Effective Support Surface Selection in Preventing and Treating Pressure Ulcers

Kevin Y. Woo, BSc, MSc, PhD, RN, GNC(C), ACNP, FAPWCA

Pressure ulcers are a significant problem across the continuum of health care settings, especially in vulnerable populations such as individuals at the end of life. In 2009, the overall prevalence was 12.3% (N=92,408) in the United States, according to a national survey.1 The burden of pressure ulcers is significant; the average cost associated with the treatment of deep pressure ulcers and related complications is US $129,248 in acute care. People with pressure ulcers are beset by limited mobility, social isolation, depression, and persistent pain. In reviews of 53 studies, support surfaces (e.g., medical-grade sheepskin, high-specification foam mattresses) have been recognized as reducing the incidence of pressure ulcers. Appropriate surfaces or mattresses facilitate pressure redistribution, remove pressure to injury-prone areas (especially bony prominences) and spread weight evenly to avoid pressure buildup. Foam, gel-filled, water-filled and low air loss mattresses are commonly used. They are considered "reactive" because the effect of pressure redistribution is determined by the surface area of the body in contact with the mattress; the larger the area of the body that is supported by the mattress, the lower the pressure at any given point of contact.

The majority of specialty surfaces are expensive, but taking into account the number of ulcers that can be prevented, the calculated cost of using therapeutic surfaces and other preventive measures is approximately 1/40th that of the standard care approach.2 Amid the wide variety of options, clinicians should understand how to make the selection of the right mattress/surface for the individual (which?), the right clinical indication/circumstances (when?) and the right length of time (how long?) to get the right health outcomes (what to expect?). The mnemonic MATTRESSES highlights 10 key factors that should be considered prior to using a support surface to ensure the cost-effective use of resources to prevent pressure ulcers. The comfort and management of wound symptoms of individuals receiving palliative care should weigh heavily in the selection of support surfaces for these people.


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How to Select a Surface: Think MATTRESSES

M—Microclimate and Moisture: Increasing attention has been drawn to the role of "microclimate" in pressure ulcer care. Microclimate refers to the environment at or near the skin surface that is influenced by the combined effect of skin temperature, humidity/moisture and air movement. An increase of 1°C in skin temperature results in an increase of approximately 13% in tissue oxygen demand, making the skin more vulnerable to mechanical damage. Excess moisture from incontinence, sweating and wound exudation can cause skin maceration, weakening the connections between epidermal cells and collagen fibers. The interruption of normal barrier function increases skin permeability to irritants and pressure damages. Certainly, heat and moisture accumulation are directly related to air movement at the interface between the skin and the support surface. Some foam mattresses have poor heat properties and tend to "hug" the body, limiting airflow. In contrast, low air loss or air-fluidized beds (with vapor-permeable covers) promote air circulation that cools the skin through convection and evaporation of moisture from the skin. This type of mattress may be beneficial for individuals with severe burns. Other simple measures to control the microclimate include reducing the layers of pads underneath the individual as well as using clothing, incontinent briefs and coverings that are breathable (avoid plastic). It is important to monitor the skin hydration status to avoid excessive dryness that can also cause skin breakdown.

A—Activity Levels: Accumulating evidence suggests that people with restricted physical activities and restricted mobility are at risk for pressure ulcers. Norton and colleagues proposed that activity levels be considered when selecting a support surface.3 To optimize activities, clinicians must be aware that certain therapeutic support surfaces (e.g., foam, gel-filled and air-fluidized mattresses) tend to mold around body contours (envelopment) and allow the body to sink into the surface (immersion), compromising the person's ability to get in and out of bed and his or her independence.

T—Tissue Tolerance: Skin breakdown is inevitable when metabolic demand outstrips the supply of oxygen and vital nutrients. The extent and severity of tissue injury are, however, dependent on a number of intrinsic factors that predispose individuals to the development of pressure ulcers. Some of these key factors are poor nutritional intake, low body mass index (

T—Total Body Weight: Pressure and other mechanical forces compress, stretch and distort the normal alignment of the soft tissue, potentially leading to injury. The impact of mechanical distortion of the tissue is more pronounced in individuals who are emaciated. In one study, the maximum shear force at the coccyx was higher (p4 On the other extreme of the body weight spectrum, bariatric individuals are also at high risk for pressure ulcer development due to the substantial stress that is put on the skin. Individuals with either high or low BMI should be carefully evaluated for a support surface that can prevent skin breakdown.

R—Repositioning Needs: Although frequent repositioning is deemed essential to managing pressure, it is not always feasible in critically ill individuals, because positioning may precipitate vascular collapse or exacerbate shortness of breath (as with, e.g., advanced heart failure). A therapeutic surface is recommended for those who cannot tolerate either frequent repositioning or having the head of the bed lower than 30 degrees (due to dyspnea or in order to prevent aspiration during enteral feeding). The turning frequency can be reduced by the use of redistributing support surfaces; however, prolonged exposure to low pressure can be equally damaging to tissue. Clinicians must not forget there is a need for repositioning immaterial of the type of mattresses or specialty surfaces being utilized.

E—Edema: Edema, which stretches the skin and impairs the delivery of oxygen, is considered a risk factor for skin breakdown. By alternating air pressure in compartments of the mattress under the torso and leg in a way that emulates the body’s natural intermittent movements, massage movements have been demonstrated to increase lymph flow that may aid edema management.5 However, alternating air mattresses must be used with caution; they can cause serious injuries in individuals with spinal instability and exacerbate symptoms such as motion sickness, protracted pain and nausea. Individualized assessment is warranted. Severe edema may lead to fluid leakage or "weeping" through the skin that may benefit from low air loss and air-fluidized support surfaces that draw moisture into the air to keep skin dry.

S—Shear and Friction: Development of pressure ulcers is a dynamic and complex process that involves the combined effect of mechanical forces, including shear and friction, in addition to pressure. Pressure is defined as the perpendicular force that is applied to the skin, distorting and compressing underlying soft tissues, especially over bony prominences.6 Shear or shear stress is produced by displacement or deformation of tissue, usually in a diagonal direction, that alters the original alignment of tissue as one layer of tissue and the deeper structure slide in opposite directions (bony skeleton moving in an opposite direction to the surface skin). Deformation disrupts the cell structure, obstructs lymphatic drainage, reduces blood flow and potentiates ischemia. In contrast, friction describes the resistance to movement created between two surfaces such as the superficial layers of skin and the adjoining support surface. By simply instituting measures to reduce friction, up to 16% of pressure ulcers can be prevented.7

S—Symptom Management: A support surface is often considered for individuals receiving palliative care to promote comfort. The primary purpose may not be pressure ulcer prevention but rather ensuring comfort at the end of life.

E—Existing Pressure Ulcer(s): Individuals with an existing pressure ulcer are usually at risk for developing further skin breakdown. For those who have multiple ulcers, a support surface should be considered in order to address the lack of turning surfaces.

S—Sites: One of the areas that is most vulnerable to pressure-related skin damage is the heel. The heel has a pointed shape with a limited surface area of contact to redistribute pressure; when this is combined with the low subcutaneous tissue volume, this area is prone to pressure damage. Heel tissue is enveloped within the fibrous septa that allow pressure to build up easily and occlude vascular supply. Boots with the heel area cut out to allow the heel to be completely lifted off the surface are useful in preventing and treating pressure ulcers. Many different heel boots and positioning devices are available; however, no one device works best in all circumstances. Special attention must be paid to potential damage to the lower leg areas where the pressure is redistributed.

Health care professionals should determine the individual's support surface needs by applying these selection principles to their assessment. The treatment goals can define an effective management strategy that addresses the therapeutic role of the support surface, whether it be primarily for prevention, symptom management, shear reduction or other wound care challenges.


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