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INTRODUCTION
One of the common manifestations of chronic disease and disability is the abnormal loading of skin and other surface tissues unaccustomed to bearing large mechanical forces. There are many general etiologies, including paralysis, altered sensation, altered level of consciousness, prolonged bedrest and sitting, and the use of an orthosis or prosthesis.
A result of abnormal mechanical loading of surface tissues is breakdown. Though breakdown might appear initially as only a slight reddening of the skin, it can develop into a significant injury that damages tissues through the entire thickness of the body wall. Changes in color of the skin, blisters, bruises, and excoriations often develop and are signs of early breakdown. If loading continues unchanged in an area that demonstrates early breakdown, irreversible injury and necrosis might occur. More extensive pressure ulcers develop which extend deeper into subcutaneous tissues, sometimes into joint or body cavities. Typically, these more extensive ulcers require debridement of necrotic tissues followed by prolonged periods of pressure relief. Both conservative and surgical treatment programs are then employed to debride the pressure ulcer and allow healing of tissues.
The principal approach in the past to the challenge of maintaining healthy skin and avoiding breakdown has been prevention. For example, patients restricted to bedrest, a subject population at high risk of pressure ulcer formation, will be turned frequently by the nursing staff to relieve prolonged pressure. Mattresses designed to cyclically change the distribution of pressure have been developed. Similarly, custom-designed wheelchair cushions are manufactured to help distribute the load more evenly. Further, patients in wheelchairs are taught to conduct pressure releases regularly to prevent breakdown. Patients with altered sensation use timers to indicate when pressure releases should be conducted, and they undergo extensive educational programs to encourage effective prevention practices. For patients with limb deficiencies, orthoses and prostheses are custom-designed so as to distribute forces properly at the body support interface in a manner that avoids skin breakdown. Thus, current prevention programs are designed to reduce force levels and loading durations below those that cause breakdown.
Ideally, tissue pressure management and prevention programs would eliminate all skin breakdown. However, attempting to reduce force levels and durations conflicts with life and functional activities. Mechanical forces and/or load durations are now induced in regions...