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What causes pressure sores?
A fit and well person will move position subconsciously as an area of soft tissue is being deprived of blood and nourishment. If, due to spinal cord injury, old age, very young age, a long-term illness, a sudden event or condition such as being unconscious or during an operation, a person is unable to make these small movements a pressure sore may result. Pressure sores can occur in people of any age who are bedridden, chairbound, or unable to reposition themselves. However, they frequently affect older people. Also pressure sores occur in patients with diminished sensation or who are emaciated. Some conditions (for example diabetes, stroke) and some treatments (eg epidural pain relief) may reduce the sensitivity to pain or discomfort so that people are not aware they need to move.
Pressure occurs when skin and tissue is directly compressed between bone and a surface, such as a bed or chair. The degree of pressure sore depends on the intensity and duration of the pressure. Low pressure causes tissue damage if sustained over several hours whereas high pressure causes tissue damage within minutes.
Shear occurs when tissues are wrenched in opposite directions, for example when sliding down in a bed. Shearing forces are the cause of many sacral ulcers. When the head is elevated, the skeletal frame slides toward the foot of the bed causing friction with the bed linen. This abrasion exposes the skin to bacterial invasion and infection. It is most common in individuals who spend long periods in semi-recumbent positions e.g. slowly slipping down in a bed or chair.
Friction can be caused by rubbing against a sheet. Sores are superficial but are still painful, making the skin more prone to further skin damage. Repeated irritation may wear away the top layers of skin. Such irritation may occur if a person scrapes the heels, elbows, or knees or wears poorly fitted shoes. Also this can occur due to poor lifting and moving techniques.
Moisture makes skin tissue more vulnerable to breakdown. Prolonged exposure to moisture (often perspiration, urine, or faeces) weakens and damages the skin surface, making pressure sores more likely.
Inadequate nutrition increases the risk of developing pressure sores and slows the healing process of sores that do develop. Malnourished people lack the protective layer of fat that helps pad the skin and that keeps the blood vessels from being squeezed shut. People whose diets are deficient in protein, vitamin C, or zinc, which are essential for normal skin repair, are at increased risk as well.
Poor circulation caused, for example, by vascular disease or heavy smoking, may increase the risk of pressure ulcers.
