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Pressure Ulcers: A Review of Pathophysiology, Risk Factors, and Management Principles

Chris Overgaard, MD, MSc

Introduction
Pressure ulcers are common in elderly patients who suffer from an acute illness causing immobility, and for those patients with chronic disabilities who are confined to a bed at home, or in a chronic care facility.1 The development of these ulcers represents a major medical problem that can, by itself, necessitate admission to hospital, or significantly prolong the length of stay in a hospital in patients who were admitted with other illnesses. In this brief review, the scope of the medical problem associated with pressure ulcers is examined, etiology and risk factors are discussed, and preventative measures and treatment options, based on recently published consensus guidelines, are summarized.

Terminology
Descriptions of pressure ulcers exist from as early as 3000 B.C, but the bulk of the literature on this problem has been published since World War II, when this complication developed in immobilized casualty victims.1 Original terminology used the expression 'bedsores' to describe ulcer formation; common medical terminology for this problem include decubitus ulcers, decubiti, and pressure sores. The word 'decubitus' is a Latin expression referring to a lying position which was first coined by French physicians and nurses in the 1700's. 'Pressure ulcer' is now the preferred medical term, since it hints at the central pathophysiological process behind ulcer formation.

Scope of the problem
The prevalence of pressure ulcers in acute care facilities has been estimated in the literature as being between four and thirty percent.2-4 The incidence of new ulcer formation in elderly patients has been estimated at 66% for patients hospitalized with femoral fractures and 33% for critical care patients.3 Although numbers vary widely in the literature, health care costs required to heal a single ulcer have been estimated between $5,000 and $60,000 per ulcer.3,6

Pressure ulcers place an intense strain on hospital resources including nursing care required to change dressings, physical therapy, medications, nutritional support, and physician services.4 They have also been shown to increase the risk of mortality among geriatric patients and nursing home residents by four-fold. Pressure ulcers increase the patient's length of stay, the time required for recuperation, and increase the risk of developing complications, such as sepsis.4 The development of pressure ulcers has been identified as a marker for the severity of an underlying disease and the presence of comorbidities.6

Definition and Classification
A pressure ulcer is defined as an area of local tissue necrosis which usually develops when soft tissues are compressed, for prolonged periods of time, between bony prominences and any external surface.2 In general terms, they result from mechanical injury to the skin and tissues which causes hypoxia and ischemia, leading to cell death. Patients with ulcers often present with pain, although they can be an incidental finding on examination of an infirmed patient who is unable to communicate.

Clinical consensus guidelines on pressure ulcers were published in 1994 by the U.S. Department of Health and Human Services in collaboration with the Agency for Health Care Policy and Research (AHCPR).5 Please see table 1 for the recommended classification scheme for ulcers.

Pathophysiology and Risk Factors
Figure 1 is a basic schematic illustrating the pathophysiological process involved in the formation of ulcers.3,4 In brief, prolonged pressure on tissue leads to microvascular vessel occlusion and the development of tissue hypoxia. This leads to localized tissue ischemia, resulting in the development of inflammation, increased vascular permeability, and protein accumulation in the local interstitium. The result is increased tissue edema and the worsening of perfusion. This vicious cycle ultimately results in the development of a pressure ulcer.

Major physical factors leading to formation of ulcers are pressure (intensity, duration, tissue