Determining the optimal inner air cell pressure for the effective reduction of interface pressure.

Alternating-pressure air mattresses can reduce interface pressure and prevent pressure ulcer development. However, bottoming out sometimes occurs, resulting in an increase in interface pressure. Therefore, optimal settings should be determined based on interface pressures and inner air cell pressures. The purpose of this study was to investigate the most effective inner air cell pressure to reduce interface pressure without causing bottoming out. A new alternating air mattress was used, which comprised three layers: a base layer, fitting (F) layer, and alternating layer. The alternating layer comprises inflated (I) cells and deflating (D) cells. The study participants were 13 healthy volunteers over 18 years of age, each of whom adopted supine position on the mattress. The pressures in the D cells were gradually deflated under different I cell and F layer pressure settings. We measured peak sacral pressure and inner air cell pressure to obtain the bottoming out cut-off values by using receiver-operating-characteristic (ROC) curves. We then investigated the effectiveness of different settings to reduce the peak sacral pressures. A number of test conditions were evaluated. Results indicated that the D cell pressure cut-off points were 1.26 kPa and 1.21 kPa, for phases 1 (F = 4 kPa, I = 4 kPa) and 4 (F = 1 kPa, I = 4 kPa), respectively. These settings significantly reduced the interface pressure (P < 0.001, P = 0.026, respectively). Our results suggest that appropriate configuration of inner air cell pressure could reduce interface pressure without causing bottoming out.