A pressure ulcer is an area of localized cellular damage to the skin and underlying tissues, usually over a bony prominence, caused by unrelieved and prolonged pressure, shearing and friction or a combination of these forces.
Generally, pressure ulcers occur when a person is in a sitting or lying position for too long without shifting their weight. Blood vessels supply oxygen and nutrients to every part of the body, including the skin. Constant pressure in one area means that blood and nutrients are less able to reach the skin in this area. Tissue is deprived of oxygen and other nutrients, and if left untreated, the affected tissue eventually dies.
Although unrelieved pressure is the main cause of pressure ulcers, a combination of other factors such as friction (from rubbing, dragging) and shear (sliding down the bed) can also contribute to skin damage leading to a pressure ulcer.
Poor lifting and moving techniques can remove the top layers of skin due to friction with bed or chair surfaces. Repeated friction can increase the risk of pressure ulcers. Sliding forces ‘shears’ the upper layers of skin away from the deeper layers. This can happen when you slide down, or are dragged up in a bed or chair.