WO2010139926A1

WO2010139926A1 - Hyperbaric dressing and method of manufacturing

Info

Publication number: WO2010139926A1
Application number: PCT/GB2010/000979
Authority: WO
Inventors: Melvin Frederick Vinton
Original assignee: Lnotec Amd Limited
Priority date: 2009-05-18
Filing date: 2010-05-18
Publication date: 2010-12-09
Also published as: GB2470358A; GB2470358B; GB0908507D0

Abstract

In a hyperbaric dressing (2) a first surface of an absorbent layer of material (6) contactable with damaged tissue (7) is secured to a central portion of an enclosing layer (4). The enclosing layer is impermeable to exudate and the absorbent layer can absorb exudate. A peripheral portion of the enclosing layer is adhesive (14), to adhere to skin (9) around the damaged tissue, with a second surface of the absorbent layer contacting the damaged tissue. The dressing comprises a conduit (8) for delivery of a fluid such as oxygen into the enclosure (5) thus formed beneath the enclosing layer. The conduit extends beneath an edge of the enclosing layer and is spaced from the damaged tissue, being held away from the damaged tissue by a portion of the absorbent layer. An advantage is that a cavity is formed in the absorbent layer to receive the conduit, the thickness of the absorbent layer being greater than the diameter of the conduit.

Description

HYPERBARIC DRESSING AND METHOD OF MANUFACTURING

This present invention relates to a hyperbaric dressing and methods for using and manufacturing a hyperbaric dressing.

BACKGROUND OF THE INVENTION

It is known that a supply of oxygen to a wound or through the skin covering a wound can be used to promote healing and to reduce scarring of damaged tissue. Typically, oxygen is absorbed by tissue fluids, thus improving the oxygen content of intercellular fluids and/or promoting metabolism and repair of the damaged tissue.

As such, there are numerous ailments which may benefit from the topical application of oxygen to damaged tissue, for example, osteomylelitis, tendon, ligament and cartilage damage, fractures, burns, scalds, necrotising fasciitis, such as pyoderma gangrenosum, pressure-induced decubitus (bed sores), venous and diabetic foot and leg ulcers, as well as cuts, abrasions and surgically-induced wounds and incisions.

In the healing process of non-infected wounds, low levels of exudate moisturising the skin surrounding a wound may be considered positive. When exudate becomes excessive or the wound becomes 'chronic' and non-healing or when infection becomes established, exudate may take on a different guise and has justifiably been termed 'a wounding agent in its own right' as it has the capacity to degrade growth factors. Excessive and particularly infected exudate from non-healing wounds may cause maceration to intact skin inhibiting the healing process. Mild maceration can be seen in the puffy whiteness to skin surrounding a wound when a 'sticking plaster¹ is removed.

Highly absorbent, non-hyperbaric dressings are known in the art such as 'island dressings' which contain absorbent foam material for contact with the wound, allowing exudate to be wicked away into the foam material. In such a dressing, a foam island may be fixed to a central portion of a liquid-impermeable enclosing layer. A peripheral portion of the enclosing layer encircling the foam is adhesive, so that when the foam is positioned over a wound, the adhesive layer sticks to the patient's skin and forms a seal around the wound to prevent exudate escaping the dressing. Soiled or leaking dressings are seen as poor nursing practice and are distressing to patients. A known attempt to combine the benefits of an absorbent dressing and a hyperbaric dressing requires a tube for delivering oxygen to be placed in the wound under a conventional absorbent material which is then overlaid with an occlusive (sealed) dressing. However, placing a tube in a wound is undesirable and problematic as the presence of the tube can be uncomfortable for the patient and physically disturb the wound, and because removal of the tube after treatment disturbs the granulation of new tissue. Furthermore, oxygen discharged directly into wound tissue raises the concern of oxygen embolism.

Consequently, there is a desire to provide a hyperbaric wound dressing which allows absorption of exudate whilst also allowing delivery of oxygen, without the means for delivering the oxygen adversely affecting the wound itself.

SUMMARY OF INVENTION

The invention relates to a hyperbaric dressing, a method of treatment for assisting the healing of damaged tissue and a method of manufacturing a hyperbaric dressing, as defined in the appended independent claims to which reference should now be made. Advantageous or preferred features are set forth in the dependent claims.

A hyperbaric dressing according to the present invention may advantageously comprise: an enclosing layer impermeable to a first fluid, such as wound exudate, for forming an enclosure around damaged tissue; an absorbent layer contactable with the damaged tissue, absorbent to the first fluid and arranged such that in use it is situated within the enclosure; and a fluid conduit for delivery of a second fluid, such as oxygen, to the enclosure. The fluid conduit is advantageously arranged such that it extends into the enclosure and is spaced from the damaged tissue. Spacing the fluid conduit from damaged tissue, such as a wound, may advantageously ensure that problems associated with the prior art method of placing an oxygen-delivery conduit or tube in, or in contact with damaged tissue are avoided.

Preferably, a cavity or slot may be defined within the absorbent layer, in which the fluid conduit is received. The cavity may be created by shaping the absorbent layer during manufacture or by cutting through the thickness of the absorbent layer. Alternatively, the cavity may be created by cutting to a pre-determined depth into the absorbent layer such that a step or depression is formed in a surface of the absorbent layer. Another form of cavity may comprise a tunnel which is completely enclosed on all sides by absorbent layer material.

In a preferred embodiment, the fluid conduit is held away from the damaged tissue by a portion of the absorbent layer. This could be achieved by positioning the fluid conduit such that it is sandwiched between the enclosing layer and the absorbent layer, thus being separated from the damaged tissue by the entire thickness of the absorbent layer. But this structure has the potential disadvantage that the presence of the conduit behind a part of the absorbent layer when the dressing is applied to a wound would make the surface of the absorbent layer in contact with the wound uneven. This may irritate the wound or cause discomfort to the patient, although this structure is an improvement on the prior art structure in which the conduit is placed directly into or in contact with the wound. If the absorbent layer is sufficiently thick and the conduit sufficiently small this structure may be acceptable. Alternatively, the absorbent layer may comprise a cavity shaped to receive or fit over or around the conduit within the dressing, as described above. In this case the thickness of the absorbent layer should be greater than the diameter of the conduit.

If the cavity does not extend through the entire thickness of the absorbent layer but is formed to a pre-determined depth into the absorbent layer, the conduit may be housed within the cavity such that it is separated from the damaged tissue by the remaining thickness of the absorbent layer beneath the cavity.

In a further alternative, the cavity is formed through the entire thickness of the absorbent layer and the conduit is secured within the cavity, spaced from the surface of the absorbent layer that will contact the wound. In a preferred embodiment this may be achieved by securing the conduit to the enclosing layer, at the base of the cavity.

In each case, the cross-sectional dimension(s) of the cavity, including in particular the depth of the cavity, may advantageously be greater than the corresponding cross- sectional dimension(s) of the conduit, such as its diameter if the conduit is a circular- section tube. This structure may advantageously avoid any contact between the conduit and the wound, or any application of uneven pressure due to the presence of the conduit (for example behind a part of the absorbent layer), as described above. -A-

In a preferred embodiment the depth of the cavity is equal to or greater than twice the corresponding dimension of the conduit, and particularly preferably equal to or greater than three times the corresponding dimension of the conduit. This may advantageously reduce the risk of contact between the conduit and the wound if the surrounding layer of absorbent material (which is desirably a soft, compressible material for protecting and avoiding damage to a wound) is compressed, for example during application of the dressing over a wound or if a compression dressing is used to cover the hyperbaric dressing, as described below.

In a preferred embodiment, the enclosing layer may comprise an adhesive surface. The enclosing layer extends beyond the periphery of the absorbent layer and the adhesive surface of this peripheral region of the enclosing layer may allow the enclosing layer to adhere to the surface around the damaged tissue and so to create the enclosure or headspace around the wound. The adhesion to the surface around the damaged tissue may create a seal against the outflow of wound exudate from the dressing. The creation of a seal may also allow a fluid such as oxygen, supplied through the fluid conduit, to accumulate in the headspace above the wound. The adhesive surface around the periphery of the enclosing layer may be exposable by the removal of a cover layer positioned over the adhesive surface in known manner.

Preferably, the adhesive surface extends over the entire surface of one side of the enclosing layer. The adhesive surface may then be used, preferably during manufacture of the dressing, to secure the fluid conduit and the absorbent layer to the enclosing layer. Thus, the fluid conduit may be secured by adhesion to the enclosing layer, such that an open end of the conduit is at a predetermined position, for example at a central point of the dressing. The conduit may then extend away from the predetermined position and across an edge of the enclosing layer. The absorbent layer may then be secured by adhesion to the enclosing layer, such that the cavity defined in the absorbent layer aligns with or fits over the conduit. The area of the enclosing layer is preferably greater than the area of the surface of the absorbent layer which contacts the wound, so that the absorbent layer forms an island surrounded by a peripheral region of the enclosing layer which may adhere to the skin surrounding the wound. When the dressing is in place over a wound, the conduit may extend from an edge of the dressing to permit delivery of the second fluid, such as oxygen, to the enclosure or headspace formed by the dressing over the wound.

As described above, dressings of this type are commonly used in treating severe, chronic or non-healing wounds such as leg ulcers, often in elderly patients. Although a dressing may have an adhesive surface around its periphery, it should not be assumed that an effective seal between the adhesive surface and the patient's skin can be achieved. The skin surrounding a chronic wound may have had many dressings stuck to it and then removed over a long period of time during treatment of the wound, and the skin is therefore likely to be fragile and in poor condition. Consequently, the design of a hyperbaric dressing must take into account the likelihood of a poor seal around its periphery; the application of the hyperbaric pressure to the enclosure beneath the dressing may also put stress on the adhesive bond between the dressing and the skin. It is therefore desirable to be able to use a compression dressing, covering the hyperbaric dressing, to hold the hyperbaric dressing in place. The compression dressing need not apply strong compression, but will apply some pressure to the outer surface of the hyperbaric dressing. It has been noted above that it is important that the fluid conduit of the hyperbaric dressing is held away from the damaged tissue of the wound and that the presence of the conduit in the dressing should not even make the contact between the surface of the absorbent layer and the wound uneven, as may be the case if the conduit contacts or presses against a rear surface of the absorbent layer, spaced from the wound. This problem arises because the conduit is typically more rigid than the absorbent layer. The use of a compression bandage or dressing covering the hyperbaric dressing, to hold the hyperbaric dressing in place, could clearly therefore lead to a problem if the application of pressure to the outer surface of the hyperbaric dressing presses the conduit against the wound or presses the conduit against a rear surface of the absorbent layer, such that the contact between the absorbent layer and the wound is made uneven. The design of the dressing of the present invention may advantageously address these problems.

In a further preferred embodiment, an opening or window is defined through the thickness of the absorbent layer, and the enclosing layer is transparent or translucent or comprises a transparent or translucent window portion aligned with the opening. Advantageously, such an opening may allow the wound to be observed without removal of the dressing (after the removal of any dressings, such as a compression dressing, covering the hyperbaric dressing). In addition, if the opening fills with exudate, the delivery of the second fluid, such as oxygen to the wound may be s observed through the production of bubbles within the enclosure around the damaged tissue. Preferably, the opening is located in a substantially central position of the dressing. However, there may be a plurality of openings through the absorbent layer. The cross-section of the opening(s) may be any shape including circular, square or star-shaped. 0

If the dressing comprises an opening through the absorbent layer, it is preferable for an end of the conduit to be positioned at the opening. This would allow for the clear passage of fluid from the fluid conduit to the wound surface and visual effects resulting from fluid delivery, such as bubbling, may be more readily observed. For this purpose,s the opening and the cavity (if present) in the absorbent layer are preferably continuous or contiguous.

In a preferred embodiment, the enclosing layer may be gas-permeable. This would enable the damaged tissue and the surface surrounding the damaged tissue, foro example the skin, to breathe. It is particularly advantageous for a portion of the enclosing layer which may adhere to the skin or other tissue to be gas-permeable, in known manner. The enclosing layer may comprise polyurethane or any other plastics material. 5 Although the enclosing layer is preferably gas-permeable, it is also advantageous that its permeability should be sufficiently low to enable a hyperbaric pressure to be generated within the enclosure beneath the dressing by the second fluid supplied through the conduit. Thus, the rate of supply of the second fluid, the desired hyperbaric pressure and the area of the dressing should be taken into account in0 selecting the gas-permeability of the enclosing layer. As noted above it should also not be assumed that the seal between the periphery of the dressing and the patient's skin is a perfect seal. A gas flow through the dressing may therefore advantageously occur. Gas is delivered through the conduit and diffuses out of the dressing through the gas-permeable enclosing layer, and may also leak through an imperfect seal with the skin. In view of these considerations the desired rate and pressure of the gas supply may be determined.

The first fluid preferably comprises exudate or any fluid released by damaged tissue 5 and it may comprise transudate. To aid in absorption of such fluids, the absorbent layer preferably comprises an open-cell material, such as foam, making it suitable for direct wound surface contact. It may comprise a surface layer designed for wound contact. The absorbent material is preferably able to wick away excess fluid from the site of tissue damage whilst allowing maintenance of low levels of exudate to enableo wound healing. Preferably, the enclosing layer does not allow the first fluid to exit the enclosure when in use, but it could comprise a means for allowing excess amounts of first fluid out, such as a perforation, for example for absorbtion by a separate dressing material. s The absorbent layer may comprise material which is permeable to both the first and second fluid. A gas-permeable absorbent layer may allow more efficient delivery of the second fluid to the damaged tissue by allowing diffusion or flow through the absorbent layer. An open-cell foam is suitable for this. o In a preferred embodiment, the absorbent layer may comprise material with an absorption capacity greater than or equal to 0.1 , 0.2, 0.3, 0.4, 0.5 or 0.6 ml/cm².

The second fluid preferably comprises oxygen to aid in the healing of tissue. Alternatively or additionally, the second fluid may comprise other beneficial reagentss such as cosmetic agents, anti-microbial agents, healing agents and pain-reducing agents, which may be administered constantly or periodically. In a preferred embodiment, the fluid comprising oxygen is deliverable at a rate of 5 to 25, 10 to 20 or most preferably 12 to 15 ml/hour. This is especially advantageous if the enclosing layer is breathable, such as if it comprises polyurethane. Oxygen delivery at such ao rate may be sufficient to overcome the breathability of the enclosing layer to maintain a suitable pressure in the enclosure or the headspace above the damaged tissue. A suitable pressure may be approximately 35 mm Hg (4.67 kPa), although this may vary depending on the size and nature of the wound and the corresponding size of the dressing. 5 A method of treating a human or animal to assist in the healing of damaged tissue, according to the invention, may advantageously comprise the steps of: applying a hyperbaric dressing as described above to the damaged tissue; and supplying the dressing with the second fluid.

A method for manufacturing a hyperbaric dressing according to the present invention may comprise the steps of: cutting or forming a cavity into an absorbent layer, absorbent to a first fluid; attaching a first surface of the absorbent layer to an enclosing layer; and inserting a portion of a fluid conduit, capable of delivering a second fluid, into the cavity such that it is spaced beneath a second surface of the absorbent layer distant from the enclosing layer. The steps of this method are not necessarily required to be carried out in this order. For example the conduit may be attached to the enclosing layer before or after or at the same time as the absorbent layer.

In a preferred embodiment, the method may further comprise cutting an opening or window through the absorbent layer. The opening may be cut such that it is continuous or contiguous with the cavity.

Preferably, the enclosing layer is attached to the absorbent layer by adhesion. Advantageously, the fluid conduit is attached to the enclosing layer by adhesion.

In an alternative aspect of the invention, the dressing may be fabricated by attaching the conduit to the absorbent layer, for example within a cavity formed or cut in the absorbent layer, and then attaching this assembly of the conduit and the absorbent layer to the enclosing layer.

SPECIFIC DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a view of the bottom side of a hyperbaric dressing according to an embodiment of the invention.

Figure 2 is a view of the top side of the hyperbaric dressing shown in Figure 1.

Figure 3 is a partial transverse section, on B-B of the dressing shown in Figure 1 , in use. Figure 4 is a partial transverse section on C-C of the dressing shown in Figure 1.

Figure 5 is a view of the bottom side of a hyperbaric dressing according to another embodiment of the invention. Figure 6 is a partial transverse section on D-D of the dressing shown in

Figure 5.

Figure 7 is a partial transverse section on E-E of the dressing shown in Figure 5.

Figure 8 is a side view of a dressing according to another embodiment of the invention.

Figure 9 is a side view of a dressing according to yet another embodiment of the invention.

Figure 10 is a view of the bottom side of a hyperbaric dressing according to an embodiment of the invention. Figure 11 is a partial transverse section on C-C of the dressing shown in

Figure 1 , in use.

A hyperbaric dressing 2, as shown in Figures 1, 2, 3 and 4 has an enclosing layer 4 impermeable to a first fluid, namely wound exudate, for forming an enclosure 5 around damaged tissue 7. The enclosing layer comprises a plastics material, polyurethane which is translucent or transparent. The enclosing layer also has an adhesive surface 14 on the side which faces the wound site 7. The adhesive surface is able to adhere to the skin 3 surrounding the wound to create a seal 9. The adhesive surface is exposed before the dressing is applied to the skin by peeling off a cover layer (not shown).

The hyperbaric dressing 2 also has an absorbent layer 6, comprising open-cell foam, which is contactable with the wound 7. It is absorbent to wound exudate. The surface area of the enclosing layer 4 is greater than that of the absorbent layer 6 and the absorbent layer is positioned centrally with respect to the enclosing layer such that an 'island' of absorbent layer is created. Consequently, in use, the absorbent layer is situated within the enclosure 5, as shown in Figure 3. A cavity in the form of a slot 10 is defined within the absorbent layer. The slot extends through the entire thickness or depth of the absorbent layer, and ends at an opening 12 through the absorbent layer. The opening is situated centrally within the absorbent layer and creates a window which is covered by the enclosing layer. In this embodiment, the absorbent layer has a surface area of approximately 100 cm² contactable with the wound and a thickness, before use, of approximately 3 mm. (Absorbent layers of other initial thicknesses, such as 4 mm, 5 mm or 6 mm, are also available and may also be used.) During use, the absorbent layer can swell significantly as it absorbs exudate, and increase substantially in thickness. The opening 12 is circular and has a diameter of approximately 8 mm and the slot is approximately 2 mm wide.

The hyperbaric dressing also comprises a fluid conduit 8 which is an open-ended tube. The tube is capable of delivering a second fluid, in this instance a gas, oxygen, to the enclosure 5. The tube is positioned within the cavity 10, 12 and adheres to the enclosing layer 4. The end or outlet of the tube 11 is positioned at the opening 12 of the absorbent layer. The tube thus extends into the enclosure when the dressing is in position over a wound.

In use, the hyperbaric dressing is applied over the wound such that the absorbent layer 6 contacts the damaged tissue and the enclosing layer 4 adheres to the skin surrounding the wound to create a seal 9. Figure 3 displays the dressing once it has adhered to the skin 3 surrounding the wound 7. (Figure 4 shows the dressing before the adhesive surface 14 of the dressing is pressed against the skin so as to adhere to the skin around the wound. Figure 11 shows a corresponding cross-section of the dressing after adhesion to the skin around the wound.) The creation of a seal around the wound allows the enclosure 5 to form. Oxygen is supplied to the enclosure through the tube 8. The oxygen source is not shown. The tube is spaced from the wound surface, as shown in Figures 3 and 4, by its adhesion to the adhesive surface 14 of the enclosing layer, advantageously avoiding the problems associated with directly contacting the tube with the wound such as the possibility of oxygen embolism and disturbance of granulation of new tissue when removed. The opening 12 allows the tube outlet 11 free space such that oxygen may be delivered directly to the wound surface. In addition, the characteristics of the wound may be observed through the window created by the opening. Advantageously, the positioning of the tube end 11 at the opening 12 may allow the observance of bubbling as the oxygen is delivered, thus acting as a visual cue to efficacy of the dressing. The oxygen is delivered a rate of approximately 12-15 ml/hour which is enough to overcome the breathability of the enclosing layer and obtain a pressure of approximately 35 mm Hg within the enclosure or headspace 5. The open cell foam of the absorbent layer 6 has an absorption capacity of approximately 0.64ml/cm². As the absorbent island has an area of approximately 100 cm², the island is intended to absorb and retain approximately 64 ml of exudate. Thus high levels of exudate may be wicked away from the wound s surface whilst retaining the ability to deliver oxygen to the wound site.

The absorbent material of the island increases substantially in thickness (in known manner) as it absorbs exudate. As the conduit is retained by adhesion in contact with the enclosing layer, and the diameter of the conduit is less than the initial thickness ofo the layer of absorbent material, the conduit is always held out of contact with the wound, even from the initial application of the dressing over the wound. Advantageously, as the absorbent material absorbs exudate and increases in thickness during use of the dressing, the enclosing layer and the conduit are raised further from the wound, ensuring that the conduit is spaced from the wound at alls times.

The dressing of this embodiment can conveniently be manufactured as follows. The enclosing layer is provided as a large sheet, with an adhesive surface on one side. A portion of the sheet is cut out to provide the enclosing layer 4 of the dressing. Theo absorbent layer is also provided as a large sheet, and a portion of the sheet is cut out to provide the absorbent layer 6 of the dressing. The absorbent layer is cut by a stamping operation using a shaped cutter. The cutter is shaped to cut not only the outer edge of the absorbent layer but also the cavity, including the slot and the opening. As the cavity extends through the thickness of the absorbent layer, it can be5 cut in the same operation as cutting the outer edge of the absorbent layer.

The absorbent layer and the conduit may then be stuck to the adhesive surface of the enclosing layer in order to form the dressing. 0 Figures 5, 6 and 7 show another embodiment of a hyperbaric dressing. Features similar to those shown in Figures 1 to 4 have been given like reference numerals. The hyperbaric dressing in Figures 5, 6 and 7 is substantially similar to that described for the embodiment shown in Figures 1 to 4 except that the slot or cavity 10 in the absorbent layer 6 does not span the entire thickness of the absorbent layer. This5 creates a step or depression in the upper surface of the absorbent layer, distant from the wound, on which the conduit tube may rest. The thickness of this step helps to space the tube from the wound site 7. The tube also adheres to the adhesive surface 14 of the enclosing layer 4 to secure the tube in place. The opening 12 extends through the full thickness of the absorbent layer and is centrally positioned but is square shaped rather than circle shaped.

Advantageously, as discussed above and as shown in Figure 7, the depth of the slot or cavity 10 cut into the absorbent layer is greater than the diameter of the conduit. This ensures that the presence of the conduit, which may be relatively more rigid, or less compressible or compliant, than the absorbent material, does not exert any additional pressure on the wound. This structure even prevents any risk of the conduit applying additional or uneven pressure to an upper surface of the absorbent material remote from the wound, which may be the case if the depth of the slot or cavity cut into the absorbent layer were less than the diameter of the conduit. The inventor's experiments have indicated that the types of wounds requiring treatment by topical oxygen therapy, which are serious wounds such as chronic, non-healing ulcers, are extremely sensitive even to small applications of uneven pressure, which can prevent or delay healing.

If the conduit is sufficiently flexible, or compliant, and/or the absorbent layer is sufficiently thick to avoid the presence of the conduit applying a localised pressure to the wound, a simpler structure may be used as follows. Figure 8 shows another embodiment of a hyperbaric dressing. Features similar to those shown in Figures 1 to 7 have been given like reference numerals. The hyperbaric dressing 2 does not possess a cavity in which the conduit 8 resides. Instead, the tube merely rests on top of the absorbent layer 6, sandwiched between the absorbent layer and the enclosing layer 4. The tube is separated from the wound by the full thickness of the absorbent layer.

Figure 9 shows another embodiment of a hyperbaric dressing. Features similar to those shown in Figures 1 to 8 have been given like reference numerals. The hyperbaric dressing 2 does not possess an opening through the absorbent layer 6. However, the absorbent layer 6 does define a cavity 10 in which the conduit tube 8 resides. The cavity 10 is a blind-ended tunnel completely enclosed within the absorbent layer and opening at an edge of the layer. As shown in Figure 9, the cavity is preferably of larger diameter, or cross section, than the diameter or cross section of the conduit. In use the tube delivers oxygen to the enclosure. Oxygen diffuses from the tube end 11 into the absorbent layer 6 which is open cell foam and so gas- permeable. The gas can therefore diffuse to the wound site 7. The tube is separated from the wound site entirely by absorbent material and not by adhesion to the enclosing layer. The tube is able to adhere to the enclosing layer 4 where it emerges from the edge of the absorbent layer.

Figure 10 shows yet another embodiment of a hyperbaric dressing. Features similar to those shown in Figures 1 to 9 have been given like reference numerals. A plurality of openings 12 are defined through the thickness of the absorbent layer 6. Two of the openings are not associated with conduits 8, and are merely present as windows to enable the wound surface to be observed. The four openings allow a greater proportion of the wound surface 7 to be observed. Conduit or tube ends 11 are positioned in the remaining two openings. Each tube 8 is positioned within a cavity 10, which is continuous with the respective opening 12. As with the embodiment shown in Figures 1 to 4, the cavity spans the entire thickness or depth of the absorbent layer and each tube is spaced from the wound surface 7 by its adhesion to the adhesive surface 14 of the enclosing layer 4.

Claims

1. A hyperbaric dressing comprising:

an enclosing layer impermeable to a first fluid, for forming an enclosure around damaged tissue;

an absorbent layer contactable with the damaged tissue, absorbent to a first fluid and arranged such that in use it is situated within the enclosure; and

a fluid conduit for delivery of a second fluid to the enclosure,

in which the fluid conduit is arranged such that it extends into the enclosure and is spaced from the damaged tissue, being held away from the damaged tissue by a portion of the absorbent layer.

2. A dressing according to claim 1 , in which a cavity is defined within the absorbent layer, in which the fluid conduit is received.

3. A dressing according to claim 2, in which the cavity is shaped to receive or fit over or around the conduit, the thickness of the absorbent layer being greater than the diameter of the conduit.

4. A dressing according to claim 1 , 2 or 3, in which the enclosing layer further comprises an adhesive surface.

5. A dressing according to claim 4, in which the fluid conduit is held away from the damaged tissue by adhering to the adhesive surface.

6. A dressing according to any preceding claim, which comprises an opening through the absorbent layer.

7. A dressing according to claim 6, in which the opening is located in a substantially central position of the dressing.

8. A dressing according to claim 6 or claim 7, in which an end of the fluid conduit is positioned at the opening.

9. A dressing according to any preceding claim, in which the enclosing layer is 5 gas permeable.

10. A dressing according to any preceding claim, in which the enclosing layer comprises transparent or translucent material. o

11. A dressing according to any preceding claim, in which the absorbent layer comprises open-cell foam.

12. A dressing according to any preceding claim, in which the absorbent layer comprises material with an absorption capacity greater than or equal to 0.1 , 0.2, 0.3,s 0.4, 0.5 or 0.6 ml/cm².

13. A dressing according to any preceding claim, in which the second fluid comprises oxygen. o

14. A dressing according to claim 13, in which the fluid comprising oxygen is deliverable at a rate of 5 to 25, 10 to 20 or 12 to 15 ml/hour.

15. A method for manufacturing a hyperbaric dressing comprising the steps of: 5 forming a cavity in an absorbent layer, absorbent to a first fluid;

attaching a first surface of the absorbent layer to an enclosing layer; and

inserting a portion of a fluid conduit, capable of delivering a second fluid, into0 the cavity such that it is spaced beneath a second surface of the absorbent layer distant from the enclosing layer.

16. A method according to claim 15, in which the enclosing layer is attached to the absorbent layer by adhesion. 5

17. A method according to claims 15 or 16, in which the fluid conduit is attached to the enclosing layer by adhesion.

18. A method according to claim 16 or 17, in which the enclosing layer has an

5 adhesive surface for, in use, securing the dressing to the skin of a patient, and the same adhesive surface is used for adhesion of the absorbent layer and/or the conduit to the enclosing layer.

19. A method according to any of claims 15 to 18 which further comprises cuttingo an opening through the absorbent layer.

20. A method according to claim 19, in which the opening is cut such that it is continuous with the cavity. s 21. A method of treating a human or animal to assist the healing of damaged tissue, comprising the steps of:

applying a hyperbaric dressing according to any of claims 1 to 14 to the damaged tissue; and o supplying the dressing with the second fluid.

22. A dressing substantially as hereinbefore described with reference to the accompanying drawings. 5

23. A method for manufacturing a hyperbaric dressing substantially as described herein.