Ischial Pressure Distribution Under the Seated Person

One area in which technology may assist in the prevention of pressure sores is in the monitoring of physical conditions at the interface between the body tissues and a support surface. This is particularly relevant in the immobile and debilitated subject, who is especially prone to tissue breakdown. The extrinsic factors generally considered to be of importance in the assessment of tissue viability include normal pressure, shear stress, temperature, movement and moisture levels. This has led to the development of several non-invasive systems which measure accurately the pressure distribution at the patient-support interface (Garber et al., 1978; Bader et al., 1985). Clearly, tissue ischaemia will result if localised interstitial stresses reach values in excess of the capillary pressure, reported as 32 mmHg (4.3 kPa) by Landis (1930). However, as a result of the intervening soft-tissue layer, the level of tolerable pressure at the tissue interface will be generally higher, although its absolute value will depend upon the many intrinsic factors specific to an individual.