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Preventing pressure ulcers: choosing a mattress

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Heidi Guy, RGN.

Tissue Viability Nurse, Pirton Wards, at Lister Hospital, Stevenage, Hertfordshire

Pressure ulcers are a costly health consequence, both in terms of personal suffering and economics (Cullum et al, 1995). 

In 1992 the Health of the Nation Targets set by the Department of Health recommended an annual reduction in pressure ulcer incidence of 5-10 %. However. a recent European prevalence study, albeit using a different indicator of frequency, demonstrated a UK hospital prevalence of 21% (Clark et al, 2002). The incidence of pressure ulcers remains high in spite of the introduction of specific benchmarks for pressure area care (DH, 2001).

Pressure ulcers can potentially develop in all age groups, with both intrinsic and extrinsic factors contributing to the risk (see box). It is believed that most can be prevented, although there is debate about whether a minority of ulcers are inevitable (Bliss, 2000; Fox 2002).

As with many health consequences it is necessary to determine a patients’ risk of developing a pressure ulcer. There are several risk assessment tools, which can be used for this purpose, for example Braden (Bergstrom et al, 1998) and Waterlow (1996; www.judywaterlow.fsnet.co.uk/). There is limited evidence (RCN, 2001) to show that one tool is more effective than another. NICE (2001) advises that risk assessment tools be used as an memory aid and do not replace clinical judgement.

Risk assessment tools may categorise a patient as no risk, low risk, medium risk, at risk, high risk, very high risk. NICE (2003) make defining risk easier by describing patients as either ‘vulnerable to pressure ulcers’ or ‘at elevated risk of pressure ulcers’.

Pressure ulcers can be prevented by removing the factors leading to their occurrence. It is not always possible to remove intrinsic factors. However, pressure, shear and friction can be reduced or eliminated by considering patient positioning and by employing the correct support system. Support surfaces on both the bed and chair need to be considered.

Risk assessment

Risk assessment itself has not been shown to provide conclusive evidence of whether a patient will develop a pressure ulcer. Therefore clinical judgement must be used. For example if risk assessment has calculated that a patient is not at risk, but erythema due to pressure occurs after a period of time on a certain support surface, then clinical judgement would deduce that a higher specification surface should be employed.

Skin assessment is a valuable method of determining risk or the beginning of pressure damage. The first indication of potential pressure injury may be an area of redness (erythema) that blanches under light finger pressure. If the erythema does not blanch, then this area is classified as a Grade 1 pressure ulcer (EPUAP, 2004). However, in darkly pigmented skin other signs may need to be used, such as a firm or boggy feel to the skin (NPUAP, 2004). Areas most at risk of developing damage are over bony prominences.

Patients who already have pressure damage will need a pressure-relieving mattress on their bed. Often the type of mattress is determined by the severity of the damage. There are several pressure ulcer grading tools, for example Stirling (Reid and Morrison, 1994) and Torrance (1983), but, for the purpose of this article, the European Pressure Ulcer Advisory Panel Grading Tool has been used (EPUAP, 2004).

NICE (2003) recommends that any patient at risk or undergoing surgery has, at the very least, a pressure-reducing foam mattress on their bed. Patients at elevated risk should be nursed on a high technology mattress (NICE, 2003).

Pressure-reducing/relieving mattresses are used in conjunction with repositioning to reduce the risk of pressure damage occurring. Repositioning schedules need to be determined on an individual basis, but must not be excluded because a mattress has been employed.

Support systems

Beds

Beds range from a two-section manual, such as the King’s Fund model commonly seen in our hospitals, to four-section electric profiling beds. These increase patient independence, significantly reduce manual handling needs and reduce shear and friction when used in the fully profiled position. Most mattresses are now compatible with profiling beds, but this would need to be confirmed with the manufacturer before a mattress is used with one of these beds.

Types of support surface

Support surfaces are often described as pressure reducing, pressure redistributing or pressure relieving. Reducing indicates that the surface uniformly reduces the pressure over a greater surface area. Redistributing indicates that high pressure points are redistributed to create an even pressure distribution. These two types of surface definitions are synonymous.

Relieving indicates that the surface completely relieves pressure for periods of time and only applies to alternating systems.

The support surface can be a base mattress lying directly on the bed frame, an overlay which lies on top of the base mattress or a replacement which lies directly on the bed frame.

Standard foam mattress

This type of mattress is suitable for patients not at risk of pressure damage. This includes patients who are not expected to enter into an episode of care, such as surgery, that may temporarily increase their risk. Evidence suggests that the standard hospital foam mattress provides insufficient pressure relief (Cullum et al, 2004).

Higher specification pressure reducing foam mattress

These are required for patients vulnerable to pressure ulcers.

These mattresses tend to be made of higher density foam or visco-elastic foam which conforms to the body contours. Cullum et al (2004) suggest that these types of mattress provide superior pressure reduction to the standard hospital foam mattress. Shear and friction may also be reduced with this type of surface. They often come with an extended warranty, against foam collapse, of up to seven years, depending on the manufacturer/company provider.

Non-dynamic overlays

Non-dynamic overlays are indicated for patients vulnerable to pressure ulcers. They may be made of foam, fibre or filled with foam chips. The life expectancy of overlays is often less than that of the higher specification pressure-reducing foam mattresses. Hence this option is often less economical than replacing the standard foam mattress with a pressure-reducing foam mattress.

For patients at elevated risk of pressure ulcers a viscous fluid-filled overlay may be considered. These are also suitable for patients with pressure damage. This type of overlay reduces shear, friction and pressure and can be useful when an electrical power supply is limited, unavailable or unreliable.

Dynamic pressure-relieving mattresses

These systems provide periods of pressure relief to the body in a cyclical mode. Two to four cells (depending on manufacturer) will cyclically alternate between inflation and deflation, usually over a timeframe of seven to 10 minutes.

They may be overlays or replacement systems. There is little evidence to suggest one manufacturer’s product is more superior to another (Cullum et al, 2004). Therefore product selection may come down to cost analysis, company support, mattress specifications and local factors.

Some alternating mattresses have an altered section for the heels, with smaller air cells offering improved pressure relief for this highly vulnerable area.

Some of these mattresses need to have the pressure levels set according to the patient’s weight, others automatically adjust themselves according to weight and position. There is often an upper patient weight limit.

Alternating overlays - These mattresses lie on top of the base mattress and are made up of one layer of air cells. Patients who are vulnerable to pressure damage or with a Grade 1 or 2 pressure ulcer may benefit from this type of system. In the event of power loss the mattress may deflate, leaving the patient lying on a flat mattress on top of the base foam mattress. For this reason, they may not be a suitable choice for patients at elevated risk or those with Grade 3 or 4 pressure ulcers.

Replacement mattresses - Replacement mattresses are designed for patients at elevated risk or those with Grade 3 or 4 pressure damage. These systems may also be employed for heavier patients for whom other mattresses are unsuitable. They are made up of a double layer of air cells, or air cells and foam, and lie directly on the bed frame.

Low-air-loss mattresses - These mattresses inflate at a constant low pressure that adjusts to the patient’s weight and position by allowing air to pass through tiny holes. They are suitable for patients at elevated risk or with Grade 3 or 4 pressure ulcers. These mattresses are also useful for patients who cannot tolerate the alternating movement of air cells on the other pressure-relieving systems. Patients with bony metastases often find these mattresses more comfortable, for example.

Air-fluidised bead beds

These allow patients to float freely, thereby eliminating pressure, shear and friction. These beds may be employed in critical care situations where the patient has heavily exuding wounds or burns, because body fluids can drain directly into the bed and be filtered, thus making excessively high exudate levels more manageable. They are exceptionally heavy beds, weighing approximately one ton, which makes them unemployable on floors that cannot support their weight. They can also be aesthetically unpleasing to some patients.

Specialist support surfaces

These offer specialist therapy as well as relieving pressure. These are usually used in units such as intensive care or spinal injury and may offer rotational or percussion therapy.

Conclusion

The selection of the correct support system for each individual involves many factors and can therefore be quite complex. Decisions, as well as centering around the risk of the patient and being based on national guidance, will be made locally taking into consideration local population needs and cost analyses.

Author’s contact details
Heidi Guy, Tissue Viability Nurse, L20G, Lister Hospital, Stevenage Herts SG1 4AB. Email: heidi.guy@nhs.net


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