Pressure-Relieving Systems and Surgery

The aetiology of pressure sores is a combination of factors that add to a locally critical ischemia in the soft tissues. Loss of mobility or impaired protective sensation or a combination of both are preconditions for such tissue damage. An interface pressure significantly exceeding the average capillary pressure (2.7 to 6.3 kPa) for more than 2 h will normally result in tissue necrosis [9]. It has been demonstrated that the transcutaneous measurement of oxygen pressure (pO2) in healthy adults decreases rapidly to zero when the subjects are lying motionless on a normal hospital mattress [8]. Many minor factors such as centralisation of blood flow (for instance in shock) or hyperaemia (fever), reduced general condition, especially nutritional deficit, cardiac insufficiency, medications like steroids or catecholamines, prominent pointed bones (ischial or trochanter tuberosities) in rather slim patients and, last but not least, the quality of the mattress or cushion underneath the subject play a role as well.