Positive pressure of negative pressure wound therapy

Dr Douglas Copson1,2, Prof Fiona Wood1, Mr Jeremy Rawlins1,2

1Fiona Stanley Hospital, 2Royal Perth Hospital


Negative wound pressure therapy is being applied in an ever increasing range of clinical situations. The use of NWPT on closed incisions has gained popularity recently as well as the use of NWPT in burns patients to apply compression over split skin grafts while providing an effective method of exudate control.

Methods / Design

We undertook a study looking into the macroscopic positive pressure VAC dressings apply over closed uninjured skin. Pressures were tested on a healthy volunteer over the anterolateral thigh to record real world pressures. Pressures were also tested on a solid surface to record the relationship of set negative pressure to maximum macroscopic positive pressure applied to a closed wound.


We found that when NWPT was applied over uninjured skin the positive pressure applied to the wound was constant across a wide range of negative suction settings. The surface pressure increased when NWPT was applied over wound beds with increased densities.

When tested NWPT on a solid surface to record maximum positive pressure NWPT could deliver over a closed incision there was a linear relationship ranging from 11mmHg positive pressure at a setting of -25mmHg to 40mmHg at a setting of -200mmHg.


This study provides further data in understanding the mechanism of negative wound pressure therapy. Understanding the pressure applied via NWPT can guide clinical application over pressure sensitive structures such as free flaps and also rigid structures such as periosteum/bone.

Key Words

Negative Wound Pressure Therapy

Dr Douglas Copson is a Plastic and Reconstructive Surgery registrar training in Perth, Western Australia.

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