There are four mechanisms that contribute to<unk>  development: # External (interface)<unk>  applied over an area of the body, especially over the bony prominences can result in obstruction of the blood capillaries, which deprives tissues of oxygen and nutrients, causing ischemia (deficiency of blood in a particular area), hypoxia (inadequate amount of oxygen available to the cells), edema, inflammation, and, finally, necrosis and ulcer formation. Ulcers due to external<unk>  occur over the sacrum and coccyx, followed by the trochanter and the calcaneus (heel). # Friction is damaging to the superficial blood vessels directly under the skin. It occurs when two surfaces rub against each other. The skin over the elbows can be injured due to friction. The back can also be injured when patients are<unk> lled or slid over bed sheets while being moved up in bed or transferred onto a stretcher. # Shearing is a separation of the skin from underlying tissues. When a patient is partially sitting up in bed, their skin may stick to the sheet, making them susceptible to shearing in case underlying tissues move downward with the body toward the foot of the bed. This may also be possible on a patient who slides down while sitting in a chair. # Moisture is also a common<unk>  culprit. Sweat, urine, feces, or excessive wound drainage can further exacerbate the damage done by<unk> , friction, and shear. It can contribute to maceration of surrounding skin thus potentially expanding the deleterious effects of<unk> s. Risk factors There are over 100 risk factors for<unk> s. Factors that may place a patient at risk include immobility, diabetes mellitus, peripheral vascular disease, malnutrition, cerebral vascular accident and hypotension. Other factors are age of 70 years and older, current smoking history, dry skin, low body mass index, urinary and fecal incontinence, physical restraints, malignancy, and history of<unk> s.
Pressure ulcer
Venous ulcer
Arterial insufficiency ulcer
Hair loss
Linguatulosis
Gangrene
Diabetic foot ulcer
Veinoplus