The most common complications of Negative Pressure Wound Therapy are maceration of skinand eczema etc.
There would be overgrowth of granulation tissue if the foam is covered over the wound for toolong, which may cause bleeding of wound and damage to the tissue in removal of foam.
It may cause infection if there were residual foam left in the wound tissue.
Bleeding or even skin necrosis for lack of blood would happen if the setting of negative pressurewere not appropriate.