Registered Nurses´ Association of Ontario
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Pressure Redistribution
Pressure (Interface):
The force per unit area that acts perpendicularly between the body and the support surface. It is affected by the stiffness of the support surface, the composition of the body tissue, and the geometry of the body being supported (AHCPR, 1994).
Pressure Redistribution:
The ability of a support surface to distribute load over the contact areas of the human body (National Pressure Ulcer Advisory Panel, 2006). The goal of this approach is to create an even interface pressure over the entire contact area, to reduce the overall pressure and avoid areas of focal pressure. In the past, the terms pressure reduction and pressure relief have been used to descript this approach.
Pressure Reducing Surface:
An outdated term that traditionally describes a surface that reduces the interface pressure between the body surface and the resting surface, but does not consistently maintain pressure below capillary closing pressure (AHCPR, 1994; Mulder, Fairchild & Jeter, 1991; WOCN, 1987).
Pressure Relieving Surface:
An outdated term that traditionally describes a surface that consistently reduces the interface pressure between the body surface and resting surface below capillary closing pressure (AHCPR, 1994; Mulder et al., 1991; WOCN, 1987).
Indications:
- To prevent skin breakdown, or further skin breakdown.
- To promote healing in the patient who already has skin breakdown involving multiple surfaces (Bryant, 1992).
There are seven basic requirements that a support surface must meet in order to prevent pressure and shear. The surface must: - Conform to bony prominences without resistance;
- Not have significant memory;
- Allow patient immersion;
- Not “bottom out”;
- Relieve shear caused by patient movement;
- Prevent skin maceration; and
- Provide patient comfort (Jay, 1995).
- To determine if a patient has bottomed out, the caregiver should place an outstretched hand (palm up) under the mattress overlay below the part of the body at risk for ulcer formation.
- If the caregiver can feel that the support material is less than an inch thick at this site, the patient has bottomed out.
- Bottoming out should be checked at various anatomical sites and while the patient assumes various body positions.
- Overlay mattresses are devices that are applied over the surface of the hospital mattress. Most overlays provide pressure reduction. Overlays may be static (foam, gel, water, air filled) or dynamic (low air loss, alternating air).
These support surfaces remain motionless except in response to body movement and seek to redistribute the body weight by shifting the extra weight or load from areas with bony prominences to areas under low pressure (Holzapfel, 1993).
When selecting a static support surface made of foam, consider the following characteristics of foam: stiffness, density and thickness. Indentation load deflection (ILD) is a measure of stiffness. Typical values for foam mattress overlays would be a 25% ILD of 30 lbs., a density of 1.3 pounds per cubic foot, and thickness of 3 to 4 inches (Kemp & Krouskop, 1994).
Use a static support surface if a patient can assume a variety of positions without bearing weight on a pressure ulcer and without “bottoming out” (AHCPR, 1994).
Dynamic Devices
Use a dynamic support surface if the patient cannot assume a variety of positions without bearing weight on a pressure ulcer, if the patient fully compresses the static support surface, or if the pressure ulcer does not show evidence of healing (AHCPR, 1994).
Dynamic devices have moving parts and are attached to an electrical power source. These devices compensate for the motionless or compromised body movement by shifting the weight or load from areas with bony prominences to areas under lower pressure. If a patient has large Stage III or IV pressure ulcers on multiple turning surfaces, a low-air loss bed or an air-fluidized bed may be indicated (AHCPR, 1994).
When excess moisture on intact skin is a potential source of maceration and skin breakdown, a support surface that provides airflow can be important in drying the skin and preventing pressure ulcers (AHCPR, 1994). Moist skin is more likely to abrade and blister.
