VAC Therapy

Vacuum assisted closure has been around for a while now, and I have certainly witnessed its ability to close a gnarly wound. It really does appear to work better than the old fashioned wet-to-dry dressings. But I've wondered what really goes into the wound healing process using this system. I've learned that the negative pressure dressing applies forces inducing macrostrain and microstrain.

Macrostrain you see immediately when the suction is turned on and the wound edges are brought closer together. The suction pulls off infectious materials and edema. The pressure of the sponge against the wound bed also induces microstrain, essentially stretching of cells. The cells respond to this stain by expressing different receptors on the cell surface that ultimately promote healing. Through this there is an increase in cell proliferation, extracellular matrix production, wound perfusion, and the subsequent formation of granulation tissue.

For those that haven't worked with VAC therapy, you place foam directly on the wound bed and cover with a transparent plastic adherent. Then you have to snip a few holes in the plastic where you will attach the suction tubing. The fluids are pulled from the wound, through the sponge, and travel through the tubing into a canister. Above is a picture a VAC sponge, applied to presumably a sacral decub, with suction turned on. The little ring in the middle the black sponge is part of the tubing- this ring/circle is what you place over the holes you made. You can also see the plastic around the sponge on normal skin. When VACs are removed, you see the characteristic little bumps or ridges formed by the sponge in [hopefully] healthy tissue.