Surgery: splint – brace – or bandage – Bandage structure – Skin laceration or wound cover
Reexamination Certificate
2000-03-02
2001-12-04
Brown, Michael A. (Department: 3764)
Surgery: splint, brace, or bandage
Bandage structure
Skin laceration or wound cover
C602S041000, C602S042000, C602S043000, C602S044000, C602S045000, C602S046000
Reexamination Certificate
active
06326524
ABSTRACT:
BACKGROUND OF THE INVENTION
Adhesion to the body is a complicated process that is necessary to the functionality of a wide variety of products including but not limited to wound care dressings and ostomy appliances. It is known that adhesion to the skin for prolonged periods of time requires management of perspiration and other trans-epidermal water losses (TEWL). Pressure sensitive adhesives containing water-absorbing powders have been found effective in TEWL management. In particular, hydrocolloid adhesives are especially effective, and are preferred for this purpose.
It is common practice to manage wounds by covering them with a hydrocolloid wound dressing. These dressings typically consist of a pressure sensitive adhesive into which has been dispersed hydrocolloid particles. U.S. Pat. Nos. 3,339,546, 4,551,490, and others comprising the prior art of hydrocolloid containing pressure sensitive adhesives demonstrate this practice. Hydrocolloid wound dressings are exceptional in their ability to manage wound exudate. They achieve long wearing times, and provide a moist wound healing environment. This environment promotes autolytic debridement of the wound, non-traumatic dressing removal, and many other improvements over conventional adhesives and dressings that are believed to be beneficial to wound healing.
While hydrocolloid adhesives are known for the valuable characteristics described above, one limitation is their short-term rate of absorption. Typically the moisture absorbing capacity of a hydrocolloid adhesive is exceptional, and can exceed 5000 grams per square meter per day (gsm/d). However, absorption during the first hour is typically below 1000 gsm/d, and proportionally less at shorter times. As a result, hydrocolloid wound dressings are effective for a certain range of wounds, which produce light to moderate exudate. For heavily exudating wounds, the inability of hydrocolloid dressings to manage exudate leads to leakage of wound fluid sometime during the first 24 hours of wear.
For heavily exudating wounds, foamed polymers coated with a pressure sensitive adhesive on their wound contact surface are sometimes used. It is believed that their familiar design similar to strip bandages or gauze) and ability to absorb wound exudate relatively quickly are factors in their selection. However, these products suffer from several limitations. Unlike hydrocolloid wound dressings, these products are not noted for the preferred wound healing capabilities of hydrocolloid dressings. Further, they typically have limited long term absorbing capacity as their absorbency results primarily from a mechanical effect produced by the pores and cells of their foamed structure. Obviously, an additional limitation of conventional foamed dressings is that they will lose moisture when compressed. Finally, as the wound contact surface may be coated with a pressure sensitive adhesive to adhere to the body, the wound may be traumatized upon removal of the conventional foam dressing when that adhesive bonds to the healing wound itself.
As an ostomy device, a foamed hydrocolloid adhesive skin barrier offers several benefits over the state of the art. Flexibility of the skin barrier is greatly enhanced compared with a non-foamed barrier of the same composition. A secure attachment to the skin can be achieved, while reducing the removal force by virtue of the lessened contact area. As for wound dressings, intimate contact between hydrocolloid adhesives and the skin of an ostomate is well established as a beneficial attribute. Finally, the ability of the foamed structure to conform to irregular surfaces of the body to which an ostomy device must be attached is improvement over non-foamed adhesives.
SUMMARY OF THE INVENTION
The invention described herein improves the state of the art for hydrocolloid adhesives by changing the structure of the adhesive itself. Gas bubbles introduced into the pressure sensitive adhesive during the manufacturing process create a lightweight, cellular, two-phase structure. Properties of the foamed material depend on the individual properties of both the gas and solid phases. The size and extent of each phase are key characteristics in describing the structure of the foamed adhesive. In particular, the size and shape of cells in the gas phase determine the ultimate properties of a foamed structure for a given solid phase. Additionally, the density of the overall foamed structure can be useful for characterization. The structure of the foam may be open celled, with two or more cells connected by tunnels, or closed celled, where cells are predominantly isolated from one another.
Foaming hydrocolloid adhesives increases their flexibility and lowers the density and cost of the overall adhesive product. Creation of the foamed structure also results in an increase in surface area of the adhesive exposed to the contact surface. The increased surface area is particularly useful for adhesion to the body as it enables rapid absorption of liquids by a mechanical means. The time scale for absorbing liquids by physically trapping them in the cells of the foamed adhesive is significantly shorter than that for absorbing liquids chemically by the forces of attraction in the hydrocolloids themselves. Further, when liquids are trapped in the cells of the foam, the area of contact between the absorbed liquid and the solid phase of the adhesive is increased. As a result, a second, chemical based absorption process begins. These two processes work together to increase the overall absorption rate for a foamed hydrocolloid adhesive.
Depending on the size, shape, and extent of the cells, the foaming process can create a structure where a tortuous path of open cells and tunnels connects two exterior surfaces of a foam. In that case, moisture from one surface can rapidly be conducted to another surface. In the case of a wound dressing, this process can significantly enhance the overall rate and capacity for management of TEWL. Wound fluid quickly fills the cells of the foamed adhesive and is then conducted to another surface of the adhesive. If that surface is exposed to the atmosphere, the fluid can evaporate. If that surface is laminated with a film capable of transmitting moisture or moisture vapor, then wound exudate can pass through that film. In either case, fluid is managed at a faster rate and to a greater extent (capacity) than is possible using unfoamed hydrocolloid dressings. Extension of the concept of a foamed hydrocolloid adhesive to other kinds of body adhesion is clear to those skilled in the art. For example, improvements resulting from the foamed structure enable the adhesive to manage a greater quantity of perspiration generated at a faster rate than an unfoamed product. This improvement is useful in general for adhesion to the body, and in particular for wound dressings and ostomy appliances as cited above.
REFERENCES:
patent: 3797494 (1974-03-01), Zaffaroni
patent: 4292972 (1981-10-01), Pawelchak et al.
patent: 4775374 (1988-10-01), Cilento et al.
patent: 5429591 (1995-07-01), Yamamoto et al.
Bayless Richard F.
Fattman George F.
Bristol--Myers Squibb Company
Brown Michael A.
Hamilton Lalita M.
Krieger Stuart E.
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