Negative-pressure wound therapy I: the paradox of negative-pressure wound therapy.

BACKGROUND: Does negative-pressure wound therapy reduce or increase the pressure of wound tissues? This seemingly obvious question has never been addressed by a study on living tissues. The aim of this study was to evaluate the nature of tissue pressure changes in relation to negative-pressure wound therapy.
METHODS: Three negative-pressure wound therapy dressing configurations were evaluated-circumferential, noncircumferential, and those within a cavity-on 15 human wounds, with five wounds in each category. Tissue pressure changes were recorded (using a strain gauge sensor) for each 75-mmHg increment in suction, up to -450 mmHg. In the circumferential and noncircumferential groups, tissue pressure was also measured over a 48-hour period at a set suction pressure of -125 mmHg (n = 10).
RESULTS: In all three groups, mean tissue pressure increased proportionately to the amount of suction applied (p < 0.0005). Mean tissue pressure increments resulting from the circumferential dressings were significantly higher than those resulting from the noncircumferential (p < 0.0005) or cavity group (p < 0.0005); however, there was no significant difference between the latter two groups (p = 0.269). Over the 48-hour period, there was a significant mean reduction in the (increased) tissue pressure (p < 0.04 for circumferential and p < 0.0005 for noncircumferential), but in only three of 10 cases did this reduce to pressures less than those before dressing application.
CONCLUSIONS: Negative-pressure wound therapy increases tissue pressure proportionately to the amount of suction, although this becomes less pronounced over 48 hours. This suggests that negative-pressure wound therapy dressings should be used with caution on tissues with compromised perfusion, particularly when they are circumferential.