The etiology of pressure ulceration is multifactorial. Blood pressure at the arterial end of the capillary loop is approximately 30 mm of mercury. Since pressures over bony prominences have been measured at between 40-150 mm of mercury, it seems clear that ischemic necrosis is the probable pathologic event. The length of time necessary for ischemia to produce ulceration varies with each person and situation, but is not long in any case. Generally, it is believed that two hours of pressure-induced ischemia is sufficient to begin the process of skin ulceration.
Most pressure ulcers begin as a red area of skin.
Given the magnitude of the problems that arise when such areas are allowed to progress to ulceration, this early stage should be considered a medical emergency. The pressure on the area should be relieved quickly and should not be re-applied until the skin has recovered, even if this requires hospitalization. A hospital stay of a few days, to heal this type of pressure problem, is preferable to the longer stay required after the skin and underlying tissues are actually destroyed. Without proper care, the early stage proceeds to actual ulceration. If this ulceration involves only a small area of skin or a partial thickness skin loss, the sore may still be treated nonsurgically.