Although the present invention is useful in any adhesive composite needing a delivery system, it has particular benefit in connection with transparent film dressings and surgical drapes. These dressings and drapes are widely used as a protective layer over a wound, facilitating healing in a moist environment while acting as a barrier to liquids and bacteria. Dressings of this type are available under trade names such as Tegaderm.TM. (3M, St. Paul, Minn.), Bioclusive.TM. (Johnson & Johnson, New Brunswick, N.J.), Op-Site.TM. (T. J. Smith & Nephew, Hull, England) and Uniflex.TM. (Howmedica, Largo, Fla.).
The polymeric films used in such dressings are conformable. By this it is meant that these films are extremely thin, flimsy, and supple. They are supplied with a releasable protective liner overlying the adhesive coated surface of the film. When the liner is removed, the adhesive coated film tends to wrinkle and stick to itself interfering with the smooth aseptic application of the dressing or drape to the skin. Various delivery systems have been proposed to obviate this problem. PG,4
One such delivery system utilizes a removable frame to support the edges of the film during its application. U.S. Pat. No. 4,372,303 describes a composite having a relatively thin polymeric film which is conformable to animal anatomic surfaces. A pressure-sensitive adhesive is coated on one surface of the polymeric film, a release liner is attached to the adhesive coated surface of the film, and a frame is attached to the exposed surface of the film. In use the frame stays with the film until the film is affixed to the skin, at which time it is removed.
Another delivery system is described in U.S. Pat. No. 4,513,739. That patent describes a wound dressing comprising a film that is coated on one face with a biocompatible adhesive. One or more liner sheets are releasably adhered to the adhesive coated surface. Release retarding means are provided along one edge or a pair of opposed edges of the dressing to require a greater force to separate the layers (film, adhesive, and liner) at the edge or edges than at the remainder of the contact area. The release retarding means may be a thicker strip of the polymeric film, a stiffer piece of film adhered to the film at its edges, a strip of liner wrapped around the edge of the film and adhered to the exposed surface of the film, or a strip attached to the exposed surfaces of both the film and the liner. Alternatively, a more aggressive adhesive may be used at the edges than on the central portion of the dressing.
A third delivery system is described in U.S. Pat. No. 4,485,809. In this system, a window frame of liner material is provided for support during placement of the dressing by removal of a center section of the release liner. The window frame is then removed by separation of the film at the perforations provided within the area of the frame.
A fourth delivery system is used in the Veni-gard.RTM. dressing (Conmed, Utica, N.Y.). In this dressing, a permanently attached foam frame is provided on the non-adhesive side of the film backing.
An additional problem which occurs in the use of thin film adhesive dressings is the premature release of the dressing from the skin, generally initiated by failure of the adhesive at the edges of the dressing. Practitioners will occasionally secure the edges of the dressing with medical tape in order to avoid this problem. This is a very inefficient solution to the "edge lift" problem involving additional materials and time.