Surgery – Truss – Pad
Patent
1989-11-01
1991-12-31
Green, Randall L.
Surgery
Truss
Pad
604304, 604364, 424443, A61F 1300, A61F 1500, A61L 1500
Patent
active
050762656
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to hydrogel dressings, their use and their manufacture.
Traditional wound dressings usually comprise a fabric or felt of absorptive material such as a gauze in direct contact with the wound. Such dressings are normally covered in order to avoid or reduce bacterial contamination but are not efficient in this respect. They have the general advantage of absorbing exudate from the wound but on the other hand, tend to stick to the wound surface, thus inhibiting healing. Furthermore, removal of the dressing is commonly painful where such sticking has taken place.
More recently, hydrogels have been proposed as wound dressings. The high water content of the gel is particularly compatible with the exposed surface of the wound and healing is significantly enhanced. There is in general no tendency to stick to the wound so that removal of the dressing is relatively painless.
A particular feature of such hydrogel dressings has been that they are impermeable to bacteria and thus serve to maintain the sterility of the healing surface, whereas fabric dressings, being porous, tend to permit bacterial invasion. This has been a significant factor in the promotion of hydrogel sheets for use as dressings.
In general, hydrogel dressings, even though moist, are able to absorb a moderate amount of exudate from the wound. However, where excessive production of wound exudate is encountered, the absorptive capacity of the hydrogel may be exceeded. It has been proposed to use hydrogel granules adhered to a non-porous backing in order to enhance absorption of exudate. In promotional literature on such products great emphasis has been laid on the impermeability of the backing and the resistance to bacterial invasion. However, there is some tendency for the granular hydrogel to stick to the wound surface and require removal, thus hindering healing.
We have now found that the above problems may be combated particularly satisfactorily by using a dressing comprising a hydrogel in sheet form with capillaries passing through the sheet. Excess exudate may then pass through the dressing and can be absorbed by a suitable absorptive dressing or compress placed over the hydrogel. If the size and numbers of such capillaries are suitably chosen, it is possible to deal with excess exudate while avoiding the problem of bacterial invasion found with traditional porous dressings.
The invention thus provides hydrogel sheets for use as wound dressings, said sheets being provided with capillaries which permit wound exudate to pass through the sheets while not permitting bacteria to infect the wound.
The capillaries are preferably of such diameter that the forces drawing liquid through the dressing from the wound are adequate. If the capillaries are too narrow, proteins, cells and other solids will block the flow of liquid, although it has been observed that the capillary forces are unusually high due to the particular surface properties of the hydrogel. If the capillaries are too wide, the capillary forces will be insufficient to draw liquid from the wound and may permit bacterial invasion.
Furthermore, the initial requirement of the dressing is to permit or enhance removal of suppurating liquid from the wound. While this process continues and there is a positive flow of liquid away from the wound, bacteria will not be able to invade in a contrary direction. However, as the flow of liquid subsides, chains of protein material and cells will build up in the capillaries so blocking them and preventing bacterial invasion. Eventually, a sheet of new tissue will develop which will completely block bacterial invasion. It will be appreciated that the relatively small area represented by the capillaries will not have any significant effect on the ease of removal of the dressing.
In general, the total cross-sectional area of the capillaries should represent 0.5 to 3.0% of the area of the hydrogel sheet, preferably 1 to 2%, e.g. about 1.5%. The capillaries may, for example be spaced 5 to 20 mm apart, conveniently in longitudinal and tra
REFERENCES:
patent: 4341207 (1982-07-01), Steer et al.
patent: 4541426 (1985-09-01), Webster
patent: 4556056 (1985-12-01), Fischer et al.
patent: 4587284 (1986-05-01), Luissi et al.
patent: 4588400 (1986-05-01), Ring et al.
patent: 4655758 (1987-04-01), Ring et al.
Ed Geistlich Sohne A.G. fur Chemische Industrie
Green Randall L.
Prebilic Paul
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