Pressure ulcers develop at body-support interfaces over bony prominences as a result of external compression of the skin, shear forces, and friction, which produce ischemic tissue necrosis. Pressure ulcers occur in patients who are obtunded mentally or have diminished sensation (as in spinal cord disease) in the affected region. Secondary infection results in localized cellulitis, which can extend locally into bone or muscle or into the bloodstream with resultant bacteremia and sepsis.
External compression of the dermis and hypodermis leads to ischemic tissue damage and necrosis. Risk factors for developing pressure ulcers: inadequate nursing care, diminished sensation/immobility (obtunded mental status, spinal cord disease), hypotension, fecal or urinary incontinence, presence of fracture, hypoalbuminemia, and poor nutritional status. The mean skin capillary pressure is approximately 25 mmHg. External compression with pressures <30 mmHg occludes the blood vessels so that the surrounding tissues become anoxic. Amount of damage is proportional to extent and duration of pressure. Healthy individuals can tolerate higher pressures. Repositioning the patient every 1 or 2 h prevents the interface skin over a bony prominence from becoming ischemic, with subsequent ulcer formation. Secondary bacterial infection can enlarge the ulcer rapidly, extend to underlying structures (as in osteomyelitis), and invade the bloodstream, with bacteremia and septicemia. Infection also impairs or prevents healing.
A pressure sore may initially appear as a red area of skin that does not disappear after a few hours and it may feel tender. The area may become painful and purple in colour. Continued pressure and poor circulation cause the skin and tissue to break down.
An open sore may develop when an area of tissue dies. The sore may then become infected. In severe cases the sore increases in size and may cause destruction to muscle and bone underneath the skin.
Pressure sores are most common on the heels and on the hips. Other areas at risk for pressure sores include the base of the spine, the shoulder blades, the backs and sides of the knees, and the back of the head.
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