2. Placement of Foam
Sterile, open-cell foam dressing is gently placed into the wound cavity. Open-pore,
reticulated medical-grade foams are used as they are the most effective at
transmitting mechanical forces across the wound and provide an even distribution of
negative pressure over the entire wound bed to aid in wound healing (Vacuum
therapy in wound management 2001). There are two different types of foam
available, black (applied into the wound) or white (applied over the wound) (Vacuum
therapy in wound management 2001). Black foam, polyurethane ether (PU), has
larger pores, is lighter, easily collapsible and hydrophobic with a pore size of 400 to
600 mm. It is used when stimulation of granulation tissue and wound contraction is
required. White foam, polyvinylalcohol (PVA), is used for restricted formation of
granulation tissue, as it is denser with smaller pores, requires higher negative
pressures to collapse, and is hydrophilic (absorbs exudate) with a pore size of
approximately 250 mm. Embedded in the foam is a fenestrated evacuation tube,
which is connected to a computer-controlled vacuum pump that contains a fluid
collection canister. The amount of pressure applied will depend on which type of
foam is used, with the white foam requiring higher negative pressure as it is denser.