Notes on the pathogenesis of serious pressure sores

It is often assumed that pressure sores are caused by the flattening of blood capillaries, resulting in tissue ischaemia. However, the available evidence, especially that from animal experiments, indicates that microvascular trauma has a significant part to play. Published curves showing the relationship between level of pressure and duration of application also show that simple ischaemia is an inadequate explanation of pressure sore pathogenesis. The crucial pressure (tissue pressure) is normally estimated from interface pressure measurements. However, the relationship between tissue pressure and interface pressure is more complex than is generally realized. Other factors, such as shearing and static friction, are discussed briefly, and recommendations are made for clinical practice and further research.