Figure 1.

Schematic illustration of the different modes of applying negative pressure. (a) In continuous negative pressure wound therapy (NPWT), the pressure is kept constant, for example, at -80 mm Hg. (b) In intermittent pressure therapy (IPT), the negative pressure is repeatedly switched on and off (for example, alternating between 0 and -80 mm Hg). (c) In variable pressure therapy (VPT), the pressure is varied smoothly between 2 levels (for example, -10 and -80 mm Hg), thus maintaining a negative pressure environment throughout the therapy.