Q: Negative pressure wound therapy (NPWT), popularly known as (wound-VAC) increase blood flow due to subatmospheric pressure. At what level of negative pressure it may have reverse effect?


Answer: -175 mm Hg

In NPWT a  portable pump is connected to apply negative suction pressure of -50 to -175 mmHg. This increase the blood flow and helps in healing. Above - 175 mmHg there may be an adverse effect of decreased blood flow.


Reference:


Kairinos N, Voogd AM, Botha PH, et al. Negative-pressure wound therapy II: negative-pressure wound therapy and increased perfusion. Just an illusion? Plast Reconstr Surg 2009; 123:601.