The Effectiveness of Negative Pressure Wound Therapy in Inducing Hypoxia Compared to Standard Occlusive Dressing Wound Therapy in the Healing of Traumatic Wounds

Abstract

Background: Negative Pressure Wound Therapy has gained popularity as an effective adjunct in management of wounds. It accelerates wound healing by enhancing granulation tissue formation. Its mechanism of action was always postulated to increased perfusion and oxygenation to the wound. However, recent postulates seem to suggest that it reduces perfusion to the wound thus creating a hypoxic environment which stimulates vascularization and angiogenesis. Objective: To establish the effectiveness of Negative Pressure Wound Therapy in inducing hypoxia compared to Standard Occlusive Dressing Wound Therapy in the healing of traumatic wounds. Study Design: This was a randomized C;;;ontrolled trial Settings: The study was undertaken at the Kenyatta National Teaching and Referral Hospital from the months of October 2020 to April 2021 Materials and Methods: The study participants were patients with traumatic wounds admitted in the surgical wards at the Kenyatta National Teaching and Referral Hospital and were divided into two groups where one group was subjected to Negative Pressure Wound Therapy and the other group subjected to Standard Occlusive Dressing Wound Therapy. The samples for analysis were obtained though punch biopsies of wounds at two sites; the wound edges and the wound bases and they were carried out at baseline day 0, day 3 and day 7 in each group. They were homogenized and stored at -800C until enough samples accumulated for analysis in a 96-well ELISA plate. ELISA assays for quantitative levels of Hypoxia Inducible Factor 1 alpha and Fibroblast Activation Protein was carried out to obtain optical densities which were converted to actual concentrations of the two elements through Standard Absorbance Curves. Results: The concentration of Hypoxia inducible factor 1 alpha, both at the wound edges and wound bases, increased by 176% and 194% respectively from baseline to day 7 of therapy in wounds managed by Negative Pressure Wound Therapy. A slight concentration increase of 23% and 21% (respectively) was noted in wounds subjected to Standard Occlusive Dressing Wound Therapy. Similarly, the concentration of Fibroblast Activation Protein increased both at the wound edges and wound bases by 124% and 146% respectively from baseline to day 7 of therapy in wounds treated by Negative Pressure Wound Therapy. A slight increase by 37% in wounds subjected to Standard Occlusive Dressing Wound Therapy was noted at both the wound edges and wound bases. Discussion: Our findings are additive to initial studies that demonstrated reduced blood flow and reduced transcutaneous partial pressure of oxygen in wounds subjected to Negative Pressure Wound Therapy. Our study further demonstrates the molecular mechanisms that result from the hypoxia induced in wounds managed by Negative Pressure Wound Therapy and the molecules generated enhance granulation tissue formation. Conclusion: Hypoxia induction should be recognized as a mechanism of action through which Negative Pressure Wound Therapy through increases wound healing by enhancing granulation tissue formation.