Wound edge microvascular blood flow during negative-pressure wound therapy: examining the effects of pressures from -10 to -175 mmHg.

BACKGROUND: Negative-pressure wound therapy is believed to accelerate wound healing by altered wound edge microvascular blood flow. The current standard negative pressure is -125 mmHg. However, this pressure may cause pain and ischemia and often has to be reduced. The aim of the present study was to examine the blood flow effects of different levels of negative pressures (-10 to -175 mmHg). METHODS: Wound edge microvascular blood flow was studied in a peripheral wound model in eight 70-kg pigs on application of negative-pressure wound therapy. Blood flow was examined, using laser Doppler velocimetry, in subcutaneous and muscle tissue at 0.5, 2.5, and 5 cm from the wound edge. RESULTS: Blood flow changed gradually with increasing negative pressure until reaching a steady state. Blood flow decreased close to the wound edge (0.5 cm) and increased farther from the wound edge (2.5 cm). At 0.5 cm, blood flow decreased 15 percent at -10 mmHg, 64 percent at -45 mmHg, and 97 percent at -80 mmHg. At 2.5 cm, blood flow increased 6 percent at -10 mmHg, 32 percent at -45 mmHg, and 90 percent at -80 mmHg. Higher levels of negative pressure did not have additional blood flow effects (p > 0.30). No blood flow effects were seen 5 cm from the wound edge. CONCLUSIONS: Blood flow changes gradually when the negative pressure is increased. The levels of pressure for negative-pressure wound therapy may be tailored depending on the wound type and tissue composition, and this study implies that -80 mmHg has similar blood flow effects as the clinical standard, -125 mmHg.