Study of main and cross-over effects on pressure relief among body mass index (BMI), body position and supporting material properties.

Pressure ulcers influence people with limited mobility who must spend a long time lying or sitting because these positions create high interfacial pressure between the body and supporting materials. Supporting materials, such as mattresses and cushions, are designed to prevent pressure ulcers by increasing the contact area, reducing the interfacial pressure or reducing the contact time. Foam is the most common supporting material for relieving pressure because it is cheap and easy to change its shape to fit the contour of the body. Past studies showed that BMI, body position and supporting material properties have an impact on relieving pressure; however, there is no study of the main and cross-over effects among these parameters. This study aims to investigate the main and cross-over effects among BMI, body position and supporting material properties on pressure relieving performance using univariate ANOVA and correlation analysis. It was found that body position and foam density were the main effect and BMI and body position, and body position and foam density were the cross-over effects on pressure relief. It was also found that low density Polyurethane (PU) foam of less than 4 cm in thickness as well as the appropriate K2 and K3 moduli are best suited for pressure relief. The actual value of foam thickness and the appropriate K2 and K3 moduli are subject to BMI values and body position. The significance of the outcomes from this study is that it will aid in optimizing the design of supporting materials with varied BMI values and body positions to greatly reduce pressure ulcers for ailing patients.