**4.3 Pressure ulcers**

These kinds of ulcers are common in patients who have compromised sensory perception and mobility, are either paralyzed or unconscious, and cannot respond to the periodic need for repositioning. When the capillary pressure is exceeded by tissue compression due to prolonged, unrelieved pressure or shear leads to ischemia necrosis. This is the result of tissue hypoxia and ischemia-reperfusion injury. Usually, skin over bony prominences, such as the sacrum, hips, and malleoli, is vulnerable to pressure ulcers. This may be caused after as little as two hours of immobility [18]. **Figure 12** shows the four different stages of pressure ulcers.
