A gauze or foam dressing containing a drainage tube is applied to a deep or irregularly shaped chronic or surgical wound and is sealed with transparent film. The tube is connected to a pump that applies sub-atmospheric pressure to the wound bed, removing fluid, allowing blood vessels to dilate and enhancing granulation of wound tissue. The vacuum may be applied continuously or intermittently, depending on the type of wound being treated and the clinical objectives. Intermittent removal of wound exudates supports the cleaning and drainage of the wound bed and the removal of infectious material. NPWT has two forms that mainly differ in the type of dressing used for transferring NPWT to the wound surface: gauze or foam. Gauze is referred to as the Chariker-Jeter technique and involves a drain wrapped in gauze topped by a sealed transparent dressing. Foam uses a sealed polyurethane foam dressing attached by a tube to a vacuum pump.
The technique is usually performed on chronic wounds, or wounds that are expected to present difficulties while healing (such as those associated with diabetes or when the veins and arteries are unable to provide or remove blood adequately). In addition to treating chronic wounds, NPWT has been employed as a technique to bridge large cavities temporarily in open surgeries, including reconstructive, gastrointestinal and general surgery. For example, NPWT reduces the incidence of abdominal compartment syndrome while prolonging time of temporary closure before fascial closure.