Effect of Alternating Pressure Overlay on Skin Blood Flow and Interface Pressure in Spinal Cord Injury

Pressure injuries are serious complications that are difficult and expensive to treat. Preventative strategies, such as alternating pressure mattress has been prescribed to patients with pressure injury in the hospital setting to prevent recurrence. However, the underlying mechanism of alternating pressure (AP) on tissue tolerance to ischemia is not explored to a full extent. The main purpose of this study was to investigate the protective mechanism of alternating pressure overlay on load-bearing tissue like sacrum in people with spinal cord injury (SCI). We hypothesized that the low-profile AP overlay would redistribute the interface pressure and subsequently increase the skin blood flow (SBF) to the sacral area when lying on top of an operating room (OR) pad. A secondary aim was to investigate if AP overlay could be used as a preconditioning strategy for weight-bearing skin at the sacrum. We hypothesize that after preconditioning with AP overlay, the interface pressure would remain unchanged during supine lying on OR, but SBF would increase. A repeated measures design was utilized on 15 adults with SCI. All the individuals underwent three protocols: supine lying on (1) OR pad only for 40 minutes (control), (2) OR pad with AP overlay for 40 minutes, and (3) OR pad only (AP-OR) for 40 minutes after AP (protocol 2). Outcome measures included interface pressure and SBF at sacrum. For the primary aim, we found that the peak interface pressure during AP-deflation (51.47±30.18 AU) was significantly lower than that during AP-inflation (89.27±53.92 AU) and OR (control protocol) (114.13±60.97 AU). The averaged SBF during AP-deflation (15.54±15.33 AU) was significantly higher than that during inflation (12.65±12.45 AU) and OR (control) (11.96±10.26 AU). For secondary aim, we found that peak interface pressure during AP-OR (104.62±58.17 AU) was significantly lower than that during OR (control) protocol (114.13±60.97 AU), and SBF during AP-OR (15.78±15.82 AU) was significantly higher than that during OR (control) (11.96±10.26 AU). Findings of this study suggested that alternating pressure overlay is an effective strategy to redistribute interface pressure and subsequently improves tissue perfusion at the weight-bearing area in people prone to pressure injury. Further study is warranted in other population at risk of pressure injuries