Tissue oxygenation and negative-pressure wound therapy when applied to the feet of persons with diabetes mellitus: An observational study

PURPOSE: Our group has reported that negative-pressure wound therapy (NPWT) decreases tissue oxygenation by 84% in the foot of diabetic patients because the pad of the connecting drainage tube and foam sponge of the NPWT system compress the wound bed. The purpose of this study was to determine whether an NPWT modified dressing application reduces tissue oxygenation in the feet of persons with diabetes mellitus. DESIGN: A prospective, clinical, observational study. SUBJECTS AND SETTING: We enrolled 30 patients with diabetic mellitus; their mean age was 63.9 ± 11.2 years (mean ± standard deviation). All were cared for at the diabetic wound center at an academic tertiary medical center in South Korea between 2014 and January 2015. METHODS: Transcutaneous partial oxygen pressures (TcpO²) were measured to determine tissue oxygenation levels beneath modified NPWT dressings. A TcpO₂ sensor was fixed at the tarsometatarsal area of the contralateral unwounded foot. A negative pressure of-125 mm Hg was applied until TcpO₂ reached a plateau state; values were measured before, during, and after the modified NPWT. The Wilcoxon' and Mann-Whitney U tests were used to compare differences between these measurements. RESULTS: TcpO₂ levels decreased by 26% during the modified NPWT. Mean TcpO₂ values before, during, and after turning off the therapy were 54.3 ± 15.3 mm Hg, 41.6 ± 16.3 mm Hg, and 53.3 ± 15.6 mm Hg (P <.05), respectively. CONCLUSION: Applying NPWT without the pad of the connecting drainage tube significantly reduces the amount of tissue oxygenation loss beneath foam dressings on the skin of the foot dorsum in diabetic patients.