Interface dressings influence the delivery of topical negative-pressure therapy

Background: Topical negative-pressure therapy is a widely used wound management system that generates a negative pressure at the wound surface through a foam pad, which aids in wound stimulation through mechanical forces on the wound bed. System guidelines state that the foam dressing should be placed in direct apposition with the wound surface; however, an interface dressing is often inserted at this point to promote comfort at dressing changes. Methods: Topical negative-pressure dressings were applied to 40 healthy volunteers. Pressures at the skin surface under the dressing were recorded and compared with those measured by a topical negative-pressure machine using the Therapeutic Regulated Accurate Care pad system. These were repeated, inserting different types of interface dressings: petroleumjelly (Vaseline)-impregnated gauze, nonadherent silicone dressing, and mylar polyester film dressing. Results: Pressures recorded at the skin interface with no interface dressing were close to those set on the topical negative-pressure machine (mean pressure change, -5.11 +/- 0.55 mmHg). Interposition of dressings at the skin/ foam inter-face affected pressure transmission through the foam, and some caused significant decreases in pressures recorded at the skin surface (e.g., Vaseline-impregnated gauze: mean pressure change, -11.76 mmHg; maximum pressure change, -41 mmHg). Conclusion: The loss in negative pressure means that pressures designated by the machine cannot be relied on as a measure of wound pressure when certain dressings are used at the interface. This could be important in determining the outcome of some wounds under topical negative-pressure therapy treatment.