Tissue Pressure Changes and Implications on Dressing Selection when utilising Negative Pressure Wound Therapy on an Ex Vivo Porcine Model

Negative Pressure Wound Therapy (NPWT) is broadly used in surgical wound management and more recently burn care; however, the tissue pressure changes and best dressing application technique remains unknown. This study was done to help understand the tissue pressure changes beneath negative pressure when varying the delivered pressures, dressing thickness and distribution of dressings. This study was done in 2021 at a quaternary paediatric burns hospital. Utilising a cadaveric porcine model, an intracranial pressure monitor and transducer were used to assess pressure. The transducer was placed on the epidermis or inserted under ultrasound guidance via cannulation to the dermis, subcutaneous or muscular layer. Mepitel (TM), ACTICOAT (TM), varying layers of Kerlix (TM) (10, 20 or 30 layers) and NPWT were then applied either circumferentially or non-circumferentially. Each set of results is indicative of the intracranial pressure probe reading when NPWT was delivered at -40, -60, -80, -100 and -120 mmHg. The median and interquartile pressure recordings were epidermis: -42 (-42.5 - -41), -60.5 (-62.5 - -60), -80.5 (-82 - -80), - 99 (-99 - -98)mmHg (p < 0.001); dermis: 1 (0 - 2), 2 (1 - 3.5), 3 (2 - 5.5), 4 (3 - 7), 5.5 (4 - 7.5)mmHg (p < 0.001) (the increase in pressure was less when circumferential dressings (p < 0.001) or more layers of Kerlix were applied (p < 0.001)); subcutis: 1.5 (-4.5-1), -2.5 (-7.5 - 1.5), -3.5 (-11 - 1.5), -5 (-14 - 1.5) and -6 (-16 - 2)mmHg (p = 006) (the decrease in pressure was less with increased layers of Kerlix (0.047) and muscular: 0 (-0.5 - 0), 0 (-1 - 0.5), 0 (-1 - 1), 0 0 (-1 - 1), 00 (-1.5 - 1)mmHg (p = 0.55). These data suggest negative pressure paradoxically exerts a positive pressure on the dermis. Circumferential and multi-layer dressings reduce this positive pressure. This knowledge has impacted our burn negative pressure wound therapy dressing selection. The limitation of this study is the cadaveric model, a live model is suggested for future studies.