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Choosing the right pressure-relieving mattress

Una Adderley
Tissue Viability Prescribing Specialist Nurse Scarborough, Whitby and Ryedale PCT

The prevalence of pressure ulcer damage in the community is uncertain; however, up to 10% of hospital patients may suffer pressure ulcer damage.(1) The sacrum is the most common site for pressure damage, followed by heel ulceration. Other common sites include the hips, buttocks and elbows.
The impact on quality of life is unknown, but anyone who has cared for a patient with a pressure ulcer will be aware of the misery and frustration it can cause. Treatment of pressure ulcers is often prolonged and therefore expensive.

Risk factors
Certain intrinsic patient factors, such as reduced mobility and sensory impairment, are known to increase the risk of pressure ulcer damage. However, other intrinsic factors, such as acute illness, reduced level of consciousness, extremes of age, impaired nutrition, vascular disease, severe chronic or terminal illness, and a past history of pressure damage, are also believed to increase the risk of pressure damage.
It can be difficult to have a swift impact on these factors. Although improving a patient's diet will reduce the risk of pressure ulceration, immediate results are highly unlikely. In the meantime, the patient's level of risk may remain high. However, the risk of pressure ulceration can be immediately reduced by addressing the extrinsic factors that increase the risk of pressure damage, such as pressure, shearing, friction and moisture.

Risk assessment
Nurses have a responsibility to identify patients at increased risk, monitor their skin condition, act quickly if early signs of skin damage are detected, and target interventions to those at risk or with signs of early damage. A high-quality assessment will ensure that patients receive the intervention and equipment most suited to their needs.
A formal risk assessment should be undertaken for all patients perceived as being at potential risk of pressure ulceration. It should combine skin inspection, the use of a recognised risk assessment tool (eg, the Waterlow scale) and clinical judgement, and be properly documented. Patients judged as being at significant risk should have the skin condition of their pressure areas reassessed at least daily, or more often if signs of damage occur. It is important to remember that the aim of a risk assessment is to determine action, and that it is not an end in itself.
A skin inspection will check for signs of early damage such as persistent erythema (redness) or nonblanching hyperaemia (redness that does not turn white when fingertip pressure is applied). Signs of advanced pressure damage include blistering, discoloration, localised heat and oedema or induration (marking). Erythema may be more difficult to see in darkly pigmented skin where skin damage may present as purplish/bluish localised areas of skin with localised heat, which, if tissue becomes damaged, is replaced by coolness.
Several risk assessment tools are in common use (eg, the Waterlow scale, Braden scale and Norton scale). Unfortunately, at present there is insufficient epidemiological evidence to fully identify and quantify the factors that increase the risk of pressure ulceration. So, although these scales are a useful aide-mémoire for identifying possible risk factors, at present none of the scales can be regarded as being a valid and reliable predictor of risk.(2)
In the absence of valid and reliable risk assessment tools, clinical judgement continues to play an essential role in assessing risk. In addition to assessing the likely impact of the intrinsic patient factors identified above, clinical judgement will also need to address extrinsic factors that impact on the degree of pressure, shearing and friction the patient may face. Patients receive care in a variety of environments. In a nursing home, an immobile patient can be assisted with manual repositioning at frequent intervals. A patient with a similar level of immobility but who is receiving care within their own home may not be able to receive such frequent intervention.
The knowledge and skill of the patient and their carers will affect care. A patient who has received specific training in preventing pressure ulceration will be able to identify how frequently they need to be repositioned and ensure this happens. However, when a patient's cognitive state means that they are unable to recognise or communicate their needs, this role will fall to the registered nurse or carer. Risk assessment and care also need to include a prediction of how the patient's condition may change in the near future. The pressure ulcer prevention needs of a patient receiving palliative care at home are likely to significantly increase as the patient enters the terminal stage of their life.

The role of manual repositioning
Pressure-reducing equipment can greatly reduce a patient's risk of developing a pressure sore but should not be viewed as a replacement for frequent repositioning. Manual repositioning not only relieves pressure but also enables the carer or clinician to carry out frequent skin inspections and can promote a patient's comfort. Pressure-relieving equipment is unlikely to be a cost-effective means of reducing the need for manual repositioning if a carer is available 24 hours a day.
Unfortunately, some patients will remain vulnerable to developing pressure ulcers, even when frequent manual repositioning is carried out. These patients will need the additional assistance of pressure-relieving equipment. There are also some situations where frequent manual repositioning is undesirable or impossible. Patients with advanced disease may seek minimal physical intervention, despite optimal analgesia. Patients living in their own home may also be unable to access frequent manual repositioning.

Selection of pressure-relieving equipment
If frequent manual repositioning is either impossible or insufficient to prevent pressure damage, then the nurse will need to decide which pressure-reducing device is most likely to benefit the patient. A patient who is nursed mostly in bed may benefit from a pressure-relieving mattress, but someone who spends a considerable amount of time out of bed will also need a pressure-reducing cushion.
Seating assessment is a complex area that should be undertaken by a trained assessor with specialist knowledge, such as a physiotherapist or occupational therapist. The assessment of seating to prevent pressure ulceration needs to consider distribution of weight, postural alignment and support of the feet, rather than simply selecting which pressure cushion to place under a patient. However, it is unrealistic to expect the stretched resources of the occupational therapist or physiotherapist to assess every patient who develops a vulnerable sacrum. Community nurses should equip themselves with the knowledge and skill to provide assessment and advice for the less complex needs of this group of patients.
The wide variety of pressure-relieving mattresses on the market can make selection a bewildering experience. It is useful to divide pressure-relieving mattresses into three broad groups: static mattresses or overlays, alternating pressure mattresses or overlays, and low-airloss/ air-fluidised systems. This last group are mainly used in intensive care units or burns units and are unlikely to be required within a community setting.
Static devices can be made from foam or viscose or filled with air, water, fibre, gel or beads. They work by moulding around the patient and thereby reduce pressure on pressure points by increasing the area of contact between patient and support surface. Alternating devices have one or two layers of air cells that are alternately inflated and deflated, providing alternating pressure and then pressure relief for each area of skin.
Costs vary enormously, but there is no clear evidence as to which mattresses or overlays are the most effective. A systematic review found that foam alternatives to standard hospital mattresses were more effective in prevention of ulceration in at-risk patients, but there was no obvious best foam alternative. The same review reported that the relative merits of constant low pressure and alternating pressure were unclear.(3)
Clinicians face a difficult dilemma. Although they have a responsibility to provide the best care for the individual patient, they also have a responsibility to ensure that the public purse is spent in the most effective way possible. It is financially irresponsible to provide an expensive high-specification device if the patient does not require it.
In the absence of clear guidelines, it is useful to adopt a "step up, step down" approach. Clinicians should carry out a full assessment and then, if required, select the product most suitable for their patient at that time. If the patient's condition deteriorates then it may be necessary to "step up" to a higher-specification device. Alternatively, an improvement may prompt "stepping down" to a lower-specification device. This approach does involve an element of risk, which can be minimised by ensuring that patients are closely monitored and by documenting the rationale for each decision in the patient's notes.
In addition to choosing between static and alternating devices, the clinician is required to choose between replacement mattresses and overlays. Overlays are placed on top of an existing mattress. Some patients find the extra height a useful aid when getting out of bed, and carers may appreciate the additional height too. However, some overlays are sufficiently bulky to prevent a patient's partner from continuing to share a bed with the patient. Concern has also been expressed that overlays may slip or render bed rails ineffective.
Replacement mattresses can be more securely fastened to a bed. However, in small homes it may be difficult to find storage for the original mattress that the pressure-relieving device has replaced. A single replacement mattress placed on a double-bed base may also deprive the patient's partner of somewhere to sleep, and although double replacement mattresses are available, some trusts are unwilling to fund these.
Although the selection of equipment can be complex and potentially costly, adopting a structured and informed approach will maximise the chances of effective and cost-effective provision of care.


  1. Clark M, Watts S. The incidence of pressure sores within a National Health Service Trust hospital during 1991.J Adv Nurs 1994;20:33-6.
  2. National Institute for Clinical Excellence. Pressure ulcer prevention. Clinical guideline 7. London: NICE; 2003.
  3. Cullum N, Deeks J, Sheldon TA, Song F, Fletcher AW. Beds, mattresses and cushions for pressure sore prevention and treatment (Cochrane Review). In: The Cochrane Library, Issue 1. Chichester: John Wiley & Sons; 2004.