From EP 0 620 720 B1 it is known that a wound insert, which consists of an open-cell polymer-foam, should be placed on the wound surface. The wound surface and the wound insert are sealed over with a cover that is sealingly secured to the skin surrounding the wound surface. A vacuum can be created under the cover using a suction tube in order to vacuum tissue fluids out of the wound. The polymer-foam exhibits a relatively small pore size in order to prevent in-growth of wound tissue into the wound insert. The small-pored foam may become clogged however, for example, due to a clot, so that the vacuum effect weakens and accordingly the wound insert needs to be changed.
From U.S. Pat. No. 4,382,441 it is known that a wound insert made of small-porous foam or a textile material is placed on the wound surface and is closed off with a cover that covers the wound and is fastened around the wound surface. Hoses, which serve as supply and drain hoses, lead into the wound insert. A liquid treatment may be piped into the wound insert through these hoses, so that the treatment may come in contact with the wound surface. No vacuum is thereby produced in the wound insert. The problem of clogging may also appear in this situation.
According to EP 0 880 953 B1 the wound treatment device is improved in such a way that the supply hose and the vacuum hose may be controlled independently of one another, so that the supplied liquid treatment may be absorbed into the wound over an adjustable time period, while time intervals can be alternated where no liquid treatment is absorbed by the wound and if necessary a pressure is produced. This type of vacuum produces a pull-effect on the wound's tissue cells, thereby promoting cell growth and tissue proliferation.