Schematic diagram of NPWT systems with commonly available component options. A wide variety of NPWT systems are available to clinicians today. The interface material is typically an open pore polymeric foam, but some systems use gauze. This material is covered with a semi-occlusive dressing that forms a seal over the wound. Connecting tubing goes to a pump that can apply continuous, intermittent, or periodic vacuum pressure, usually ranging from 50 to 150 mmHg. Wound exudate is collected in a cannister, which frequently is filled with a desiccant or gelation agent. Some systems also have the capacity for wound irrigation.