, a desired level of moisture may be incorporated in the therapeutic gas.

In a further form of the invention an external pressure ring, not shown, is interposed between the sheet material (3) to which it adheres at its periphery. The release layer (4) overlays the pressure ring which is adhered to its underside.

The pressure ring is provided with a generally central aperture and a plurality of concentric markings to assist wound profiling. In use the wound shape is cut from the combined pressure ring and release layer, the orientation of the device checked on the patient, and then the release layer is removed and the adhesive face of the pressure ring adheres to the skin as would the adhesive layer in the earlier described embodiment.

Turning now to Figures 6 to 8 of the accompanying drawings, there is provided a second form of hyperbaric device provided optionally with an internal dressing. With particular reference to the topical hyperbaric device (20) there is provided a flexible PVC sheet having a generally rectilinear configuration as shown in Figure 8. The PVC sheet is essentially flexible although it has a degree of resilience and in this case is a 4400 grade cadmium and lead-free di-decyl phthalate plasticized calendered PVC of a type generally used for urine bags. The PVC sheet (21) encloses a hyperbaric space (30) but is, in its pre-use condition, generally flat and enclosed within a sterile package.

The PVC sheet material (21) may optionally be formed internally with a generally square dressing (27) which is of the alginate type and retains a desired amount of sterile water. The lower portion of the sheet material (21) is formed with a central aperture (31) . The lower faces of the PVC sheet material are pressed into contact with a double-sided adhesive layer (22) to which they are firmly secured. The outboard edges of the double-sided adhesive layer (22) are also covered with a release layer (23) so that the outer portions of the double-sided adhesive layer (22) do not adhere to the outer lower edges of the sheet material bag (21) .

A release sheet (23) overlays the double-sided adhesive layer, said release sheet being a silicone-coated release paper in accordance with the known prior art. The double- sided adhesive layer (22) has an adhesive of a thickness of about 0.6 mm overlaying a central polyalkylene or PVC film.

With particular reference to Figure 8, the release sheet (23) which overlays the double-sided adhesive layer (22) is also provided with a target grid (33) printed thereupon.

Similar to the arrangement as shown in Figures 2 and 4 , Figures 5 and 6 are provided with a conduit (25) to admit hyperbaric oxygen. Said conduit is secured to the outer upper face of the material (21) by means of a conduit overlay (26) carefully secured as previously described before.

In use the release layer (23) which should be transparent and/or at least translucent is temporarily withdrawn from the device (20) and placed over the wound or the lesion. The release layer (23) is provided as shown in Figure 8, with a target grid and from this grid it can be readily seen where the lesion is relative to the aperture (31) . A paramedic can then draw an outline of the wound on the release sheet relating its centre to the centre of the grid (33) whereupon the release sheet (23) is once more laid upon the double-sided release layer (22) . With this lightly adhered thereto the paramedic may then cut round the wound site so that the aperture formed in the device (20) corresponds to the edges of the wound or lesion to which it is to be applied. The remaining portions of the release sheet are then removed and the device located over the wound or lesion. This is assisted because the PVC material (21) is transparent so that the wound can be accurately aligned with the aperture formed for it. The portions (24) are then pressed firmly into contact with the skin (28) about the lesion so that the formed aperture (32) is about the wound.

Hyperbaric oxygen is then introduced via conduit (25) from a hand portable oxygen cylinder (2) so that the device formed the shape somewhat as shown in Figure 6. Care must be taken not to overinflate the device since this may put an undue strain on the adhesive bond between the skin (28) and the device (20) . However, with the hand portable device it is possible to top up the hyperbaric pressure as necessary to a value usually of about 1.03 to 1.04 atmospheres.

Devices in accordance with the present invention may be applied such as to reduce hypoxia but avoid oxygen toxaemia. Typical regimens of 20 minutes twice a day, to 4 to 6 hour treatments for 4 days of a week allow wounds and other lesions to cure quickly.

It will be appreciated that because the therapeutic gas canisters are hand-portable, and because the devices in accordance with the present invention are essentially disposable, the assemblies in accordance with the present invention may be utilised on an out-patient basis and even applied and utilised by motivated patients on some occasions without professional medical intervention. Accordingly the arrangements of the present invention are cheap enough and easy enough to use to bring hyperbaric treatment more widely into use.

The invention provides, therefore, a topical hyperbaric device and an assembly of a topical hyperbaric device with a readily hand-portable canister of therapeutic gas such as oxygen.

Claims

C L A I M S

1. A topical hyperbaric device adapted to retain a charge of therapeutic gas over a treatment period comprising a gas diffusion resistant flexible and/or resilient sheet material including an adhesive face adapted to affix to the skin, said adhesive face surrounding a treatment area, at least one release layer disposed over said adhesive face, and a conduit for the supply of the therapeutic gas to the treatment area; characterised in that the sheet material is formed of a generally planar sheet and the adhesive layer is disposed upon the peripheral underside portion of the sheet, said release layer at least overlaying said adhesive face.

2. A device according to Claim 1 wherein the sheet material is formed with a blistered area to accommodate a predetermined volume of therapeutic gas without stressing the interface in use between the skin and the adhesive layer.

3. A topical hyperbaric device comprising a gas diffusion resistant flexible and/or resilient sheet material including an adhesive face adapted to affix to the skin, said adhesive face surrounding a treatment area, at least one release layer disposed over said adhesive face, and a conduit for the supply of therapeutic gas to the treatment area; characterised in that the sheet material is in the form of an inflatable bag, and in that the adhesive layer is disposed upon the peripheral underside portion at least of the portion of the bag adjacent to the treatment area, the edge portion further supporting an external pressure ring adjacent the treatment area independent of the adhesive layer, which ring allows pressure to be exerted toward the interface between the skin and the adhesive layer in use.

4. A device according to Claim 3 wherein the adhesive layer is formed on a double-sided web, said release layer adhering to a first side of the web, and said pressure ring adhering to the second side.

5. A device according to any preceding Claim wherein the release layer extends over a major proportion of the treatment area prior to use, and wherein the wound shape is excised from the release layer or a gauging layer attached thereto prior to use, whereby the device adheres to the skin adjacent the wound without exposing more than a predetermined amount of undamaged skin to hyperbaric treatment.

6. A device according to any preceding Claim wherein the flexible and/or resilient material is a transparent plastics material, and the adhesive face is disposed over part or all thereof.

7. A device according to any preceding Claim wherein the adhesive layer is a hydrocolloid adhesive having a thickness of 0.2 to 0.6 mm backed by a 25μ to 75μ. polyalkylene film.

8. A device according to Claims 1 or 2 wherein a dressing material is disposed within the device and adapted in use to contact the treatment area, and wherein said adhesive extends over the whole operative face of the sheet material in part to secure the dressing material to an adhesive face thereof.

9. A device according to any preceding Claim wherein the release layer is a weakly adhesive layer forming a weak bond with the adhesive disposed in the sheet material.

10. A device according to any preceding Claim wherein the release layer is formed of two or three layers in a partially overlapped configuration, whereby removal of one such layer allows a portion of the adhesive face to be exposed for contact with the skin about the wound.

11. A device according to either of Claims 1 or 2 wherein the sheet material is transparent and either planar, or formed by non-elastic stretching or thermo-forming with a pocket over the intended treatment area.

12. A device according to any preceding Claim incorporating a secondary gas cushion adapted to protect the device when the same has been applied to an area likely to be subject to inadvertent pressures.

13. A device according to any preceding Claim further comprising a vent means wherein at least one aperture is formed in the sheet material and wherein a resealable adhesive layer is applied thereover to reversibly obturate the said at least one aperture to allow purging of the in situ device.

14 An assembly of a device according to any preceding claim and a canister for therapeutic gas therefor, wherein the conduit for the supply of the therapeutic gas is connectable between the treatment area of the device and said canister.

15. An assembly according to Claim 13 wherein a remote end of the conduit is interlocked with a readily hand-portable canister of a therapeutic gas.

16. An assembly of a device with a pressurized canister of therapeutic gas according to any preceding Claim, wherein the therapeutic gas is medical grade oxygen.

17. A device or assembly according to Claim 15 wherein the canister or the hyperbaric device is provided with means for pressure controlled supply of gas to the treatment area.