1.11 Pressure Ulcer Prevention
1.11.2 Support Surfaces
As pressure (and shear) is the primary cause of pressure ulcer development (NPUAP/EPUAP 2009) much effort is made to reduce this for immobile patients in clinical practice. This is achieved by the provision of specialist support surfaces (mattresses and cushions) and repositioning the patient. Support surfaces are used to reduce pressure to vulnerable skin sites. These either mould to the patients’ body, dispersing their weight over a large area providing ‘constant low pressure’ (McInnes et al. 2011) or they mechanically vary the pressure beneath the patient, so reducing the duration of the applied pressure (alternating pressure mattresses). Constant low pressure mattresses include those made of foam, foam and air, foam and gel, profiled foam, hammocks, air suspension, water suspension and air- particulate suspension/air fluidised (McInnes et al. 2011). The most commonly encountered constant low pressure mattresses in clinical practice are made from foam and are classified as ‘low tech’ devices (i.e. of a lower technical specification). Alternating pressure devices involve the inflation and deflation of air filled cells and are available as cushions, mattress overlays, single or multi-layer mattress
replacements and are classified as ‘high tech’ devices (i.e. of a high specification) (McInnes et al. 2011). Some support surfaces also assist with the management of heat and moisture (Clark et al. 2010).
The use of pressure relieving equipment has implications for patients quality of life. A qualitative study of patients who live with pressure ulcers reported the impact of alternating pressure mattresses on patient’s pain was considerable (Hopkins et al. 2006). Another study comparing alternating pressure overlay mattresses with alternating pressure replacement mattresses found that some patients found the mattresses uncomfortable, noisy and reported difficulties in moving in bed (Nixon et al. 2006a). It is therefore important to consider the patients personal circumstance and preferences and involve them in the decision making process when making equipment choices.
A Cochrane review of the effectiveness of support services on the prevention of pressure ulcers was undertaken which included 53 studies evaluating the
effectiveness of various mattress types (McInnes et al. 2011). The review identified limitations in the literature including poor study quality and the lack of definition of standard hospital mattresses in many of the primary studies making interpretation
difficult. However, for the five studies that compared foam alternatives with the standard hospital foam mattresses the results were pooled (RR 0.40 95% CI 0.21 to 0.74) and a separate UK study analysis (RR 0.41; 95% CI 0.19 to 0.87) was
undertaken (where variation in the term ‘standard hospital mattress’ was less likely) where the significant benefit of alternative foam over standard foam was
maintained. Due to continued heterogeneity a further analysis was undertaken (excluding one study which included grade 1 pressure ulcers) which still favoured the alternative foam support (RR 0.29 95% CI 0.16 to 0.52) but there was
inadequate evidence of which specific alternative foam mattress was superior (McInnes et al. 2011).
The review also considered comparisons between alternating pressure mattress’s and standard hospital mattresses and constant low pressure and alternating pressure mattresses (McInnes et al. 2011). The alternating pressure and standard hospital mattress comparison, involved two studies which indicated a statistically significant reduction in pressure ulcer development in the alternating pressure mattress group (RR 0.31; 95% CI 0.17 to 0.58). However this should be interpreted cautiously as the studies were at high risk of bias. The constant low pressure and alternating pressure mattress comparison was considered in 10 studies but the advantages of one over the other remains unclear (McInnes et al. 2011). This has important clinical implications as both constant low pressure and alternating pressure devices are routinely used in clinical practice yet evidence about the benefits of one over the other is lacking. The financial implications and potential savings related to equipment choices are substantial, with the unit cost for constant low pressure high specific foam mattress being £18-£600, while the unit cost for an alternating pressure replacement mattress is £1000-£5000.
The Cochrane review (McInnes et al. 2011) was recently adapted and updated by NICE (2014) to consider the most clinical and cost-effective pressure re-distributing device for pressure ulcer prevention, to inform their clinical guideline. NICE
acknowledged the limited evidence of effectiveness for redistributing devices and recommended this as a key research priority (NICE 2014).This work is being taken forward by the PRESSURE 2 (ISRCTN01151335) study which is currently in
progress and is comparing high specification foam with alternating pressure mattresses.
In light of equipment related findings the recent NICE guidance makes the following recommendations for pressure ulcer prevention ((NICE 2014), Section 5.3)):
• ‘the use a high-specification foam mattress for adults who are admitted to secondary care
• the use a high-specification foam mattress for adults who are assessed as being at high risk of developing a pressure ulcer in primary and community care settings
• Consider a high-specification foam theatre mattress or an equivalent pressure redistributing surface for all adults who are undergoing surgery.
• Consider the seating needs of people at risk of developing a pressure ulcer who are sitting for prolonged periods.
• Consider a high-specification foam or equivalent pressure redistributing cushion for adults who use a wheelchair or who sit for prolonged periods’.
There is further guidance for adults with an existing pressure ulcer including that the ‘use of a dynamic support surfaces should be considered for adults with a pressure ulcer, where the use of high-specification foam mattresses is not sufficient to redistribute pressure’ (NICE 2014).
In addition to mattresses and cushions there are also some pressure relieving devices which have been developed to reduce pressure to heels. Guidance indicates that heel devices should ‘elevate the heel completely in such a way as to distribute the weight of the leg along the calf without putting pressure on the Achilles tendon. The knee should be in slight flexion’ (hyperextension of the knee may cause obstruction to the popliteal vein predisposing a deep vein thrombosis). (NPUAP/EPUAP 2009).
NICE (2014) recently undertook a systematic review in relation to heel devices for pressure ulcer prevention. The review involved 16 studies which compared the effectiveness of different devices on heel pressure ulcer development. Due to the limited evidence of effectiveness of any one device, NICE recommends that for adults at high risk of developing a heel pressure ulcer strategies to offload heel pressure should be discussed with the patient and where appropriate their family or carers, as part of an individualised care plan (NICE 2014).