Measurement of interface pressures in the evaluation of operating theatre mattresses

This study compared the sacral interface pressures obtained in four mattresses (all supplied by the same manufacturer), in two positions adopted for surgical procedures, to determine the similarities and differences between them. The mattresses were all variations of the standard product used in operating departments. The null hypotheses were that there are no differences in interface pressures between the mattresses or between the two surgical positions, and that measurements are not influenced by subject body mass index. The measurement technology was also tested for reliability and suitability for intra-operative use. Sacral interface pressures of 25 healthy volunteers were recorded using each of the four mattresses (order individually randomised) in both the supine and the Lloyd Davies positions. A pressure-sensitive mat was used and one-way analysis of variance was the main statistical approach. Statistical significance was determined by p-values of < or = 0.05. One mattress recorded significantly lower interface pressures than the others and all pressures were influenced by body mass index. Surgical position was a significant factor, measurements in the Lloyd Davies position being 9.5-14.2% higher than in the supine position. The pressure measurement technique has proved to be reliable and easy to calibrate, position and use. Indications are that it can be used safely and effectively in operating departments. These results have implications for researchers and clinicians.