Potential for bed sores due to high pressures: influence of body sites, body position, and mattress design.

Pressures were measured on 10 subjects, supine and sitting, under six anatomical sites prone to bed sores on three different mattresses. Studied were the Clinifloat and Therarest specialist replacement mattresses, and a standard hospital mattress. Mean supine pressures were less than 5 kPa under four sites. Average supine buttock pressure was 2.93 kPa. Occiput and heel pressures were much higher than under other sites, being on average 2.6 and 4.5 times greater respectively than the mean buttock pressure. On sitting up, buttock pressure increased by a factor of 1.7 on average, to a level higher than the accepted capillary closing pressure. Measurements were consistent with mattress design, specific features of which can significantly affect pressure under certain sites.