A Randomised Cross-Over Study to Evaluate the Physiological Effects of Internal Air Pressure Changes in Advanced Support Surface Design.

High specification mattresses periodically redistribute pressure using alternating air cells, offloading tissues. This study aimed to evaluate the effects of alternating air pressure gradients on sacral tissue physiology. This randomised cross-over study recruited 15 healthy participants to test the three mattress settings (fast cycle, normal cycle, and slow cycle). Participants were asked to adopt supine, lateral, and high sitting (head of bed at 40°) postures, whilst transcutaneous tissue gas tensions and interface pressures at the sacrum were continuously monitored. Comparison between mattress settings and postures showed no statistical difference (p > 0.05) between peak pressure index values at the sacrum for each air inflation cycle speed setting. By contrast, a significantly higher sacral (p < 0.05) contact area was observed for high sitting. During high sitting, ischemic responses during both fast and normal air inflation cycle speed settings were recorded. During the slow air inflation cycle speed, most participants (60%-100%) showed high levels of perfusion. The present study identified a main effect of posture on interface pressure and perfusion over the sacrum. The alternating mattress speed influenced local tissue perfusion, with the greatest changes in tissue oxygenation occurring in a high-speed setting.