The damage is caused when underlying muscle fibres and subcutaneous tissues are ripped and separated. When this occurs there is a release of clotting factors within the tissue and blood clots occur which block the microcirculation. TOP Friction Friction is the resistance to movement between two surfaces when subjected to forces parallel to the two surfaces. When this occurs between two surfaces shear forces are produced within those two surfaces. Therefore the greater the friction between two surfaces the greater the shear force component is within the two surfaces.
Friction occurs between the patient and the support surface.
Friction is increased by moisture and temperature which change the characteristics of the support surface. This is an important consideration if the patient is incontinent or has a raised body temperature. It is more common in areas where the papillary layer, which anchors the dermis, such as in the back. Friction ulcers often occur when the patient repeatedly slips down the bed, especially with the use of back rests or when the bed is elevated. TOP Intrinsic factors Any systematic condition that compromises the peripheral vascular circulation, eg. renal failure, congestive cardiac failure, diabetes.