The pit does not have any magical properties. What turns the guac brown is the air. If you can keep air from touching the guac then it will stay green. The pit will keep a portion away from the air, but what is more affective is to put plastic wrap over it and push it right down onto the surface.
In my experience, denuded skin is when the top layer is off, sore is very superficial and usual caused from a shearing force. As above, there are many taypes of foam backed dressings used in teh VA, depending on which VA you are at. I am familiar Allevyn but here is a site where you can compare.
vaâ²por pres`sure. n. the pressure exerted by the molecules of a vapor. vapor pressure. 1. The pressure exerted by water vapor in the atmosphere. 2. The pressure exerted by a vapor on the solid or liquid phase with which it is in equilibrium. At pressures lower than the vapor pressure, atoms or molecules of the liquid or solid being vaporized can escape from the surface of the liquid or solid.