International Journal of Nursing Studies 49 (2012) 345–359
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Review
Preventing pressure ulcers—Are pressure-redistributing support surfaces effective? A Cochrane systematic review and meta-analysis§ Elizabeth McInnes a,*, Asmara Jammali-Blasi a, Sally Bell-Syer b, Jo Dumville c, Nicky Cullum d a
Nursing Research Institute – St Vincents and Mater Health Sydney & Australian Catholic University, National Centre for Clinical Outcomes Research (NaCCOR), Level 5, Delacy Building, 379 Victoria St Darlinghurst, NSW 2010, Australia b Cochrane Wounds Group, Department of Health Sciences, University of York, Heslington, York YO10 5DD, UK c Department of Health Sciences, University of York, Heslington, York YO10 5DD, UK d School of Nursing, Midwifery and Social Work, University of Manchester, Room 6.326, Jean McFarlane Building, Oxford Road, Manchester M13 9PL, UK
A R T I C L E I N F O
A B S T R A C T
Article history: Received 27 July 2011 Received in revised form 11 October 2011 Accepted 18 October 2011
Objectives: To undertake a systematic review of the effectiveness of pressure redistributing support surfaces in the prevention of pressure ulcers. Design: Systematic review and meta-analysis. Data sources: Cochrane Wound Group Specialised Register, The Cochrane Central Register of Controlled Trials, Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL. The reference sections of included trials were searched for further trials. Review methods: Randomised controlled trials and quasi-randomised trials, published or unpublished, which assessed the effects of support surfaces in preventing pressure ulcers (of any grade), in any patient group, in any setting compared to any other support surface, were sought. Two reviewers extracted and summarised details of eligible trials using a standardised form and assessed the methodological quality of each trial using the Cochrane risk of bias tool. Results: Fifty-three eligible trials were identified with a total of 16,285 study participants. Overall the risk of bias in the included trials was high. Pooled analysis showed that: (i) foam alternatives to the standard hospital foam mattress reduce the incidence of pressure ulcers in people at risk (RR 0.40, 95% CI 0.21–0.74) and Australian standard medical sheepskins prevent pressure ulcers compared to standard care (RR 0.48, 95% CI 0.31–0.74). Pressure-redistributing overlays on the operating table compared to standard care reduce postoperative pressure ulcer incidence (RR 0.53, 95% CI 0.33–0.85). Conclusions: While there is good evidence that higher specification foam mattresses, sheepskins, and that some overlays in the operative setting are effective in preventing pressure ulcers, there is insufficient evidence to draw conclusions on the value of seat cushions, limb protectors and various constant low pressure devices. The relative merits of higher-tech constant low pressure and alternating pressure for prevention are unclear. More robust trials are required to address these research gaps. ß 2011 Elsevier Ltd. All rights reserved.
Keywords: Pressure ulcer Prevention Review Hospital equipment Meta-analysis
What is already known about this topic? § This review is an abridged version of a Cochrane Review previously published in the Cochrane Database of Systematic Reviews 2011, Issue 4, doi:10.1002/14651858.CD001735. * Corresponding author. Tel.: +61 02 8382 3793; fax: +61 02 8382 3792. E-mail address:
[email protected] (E. McInnes).
0020-7489/$ – see front matter ß 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijnurstu.2011.10.014
Pressure ulcers are areas of localised damage to the skin and underlying tissue due to pressure, shear or friction. Pressure ulcers may affect those who are medically compromised, obese, pregnant and the elderly.
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Clinical and non-clinical settings use a variety of support surfaces to prevent the occurrence of pressure ulcers. What this paper adds Low-tech foam mattresses, sheepskins and operating table overlays are able to prevent pressure ulcers. There is insufficient evidence to draw conclusions on the value of seat cushions, limb protectors and various constant low pressure devices. Future trials investigating the effectiveness of support surfaces for preventing pressure ulcers should be robustly designed, paying particular attention to reporting follow-up times; attrition rates, intention to treat analysis, and giving adequate descriptions of interventions, comparators and definitions of pressure ulcer status. 1. Introduction Rationale: Pressure ulcers (also known as pressure sores, bed sores and decubitus ulcers) are chronic wounds involving areas of localised damage to the skin and underlying tissue, which are caused by pressure, or caused by both pressure and shear (European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, 2009). Pressure ulcers may develop in those who are seriously ill, neurologically compromised, or who have impaired mobility (Allman, 1997; Berlowitz et al., 1997; Bianchetti et al., 1993). Poor nutrition (Banks, 1998; Casey, 1998, 1997), obesity (Gallagher, 1997), poor posture and age (Rinda and Falce, 2002; Spoelhof, 2000; Thomas, 2001) have also been reported as increasing the risk of developing pressure ulcers. Studies conducted in healthcare facilities in Europe, Canada and the USA, report pressure ulcer prevalence ranges of 8–26% (Vanderwee et al., 2007a; Woodbury and Houghton, 2004). In Australia a national prevalence rate of 5–15% has been reported (Australian Commission for Safety and Quality in Health Care (ACSQHC), 2005). In Europe 58% of pressure ulcers and 70% in the USA are classified as Grade 2 and above (Vanderwee et al., 2007b; Van Gilder et al., 2009). A Grade 2 pressure ulcer involves partial thickness loss of the dermis and a pressure ulcer classified as Grade 2 or greater is a serious pressure injury requiring treatment (European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, 2009). There is some evidence that different grades of ulcer have different aetiologies and it is suggested that Grade 2 ulcers are due to friction and Grades 3 and 4 due to pressure and shearing forces (Lahmann and Kottner, 2011). Pressure ulcers are debilitating, painful and difficult to heal (Girouard et al., 2008). They are also associated with psychological, physical and social problems (Fox, 2002; Franks et al., 2002; Langemo et al., 2000), and have a detrimental impact on quality of life (Essex et al., 2009; Gorecki et al., 2009). The costs of preventing and treating pressure ulcers are high. Total annual costs for treating pressure ulcers in the UK have been estimated at between 1.4 and 2.1 billion pounds (Phillips and Buttery, 2009) and in the USA between 2.2 and 3.6 billion dollars (Van Gilder
et al., 2009). In Australia, the predicted number of bed days lost due to pressure ulcers incurred a median opportunity cost of AU$285 million (Graves et al., 2005a) and a median excess length of stay of 4.31 days (Graves et al., 2005b). The management of pressure ulcers is challenging for clinicians (Fox, 2002; Franks et al., 2002; Langemo et al., 2000) and pressure-redistributing support surfaces are commonly used as a means of prevention. Pressure redistributing support surfaces aim to reduce the magnitude and/or duration of pressure between an individual and the support surface used (interface pressure) in order to prevent or treat the pressure ulcer (European Pressure Ulcer Advisory Panel and National Pressure Ulcer Advisory Panel, 2009). Support surfaces include overlays, mattresses, cushions, sheepskins and beds. These can be classified either as ‘low tech’ devices, which are conforming support surfaces that mould around the shape of the patient to distribute the body weight over a large area and include constant low-pressure devices such as foam mattresses, or ‘high tech’ dynamic devices, such as alternating support surfaces where inflatable cells alternately inflate and deflate (McInnes et al., 2011). Some support surfaces such as turning beds/frames are mechanical and work by motor-driven turning and tilting. There are many such support surfaces available and prevention initiatives should be based on the best available evidence of effectiveness. Hence we have undertaken a systematic review of randomised controlled trials (RCTs) with the aim of providing clinicians with information on which to base decisions about choice of support surfaces for the prevention of pressure ulcers. Objective: To examine (1) which pressure-redistributing cushions, beds, mattress overlays and mattress replacements reduce the incidence of pressure ulcers compared with standard support surfaces and (2) how effective different pressure-redistributing surfaces are in preventing pressure ulcers, when compared with one another. 2. Methods Protocol and registration: The full Cochrane systematic review on which this article is based can be accessed from the Cochrane Database of Systematic Reviews (report number CD001735) (McInnes et al., 2011). This report adheres to the PRISMA method for reporting on systematic reviews (Moher et al., 2009). Eligibility criteria: RCTs and quasi-randomised trials comparing beds, mattresses, mattress overlays and cushions in any setting, on any clinical population, of any age, with any condition, which measured the incidence of new pressure ulcers. Trials which used only subjective measures of outcome (e.g. skin condition ‘‘better’’ or ‘‘worse’’) were excluded, as were trials which reported only proxy outcome measures such as interface pressure. Search Strategy (including information sources): We searched, without language, publication status or date restriction, the Cochrane Wounds Group Specialised Register (searched 8 December 2010); The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 4, 2010); Ovid MEDLINE (1950 to November Week 3, 2010); Ovid MEDLINE In-Process and
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Other Non-Indexed Citations (December 07, 2010); Ovid EMBASE (1980–2010 Week 48) and EBSCO CINAHL (1982 to 3 December 2010). The Ovid MEDLINE search was combined with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity- and precision-maximising version (2008 revision) (Lefebvre et al., 2009). The Ovid EMBASE and EBSCO CINAHL searches were combined with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN) (Scottish Intercollegiate Guidelines Network, 2009). The full electronic search strategy used in The Cochrane Central Register of Controlled Trials (CENTRAL) is presented in Box 1. Prior to conducting the electronic searches, experts were contacted to enquire about ongoing and recently published trials in the area of wound care. Citations within obtained reviews and relevant papers were scrutinised to identify additional trials. Study selection: The titles and abstracts of the search results were independently assessed for eligibility and relevance by two authors and the full copies of all potentially relevant trials were obtained. Decisions on final inclusion after full text assessment was made by one author and checked by a second; disagreements were
Box 1. Search strategy used in The Cochrane Central Register of Controlled Trials (CENTRAL).
#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14 #15 #16 #17 #18 #19 #20
#21 #22 #23 #24 #25
#26 #27 #28 #29 #30 #31
MeSH descriptor Beds explode all trees mattress* cushion* ‘‘foam’’ or transfoam overlay* ‘‘pad’’ or ‘‘pads’’ ‘‘gel’’ pressure NEXT relie* pressure NEXT reduc* pressure NEXT alleviat* ‘‘low pressure’’ NEAR/2 device* ‘‘low pressure’’ NEAR/2 support constant NEAR/2 pressure ‘‘static air’’ alternat* NEXT pressure air NEXT suspension* air NEXT bag* water NEXT suspension* elevation NEAR/2 device* clinifloat or maxifloat or vaperm or therarest or sheepskin or hammock or ‘‘foot waffle’’ or silicore or Pegasus or cairwave (turn* or tilt*) NEXT (bed* or frame*) kinetic NEXT (therapy or table*) net NEXT bed* ‘‘positioning’’ or ‘‘repositioning’’ (#1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 OR #12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 OR #23 OR #24) MeSH descriptor Pressure Ulcer explode all trees pressure NEXT (ulcer* or sore*) decubitus NEXT (ulcer or sore*) (bed NEXT sore*) or bedsore* (#26 OR #27 OR #28 OR #29) (#25 AND #30)
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resolved by discussion with a third author. Rejected trials were checked by a third author. Data collection process (including data items): Details of eligible trials were extracted by two review authors independently and summarised using a data extraction sheet. Disagreements were resolved by discussion with a third author. Data extracted from each study included patient characteristics, care setting, key baseline variables (age, sex, baseline risk, baseline area of existing ulcers), description of the interventions, number of patients randomised to each intervention, description of any cointerventions/standard care, follow-up period, outcomes and acceptability/reliability of equipment if reported. If data were missing from reports, attempts were made to contact the study author to complete the information necessary for the analysis and risk of bias assessment. If trials were published more than once, they were maximally data extracted and a primary reference cited. Risk of bias in individual trials: The methodological and reporting quality of each trial was assessed by a single author and checked by a second using a risk of bias assessment tool which addressed the fulfilment criteria as ‘low risk of bias’, ‘high risk of bias’ or ‘unsure’ (Higgins et al., 2009). This involved examining whether there was evidence of true randomisation; allocation concealment; baseline comparability of groups; blinded outcome assessment and intention-to-treat analysis. Eligible trials were also assessed for incomplete outcome data; drop-out rates and whether the study was free of selective outcome reporting. Disagreements were resolved by discussion with a third author. Summary measures (including synthesis of results): Analysis was conducted using RevMan software (Review Manager (RevMan) Version 5.0, 2008). If appropriate data were available from included trials, dichotomous variables of new pressure ulcers developed are presented as risk ratio (RR) with 95% confidence intervals (CIs). When continuous outcome variables, such as change in pressure ulcer size or time of pressure ulcer development, were measured, they were summarised using the mean difference (MD). Where possible, Grade 1 pressure ulcers (that is, those which resulted in non-blanchable redness of the skin) were separated from Grade 2 or higher pressure ulcers (Grade 2 generally refers to partial thickness loss of dermis and higher Grades 3 and 4, respectively, refer to full thickness tissue loss and full thickness tissue loss with exposed bone, tendon or muscle (EPUAP-NPUAP 2009)) in order to report on important clinical outcomes. Of the trials that included people with pre-existing pressure ulcers, only the incidence of new pressure ulcers was reported. Trials with similar patients, comparisons and outcomes were considered for pooled analysis. When there was more than one trial comparing similar devices using the same outcome measure (though possibly differing lengths of follow up), statistical heterogeneity was assessed using I2 and tested for by chi-squared test. A value of I2 greater than 50% indicated substantial heterogeneity and was considered significant where p < 0.10 (Higgins et al., 2003). In the absence of significant statistical heterogeneity, trials with similar comparisons were pooled using a fixed effect model (Higgins et al., 2011). Where there was substantial statistical heterogeneity we pooled the data using the
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random-effects model (Higgins et al., 2011). For the purpose of meta-analysis it was assumed that risk ratio remained constant for different lengths of follow up, hence we pooled trials which followed participants for different lengths of time. Where pooling was inappropriate, the results of the trials were reported narratively. 3. Results
Identification
Fifty-three eligible randomised trials were identified with a total of 16,285 study participants. Fig. 1 shows the study selection process. Of the 112 full-text articles assessed for eligibility, 59 were excluded for a variety of reasons as detailed in Fig. 1. The trials were conducted in a variety of settings including operating theatres, intensive care units, orthopaedic hospital units, accident and emergency units, extended care facilities and nursing homes. Sample sizes ranged from 12 to 1972 participants and the reported follow-up periods for trials ranged from one day to 12 months. Similar timing of outcome assessment
Records identified through database searching (n = 184)
between groups under investigation was reported in 34 trials and these ranged from daily to weekly. The methodological quality of the included trials is presented in Table 1. Use of a randomly generated allocation sequence was evident in 24 trials (Bennett et al., 1998; Cadue et al., 2008; Cooper et al., 1998; Economides et al., 1995; Gentilello et al., 1988; Geyer et al., 2001; Gilcreast et al., 2005; Kemp et al., 1993; Keogh and Dealey, 2001; Lazzara and Buschmann, 1991; McGowan et al., 2000; Mistiaen et al., 2009; Nixon et al., 2006, 1998; Price et al., 1999; Russell and Lichtenstein, 2000; Russell et al., 2003; Sanada et al., 2003; Santy et al., 1994; Schultz et al., 1999; Summer et al., 1989; Tymec et al., 1997; Vanderwee et al., 2005; Vyhlidal et al., 1997). Methods of randomisation used included table of random numbers, automated phone systems and computerised random number generators. Adequate allocation concealment – defined as those involved in enrolling participants not being able to foresee allocation through the use of central allocation, including telephone or web-based randomisation, or sequentially numbered, opaque, sealed envelopes – was evident in 16
Additional records identified through other sources (n = 11)
Included
Eligibility
Screening
Records after duplicates removed (n =195 )
Records screened (n = 195)
Full-text articles assessed for eligibility (n = 112)
Records excluded (n = 83)
Full-text articles excluded, with reasons (n = 59) Literature reviews (n=2) Incomplete data (n=8) Did not report clinical outcome (n=20) Not a trial (n=11) Different intervention (n=9) Other inclusion criteria not met (n=9)
Total trials in review (n = 53)
Fig. 1. PRISMA flow diagram of study selection.
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Table 1 Risk of bias of included trials. Study
Adequate sequence generation
Allocation concealment
Blinding
Incomplete outcome data addressed
Free of selective reporting
Groups similar at baseline
Timing of outcome assessment similar in all groups
Andersen et al. (1982) Aronovitch et al. (1999) Bennett et al. (1998) Cadue et al. (2008) Cavicchioli and Carella (2007) Cobb et al. (1997) Collier (1996) Conine et al. (1990) Conine et al. (1993) Conine et al. (1994) Cooper et al. (1998) Daechsel and Conine (1985) Economides et al. (1995) Ewing et al. (1964) Exton-Smith et al. (1982) Feuchtinger et al. (2006) Gebhardt et al. (1996) Gentilello et al. (1988) Geyer et al. (2001) Gilcreast et al. (2005) Goldstone et al. (1982) Gray and Campbell (1994) Gray et al. (1998) Gunningberg et al. (2000) Hampton (1997) Hofman et al. (1994) Inman et al. (1993) Jolley et al. (2004) Kemp et al. (1993) Keogh and Dealey (2001) Laurent (1997) Lazzara and Buschmann (1991) Lim et al. (1988) McGowan et al. (2000) Mistiaen et al. (2009) Nixon et al. (1998) Nixon et al. (2006) Price et al. (1999) Russell et al. (2000) Russell et al. (2003) Sanada et al. (2003) Santy et al. (1994) Schultz et al. (1999) Sideranko et al. (1992) Stapleton (1986) Summer et al. (1989) Takala et al. (1996) Taylor (1999) Theaker et al. (2005) Tymec et al. (1997) Vanderwee et al. (2005) Vyhlidal et al. (1997) Whitney et al. (1984)
Unclear Unclear Low risk Low risk Unclear Unclear Unclear Unclear Unclear Unclear Low risk Unclear Low risk Unclear High risk Unclear Unclear Low risk Low risk Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk Low risk Unclear Low risk Unclear Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Unclear Unclear Low risk Unclear Unclear Unclear Low risk Low risk Low risk Unclear
Unclear Unclear Unclear Low risk Unclear Low risk Unclear Unclear Unclear Unclear Low risk Unclear Low risk Unclear Unclear Unclear Unclear Unclear Low risk High risk Unclear Unclear Low risk Unclear Unclear Unclear Unclear Low risk Unclear Low risk Unclear Unclear Unclear Unclear Low risk Low risk Low risk Unclear Unclear Unclear Low risk Unclear High risk Unclear Unclear Unclear High risk Low risk Low risk Unclear Low risk Unclear Low risk
Unclear Unclear Unclear Unclear Low risk Unclear High risk Low risk Unclear Low risk Unclear Unclear Unclear Unclear Unclear Low risk Unclear Unclear Low risk High risk Unclear Unclear Low risk Unclear Unclear High risk Unclear High risk Unclear Unclear High risk Unclear Unclear High risk High risk Low risk High risk High risk Low risk High risk Unclear Unclear Low risk Unclear Unclear Unclear Unclear Unclear Low risk Unclear Unclear Unclear Unclear
Unclear Low risk Low risk Low risk Low risk Low risk Unclear Low risk Low risk Low risk Low risk Unclear Unclear Unclear Unclear Unclear Low risk Unclear Low risk Low risk High risk Unclear Unclear Unclear Unclear Unclear High risk High risk High risk High risk Low risk Unclear Low risk Low risk Unclear Low risk Low risk Unclear Low risk Low risk High risk Unclear Low risk Unclear Low risk Low risk Low risk Unclear Unclear Unclear Unclear Low risk Low risk
Low risk Low risk High risk Unclear Low risk Low risk Low risk Unclear Low risk Low risk Low risk Low risk Low risk Low risk High risk Low risk Unclear Unclear Low risk Unclear Low risk Unclear Unclear High risk Unclear High risk High risk High risk High risk High risk Low risk Low risk Low risk Low risk Unclear Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Unclear Low risk Low risk High risk Low risk Low risk Unclear Low risk Low risk
Low risk Low risk Low risk Low risk High risk High risk Unclear Low risk Low risk Low risk Low risk Low risk Low risk Unclear Low risk Low risk Low risk Low risk Low risk Unclear Low risk Unclear Unclear Low risk Unclear Low risk Low risk Unclear Unclear Low risk Low risk Low risk Low risk Low risk Low risk High risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Unclear Low risk Unclear Low risk Low risk Low risk Unclear Low risk High risk Unclear
Low risk Low risk High risk Low risk Low risk High risk High risk Unclear Low risk Low risk Low risk Low risk Low risk Low risk High risk Low risk Unclear High risk Low risk Low risk Low risk High risk Low risk Unclear Unclear Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Low risk Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Unclear Low risk
trials (Cadue et al., 2008; Cobb et al., 1997; Cooper et al., 1998; Economides et al., 1995; Geyer et al., 2001; Gray et al., 1998; Jolley et al., 2004; Keogh and Dealey, 2001; Mistiaen et al., 2009; Nixon et al., 2006, 1998; Sanada et al., 2003; Taylor, 1999; Theaker et al., 2005; Vanderwee et al., 2005; Whitney et al., 1984). Blinding of outcome assessment was reported in 10 trials (Cavicchioli and Carella, 2007; Conine et al., 1990, 1994; Feuchtinger et al., 2006; Geyer et al., 2001; Gray et al., 1998; Nixon et al., 1998; Russell et al., 2000;
Schultz, 1998; Theaker et al., 2005). Twenty-five trials adequately addressed incomplete outcome data, for example, by either having balanced or no missing outcome data, or having missing data that have been imputed using appropriate methods (Aronovitch et al., 1999; Bennett et al., 1998; Cadue et al., 2008; Cavicchioli and Carella, 2007; Cobb et al., 1997; Conine et al., 1990, 1993, 1994; Cooper et al., 1998; Gebhardt et al., 1996; Geyer et al., 2001; Gilcreast et al., 2005; Laurent, 1997; Lim et al., 1988; McGowan et al.,
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2000; Nixon et al., 2006, 1998; Russell and Lichtenstein, 2000; Russell et al., 2003; Schultz et al., 1999; Stapleton, 1986; Summer et al., 1989; Takala et al., 1996; Vyhlidal et al., 1997; Whitney et al., 1984). Thirty-three trials were judged to be free of selective outcome reporting (Andersen et al., 1982; Aronovitch et al., 1999; Cavicchioli and Carella, 2007; Cobb et al., 1997; Collier, 1996; Conine et al., 1993, 1994; Cooper et al., 1998; Daechsel and Conine, 1985; Economides et al., 1995; Ewing et al., 1964; Feuchtinger et al., 2006; Geyer et al., 2001; Goldstone et al., 1982; Laurent, 1997; Lazzara and Buschmann, 1991; Lim et al., 1988; McGowan et al., 2000; Nixon et al., 2006, 1998; Price et al., 1999; Russell and Lichtenstein, 2000; Russell et al., 2003; Sanada et al., 2003; Santy et al., 1994; Schultz et al., 1999; Sideranko et al., 1992; Summer et al., 1989; Takala et al., 1996; Taylor, 1999; Theaker et al., 2005; Tymec et al., 1997; Vyhlidal et al., 1997; Whitney et al., 1984). Thirty-seven trials reported that participant groups under investigation were similar regarding prognostic factors (including age, sex, continence and/or reasons for immobility) (Andersen et al., 1982; Aronovitch et al., 1999; Bennett et al., 1998; Cadue et al., 2008; Conine et al., 1990, 1993, 1994; Cooper et al., 1998; Daechsel and Conine, 1985; Economides et al., 1995; Exton-Smith et al., 1982; Feuchtinger et al., 2006; Gebhardt et al., 1996; Gentilello et al., 1988; Geyer et al., 2001; Goldstone et al., 1982; Gunningberg et al., 2000; Hofman et al., 1994; Inman et al., 1993; Keogh and Dealey, 2001; Laurent, 1997; Lazzara and Buschmann, 1991; Lim et al., 1988; McGowan et al., 2000; Mistiaen et al., 2009; Nixon et al., 2006; Price et al., 1999; Russell and Lichtenstein, 2000; Russell et al., 2003; Sanada et al., 2003; Santy et al., 1994; Schultz et al., 1999; Stapleton, 1986; Takala et al., 1996; Taylor, 1999; Theaker et al., 2005; Vanderwee et al., 2005). Thirteen trials included patients with pre-existing pressure ulcers. Of these, seven included only those with Grade 1 pressure ulcers (Cavicchioli and Carella, 2007; Exton-Smith et al., 1982; Hofman et al., 1994; Keogh and Dealey, 2001; Mistiaen et al., 2009; Nixon et al., 1998; Vanderwee et al., 2005), three included Grades 1 and 2 (Bennett et al., 1998; Nixon et al., 2006; Santy et al., 1994), and one study included only those that were Grade 4 (Economides et al., 1995). For two trials it was not clear what grades of pressure ulcer were included (Feuchtinger et al., 2006; Lazzara and Buschmann, 1991) and for 14 trials it was unclear or unstated whether pre-existing pressure ulcers were included. Trials were classified into those that evaluated ‘lowtech’ devices, ‘high-tech’ devices and other types of support surfaces. This classification system is commonly used, for example in national clinical guidelines (National Institute for Clinical Excellence, 2003). Twenty-three trials evaluated low-tech constant lowpressure support surfaces (foam body supports, sheepskin overlay, heel devices and mattresses). Twenty-one trials evaluated high tech support surfaces (alternating pressure redistribution devices, low-air-loss beds and air fluidised beds). Other support surfaces included kinetic turning tables (two trials), profiling beds (one study), operating table overlays (six trials) and seat cushions (four trials). Characteristics of the included trials and risk of bias assessment of the trials appear in
Tables 1 and 2, respectively. Table 3 shows the results of analyses.
4. Comparisons: ‘low-tech’ constant low pressure support surfaces 4.1. Comparisons between ‘low-tech’ constant low pressure support surfaces and standard foam surfaces Nine trials evaluated a standard foam hospital mattress compared with a ‘low-tech’ constant low pressure support surface, including: water-filled mattresses (Andersen et al., 1982); alternative foam mattresses (Collier, 1996; Gray and Campbell, 1994; Hofman et al., 1994; Russell et al., 2003; Santy et al., 1994); bead beds (Goldstone et al., 1982); visco-elastic mattresses (Gunningberg et al., 2000) and other low-tech mattresses (Takala et al., 1996). The five trials (Collier, 1996; Gray and Campbell, 1994; Hofman et al., 1994; Russell et al., 2003; Santy et al., 1994) comparing foam alternatives with the standard hospital mattress were pooled using a random effects model (I2 = 77%, x2 13.24, df = 3, p = 0.004). This analysis yielded a pooled risk ratio of 0.40 (95% CI 0.21–0.74) or a relative reduction of pressure ulcer incidence of 60% (95% CI 26– 79%), favouring the use of the foam alternative support surfaces. The high heterogeneity in standard hospital mattresses amongst these trials led to a separate metaanalysis of four UK-based trials (Collier, 1996; Gray and Campbell, 1994; Russell et al., 2003; Santy et al., 1994) as variation in the standard hospital mattress is likely to be lower in the UK. This analysis showed a significant benefit of alternative foam over standard foam being maintained (RR 0.41, 95% CI 0.19–0.87). As heterogeneity in this pooled group was high (I2 = 84%, x2 12.41, df = 2, p = 0.002), Russell et al. (2003) was removed as it was an outlier. Heterogeneity was reduced (I2 = 39%) and the pooled results maintained a significant effect in favour of the alternative foam support over the standard support surface (RR 0.29, 95% CI 0.16–0.52). The four remaining trials in this category evaluated a range of products against the standard hospital mattresses. The incidence and severity of pressure ulcers in patients deemed at ‘high risk’ were reduced when patients were placed on either a bead filled mattress (Goldstone et al., 1982) (RR 0.32, 95% CI 0.14–0.76), a water-filled mattress (Andersen et al., 1982) (RR 0.35, 95% CI 0.15–0.79) or a constant low-pressure mattress (Takala et al., 1996) (RR 0.06, 95% 0–0.99). Gunningberg et al. (2000) did not find any significant difference in pressure ulcer incidence for those allocated to a visco-elastic foam trolley mattress (in ED) and standard mattress (on the ward) (4/48, 8%) compared with those assigned to a standard trolley mattress (in ED) and standard mattress (on the ward) (8/53, 15%) (p = 0.36). 4.2. Comparisons between alternative foam support surfaces Three trials (Gray et al., 1998; Kemp et al., 1993; Vyhlidal et al., 1997) compared different foam alternatives
Table 2 Characteristics of included trials. Study (year)
Participants
Grade 1 pressure ulcers included
Intervention (sample size)
Reported follow-up
No
Standard hospital mattress (n = 161) vs. alternating air mattress (n = 166) vs. water filled mattress (n = 155) Foam body support with standard protocol (n = 35) vs. Standard protocol (n = 35) Comparison of 8 foam mattresses (n = 78) Dry flotation mattress (n = 49) vs. dry flotation mattress (n = 51) Sheepskin (n = 18) vs. No sheepskin (n = 18)
10 days
Nod
Collier (1996) Cooper et al. (1998)
Patients from a general medical ward Patients aged > 65 years from mixed emergency and orthopaedic trauma wards Elderly patients confined to bed, with reduced mobility as a result of neurological disorders, fixed joints or peripheral vascular disease Participants from military tertiary academic medical centres, moderate-high risk of pressure ulcer development Patients from orthopaedic trauma, vascular and medical oncology units, with no breaks in the skin. Waterlow score > 15 Patients admitted to a district general hospital, weight < 160 kg Patients aged > 60 years with a femur fracture Patients aged > 65 years with a suspected hip fracture, admitted via A&E
No Nod
Patients with a fractures neck of femur. Dutch consensus risk scale score > 8 Patients aged > 18 years, low – moderate risk of developing a pressure ulcer
Yes
Ewing et al. (1964)
Gilcreast et al. (2005)
Gray and Campbell (1994)
Gray et al. (1998) Goldstone et al. (1982) Gunningberg et al. (2000) c
Hofman et al. (1994) Jolley et al. (2004)
Kemp et al. (1993) Lazzara and Buschmann (1991) McGowan et al. (2000)
Mistiaen et al. (2009) Russell et al. (2003)
Santy et al. (1994) Sideranko et al. (1992) b
Unclear
30 days Unclear 7 days 6 months
No
Heel protector (n = 77) vs. egg crate (n = 86) vs. foot waffle (n = 76)
Unclear
Nod
Mattress (n = 50) vs. standard mattress (n = 50)
10 days
Nod
Foam mattress (n = 50) vs. foam mattress (n = 50)
10 days
Unclear Nod
Bead bed system (n = 32) vs. standard supports (43) Visco-elastic foam mattress (A&E) and visco-elastic foam overlay (ward) (n = 48) vs. standard mattress (A&E) and standard overlay (ward) (n = 53) Cubed foam mattress (n = 21) vs. standard mattress (n = 23) Sheepskin mattress overlay (n = 270) vs. standard care (n = 269)
Unclear 14 days or until discharge
No
Patients aged > 65 from general medical, acute geriatric, long-term care wards. Braden score > 16 Nursing home residents at risk of pressure ulcer development. Norton score > 15 Patients aged > 60 years from an extended care facility, at risk of developing a pressure ulcer, use of a wheelchair 3 h a day. Norton score 14
Nod
Patients from an aged care facility and rehabilitation centre Patients from acute elderly, orthopaedic and rehabilitation units, aged > 60 years
Yes
Patients aged > 55 years with a hip fracture or pressure ulcers Patients from ICU > 48 h
Unclear d
Convoluted foam overlay (n = 45) vs. solid foam overlay (39) Air-filled overlay (n = 33) vs. gel mattress (n = 33)
14 days Mean: 7 days (experimental group), 7.9 days (control group) 1 month 6 months
Standard hospital mattress and sheets, sheepskin overlay, heel and elbow protectors (n = 155) vs. standard hospital mattress and sheets and other low-tech devices as required (n = 142) Sheepskin (n = 271) vs. standard care (n = 272)
Until discharge or transfer
Unclear
Visco-polymer energy absorbing foam mattress and cushion (n = 562) vs. standard mattress and cushion (n = 604)
Yes
Comparison between 4 foam mattresses (n = 441) vs. NHS standard mattress (n = 64) Alternating air overlay (n = 20) vs. Static air mattress (n = 20) vs. Water mattress (n = 17)
Median: 8–14 days (experimental group), 9–17 days (control group) 14 days
No
Nod
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‘Low tech’ constant low pressure support surfaces (n = 23)a Andersen et al. (1982)b Patients from the acute setting at high risk of pressure ulcer development (Anderson Scale) Cadue et al. (2008) Patients from ICU, aged > 18 years. Waterlow score > 10
Unclear
Mean: 9.4 days 351
352
Table 2 (Continued ) Study (year)
Participants
Grade 1 pressure ulcers included
Intervention (sample size)
Reported follow-up
Stapleton (1986) b
Female elderly patients with a fractured neck of femur. Norton score < 14. Patients from ICU with an expected length of stay > 5 days
Nod
Large cell ripple overlay (n = 32) vs. polyether foam pad (n = 34) vs. Silicore fibre overlay (n = 34) Continuous low-pressure mattress (n = 21) vs. standard hospital foam mattress (n = 19) Foot waffle (n = unclear) vs. hospital pillow (n = unclear) Foam overlay (n = 20) vs. fibre mattress replacement (n = 20)
Unclear
Takala et al. (1996) Tymec et al. (1997) Vyhlidal et al. (1997)
Patients from large hospital. Braden score < 16 Newly admitted patients to a skilled nursing facility with an estimated stay 10 days. Braden score < 18
d
No Nod
Yes
Range: 1–60 days 2 weeks
No
Dry flotation mattress (n = 6) vs. air-fluidised bed (n = 6)
2 weeks
Yes
Alternating pressure mattress (n = 31) vs. large cell ripple mattress (n = 31) Alternating pressure supports (overlays/mattresses/beds) (n = 23) vs. constant low pressure supports (overlays/ mattresses/beds) (n = 20) Alternating pressure mattress (n-36) vs. Alternating pressure mattress (n = 39) Low-air-loss beds (n = 49) vs. standard ICU bed (n = 49)
2 weeks
Yes
Nod No
d
Nod
Nod
No details provided
Unclear
Inman et al. (1993)
Patients aged > 17 years, APACHE score > 15. ICU stay > 3 days Patients aged > 55 years with an expected length of hospital stay 7 days. Braden score = 1–2 Patients aged > 15 years and admitted for major cardiovascular surgery. Hospital stay 5 days with an ICU admission
Unclear
Laurent (1997)
Price et al. (1999) Sanada et al. (2003) Taylor (1999)
Theaker et al. (2005)
Patients aged > 60 years with a fractured neck of femur. Medley score > 25 Patients from an acute care unit. Bed bound and requiring head elevations. Braden score 16. Patients aged > 16 years
Patients aged > 80 years from ICU. At high risk of pressure ulcer development
Unclear Range: 10 – 21 days
Low-air-loss hydrotherapy [Clensicair – SSI/Hillrom] (n = 42) vs. standard care (n = 56) High-tech mattress on alternating low-pressure setting (n = 86) vs. high-tech mattress on continuous lowpressure setting (n = 84) [both due 2 – Hill Rom] Low-air-loss bed [KinAir – KCI] (n = 62) vs. Static air mattress overlay [Waffle – EHOB] (n = 61) Alternating pressure overlay(n = 72) vs. Silicore fibre overlay (n = 76) Alternating pressure mattress (n = 16) vs. Silicore fibre overlay (n = 16)
Hampton (1997)
Nixon et al. (2006)
14 days
Yes Unclear
Unclear Nod No
d
Nod
Alternating pressure overlay (n = 990) vs. Alternating pressure mattress (n = 982) Standard mattress (ICU) and standard mattress (post-op) (n = 80) vs. Alternating pressure mattress (ICU) and standard mattress (post-op) (n = 80) vs. standard mattress (ICU) vs. Continuous low-pressure mattress (post-op) (n = 75) vs. Alternating-pressure mattress (ICU) and continuous low-pressure mattress (post-op) (n = 77) Low pressure mattress and cushion (n = 40) vs. alternating pressure mattress and cushion (n = 40) Double layer air cell overlay (n = 37) vs. Single layer air cell overlay (n = 36) vs. standard hospital mattress (n = 35) Alternating pressure mattress with pressure redistributing cushion (n = 22) vs. alternative alternating pressure system with pressure redistributing cushion (n = 22) Alternating pressure bed (n = 30) vs. alternating pressure mattress (n = 32)
40 days 3 months 3 months
Unclear
20 days (maximum) Mean: 17 days 60 days Unclear
14 days Unclear Until discharge
2 weeks post-ICU discharge
E. McInnes et al. / International Journal of Nursing Studies 49 (2012) 345–359
‘High tech’ pressure support surfaces (n = 18)a Bennett et al. (1998) Acute and long term incontinent patients. In bed > 16 h a day Cavicchioli and Carella (2007) Acute and long-term care patients at risk of pressure ulcers and an expected admission 2 weeks. Braden score < 17 or mobility or subscales < 3 respectively Cobb et al. (1997) Patients aged > 18 years from hospital wards and ICU. Expected length of stay 1–2 weeks. Conine et al. (1990) Patients aged 18–55 years with evidence of chronic neurological disease Daechsel and Conine (1985) Patients from a long-term care hospital with chronic neurological conditions and considered at high risk of pressure ulcers Economides et al. (1995) Patients with stage 4 pressure ulcers requiring myocutaneous flap closure Exton-Smith et al. (1982) Newly admitted geriatric patients with a fractured neck of femur Gebhardt et al. (1996) ICU patients with an admission > 3 days. Norton score < 1
Unclear
Vanderwee et al. (2005)
Whitney et al. (1984)
Patients aged > 18 years from surgical, internal medicine or geriatric hospital wards. An expected hospital stay of 3 days. Braden score < 17. Patients from medical-surgical wards in bed for 20 h a day
Gentilello et al. (1988) Geyer et al. (2001)
Keogh and Dealey (2001) Lim et al. (1988) Nixon et al. (1998)
Russell et al. (2000)
Schultz et al. (1999) Summer et al. (1989)
a b c d
Critically ill patients in a surgical ICU, immobilised due to head injury, spinal injuries or traction Patients aged > 65 years, in a wheelchair. Tolerance of sitting in a wheelchair 6 h, weight > 250 lbs. Braden score 18 Patients aged > 18 years, from surgical and medical wards. Waterlow score = 15–25 Patients aged > 60 years from an extended care facility. Use of a wheelchair 3 h/day. Norton score 14 Patients aged > 55 years, admitted for major general, gynaecological or vascular surgery in supine or lithotomy position Patients aged > 18 years, undergoing scheduled cardiothoracic surgery under general anaesthesia and long Patients aged > 18 years, admitted for surgery 2 h in lithotomy position Patients from ICU with sepsis, pneumonia, respiratory failure, drug overdose, metabolic coma, stroke, neuromuscular disease or ARDS
Does not include trials appearing under another subheading. Paper is also considered under ‘low-tech constant low pressure support surfaces’. Paper is also considered under ‘other pressure support surfaces’. Existing pressure ulcers part of exclusion criteria.
Unclear
Nod No
Alternating pressure mattress with air cushion for sitting (n = 222) vs. visco-elastic foam mattress and air cushion for sitting (n = 225) Alternating pressure mattress (n-25) vs. convoluted foam bed (n = 26)
Unclear
Alternating pressure system [MicroPulse] (n = 112) vs. conventional management (n = 105) Slab cushion (n = 144) vs. contoured foam cushion (n = 144)
7 days
8 days
3 months
Unclear
Gel cushion (n = 68) vs. foam cushion (n = 73)
3 months
Unclear
Operating table with water filled warming mattress and thermoactive visco elastic foam overlay (n = 85) vs. operating table with water filled warming mattress (n = 90) Kinetic treatment table (n = 27) vs. conventional bed (n = 38) Pressure reducing cushion (n = 15) vs. standard foam cushion (n = 17)
5 days
Unclear No
Yes
Profiling bed (n = 50) vs. flat-based bed (n = 50)
No
Foam slab cushion (n = 26) vs. contoured foam cushion (n = 26) Dry visco elastic pad (n = 222) vs. standard mattress (n = 224)
Yes
Unclear 12 months
Range: 5 – 10 days 5 months 8 days
Nod
Alternating pressure overlay (n = 98) vs. Conventional care (n = 100)
7 days
Nod
Experimental mattress overlay (n = 206) vs. usual care (n = 207) Kinetic treatment table (n = 43) vs. conventional bed with 2-hourly turning (n = 43)
6 days
Unclear
Unclear
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‘Other’ pressure support surfaces (n = 12)a Aronovitch et al. (1999) Patients aged > 18 years, undergoing surgery (>3 h) under general anaesthesia Conine et al. (1993) Patients aged > 60 years from an extended care facility and high risk of a pressure ulcer. Sitting in a wheelchair for 4 h/day Conine et al. (1994) Elderly patients in an extended care hospital and at high risk of pressure ulcers. Sitting in a wheelchair for 4 h/ day. Norton score < 14. Feuchtinger et al. (2006) Patients aged > 18 years, scheduled for cardiac surgery with extracorporeal circulation
Yes
353
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Table 3 Results of analyses – pressure ulcer incidence. Comparison
Number of trials (authors)
Participants
Risk ratio (95% CI)
p-Value*
‘Low tech’ constant low pressure support surfaces Comparison between low-tech CLP and SFM supports Bead bed system vs. Standard supports Water filled mattress vs. Standard hospital mattress Constant low pressure mattress vs. Standard support
1 (Goldstone et al.) 1 (Andersen et al.) 1 (Takala et al.)
75 316 40
0.32 (0.14, 0.76) 0.35 (0.15, 0.79) 0.06 (0 to 0.99)
– – –
5 (Collier, Gray 94, Hofman, Russell 03, Santy) 4 (Collier, Gray 94, Russell 03, Santy) 3 (Collier. Gray 94. Santy)
2016
0.40 (0.21, 0.74)
p = 0.004
1980
0.41 (0.19, 0.87)
p = 0.020
814
0.29 (0.16, 0.52)
p < 0.0001
1 1 1 1
505 40 84 70
0.36 0.42 0.66 0.16
0.59) 0.96) 1.16) 0.49)
– – – –
1 (Cooper et al.) 1 (Lazzara)
84 66
0.63 (0.16, 2.47) 0.80 (0.24, 2.72)
– –
3 (Jolley, McGowan, Mistaein)
1281
0.48 (0.31, 0.74)
p = 0.0008
3 (Jolley, McGowan, Mistaein)
1281
Fixed effect:
p = 0.04
0.56 (0.32, 0.97) Random effect: 0.60 (0.34, 1.08)
p = 0.09
Pooled trials Foam alternatives vs. Standard hospital mattress Foam alternatives vs. Standard hospital mattress (UK trials only) Foam alternatives vs. Standard hospital mattress (Russell et al., 2002 excluded) Comparisons between AFM supports Standard mattress vs. 4 foam mattresses Fibre mattress replace vs. foam overlay Convoluted foam overlay vs. Solid foam overlay Foam body support (+standard protocol) vs. Standard protocol Comparison between dry flotation mattresses Air filled overlay vs. Gel mattress Pooled trials: Comparison between sheepskins (all pressure ulcer grades) Comparison between sheepskins (pressure ulcers Grade 2 and above)
‘High tech’ pressure support surfaces AP: Comparison between AP and SFM supports Pooled trials: Alternating air-mattress vs. Overlay
(Santy et al.) (Vyhlidal et al.) (Kemp et al.) (Cadue et al.)
(0.22, (0.18, (0.37, (0.05,
2 (Andersen, Sanada)
409
0.31 (0.17, 0.58)
p = 0.0002
4 (Conine 90, Daeschel, Stapleton, Whitney) 3 (Andersen, Sideranko, Price)
31
0.91 (0.72, 1.16)
p = 0.46
458
1.31 (0.51, 3.35)
p = 0.57
10 (Andersen, Cavicchioli, Conine 90, Daeschel, Gebhardt, Price, Sideranko, Stapleton, Vanderwee, Whitney)
1606
0.85 (0.64, 1.13)
p = 0.28
1 (Bennett et al.)
98
2.67 (0.86, 8.27)
–
Pooled trials: Comparison between LAL beds
2 (Inman, Cobb)
221
0.33 (0.16, 0.67)
p = 0.002
Air-fluidised beds Air fluidised bed vs. dry flotation mattress
1 (Economides et al.)
12
1.00 (0.20, 4.95)
–
2 (Gentillelo, Summer)
151
1.23 (0.57, 2.65)
p = 0.59
1 (Feuchtinger et al.)
175
1.53 (0.69, 3.39)
–
1 (Nixon et al., 98)
65
0.53 (0.33, 0.85)
–
2 (Aronovitch, Russell 00)
368
0.21 (0.06, 0.70)
p = 0.01
1 (Conine et al., 93)
248
1.00 (0.84, 1.18)
–
AP: Comparison between AP and CLP supports Pooled trials: Silicore vs. foam overlays Alternating pressure device vs. static water/ air mattresses Alternating pressure devices vs. constant low-pressure support
LAL beds Alternating pressure device vs. static water/ air mattresses
Other pressure supports Kinetic turning tables Pooled trials: Comparison between kinetic turning table and conventional bed Operating table overlays Water filled warming mattress and overlay vs. water filled warming mattress Dry visco-elastic pad vs. standard mattress Pooled trials: Alternating pressure system intraoperatively vs. conventional care Seat cushions Slab cushion vs. contoured foam cushion
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Table 3 (Continued ) Comparison
Number of trials (authors)
Participants
Risk ratio (95% CI)
p-Value*
Seat cushion vs. standard cushion Jay cushion vs. foam cushion
1 (Lim et al.) 1 (Geyer et al.) 1 (Conine et al., 94)
52 32 141
1.06 (0.75, 1.49) 0.68 (0.33, 1.42) 0.61 (0.37, 1.00)
– – –
*
p-values only reported for pooled analyses.
and are reported as individual results below as the evaluated interventions are heterogeneous. Vyhlidal et al. (1997) found a significant reduction in pressure ulcer incidence in people randomised to a fibre mattress replacement when compared with a foam overlay (RR 0.42, 95% CI 0.18–0.96). No significant differences in pressure ulcer incidence rates were found when comparing a convoluted foam overlay and a solid foam overlay (RR 0.66, 95% CI 0.37–1.16) (Kemp et al., 1993) or in comparison of two foam mattresses, Transfoam (one Grade 4 ulcer) and Transfoamwave (one Grade 2 ulcer) (Gray et al., 1998). 4.3. Other ‘low-tech’ support surfaces with various comparisons Three trials evaluating the use of sheepskins compared to standard care were pooled (Jolley et al., 2004; McGowan et al., 2000; Mistiaen et al., 2009). A random effects model was used as heterogeneity was substantial (I2 = 52%, x2 4.20, df = 2, p = 0.12). There were significantly fewer pressure ulcers of any grade amongst those allocated to sheepskins (RR 0.48, 95% CI 0.31–0.74). Across the three trials, out of 1281 participants, 51 ulcers were Grade 2 and higher (3 participants developed an ulcer of Grades 3 or 4) and most ulcers were Grade 1. An analysis examining Grade 2 and higher pressure ulcers yielded significant results (RR 0.56, 95% CI 0.32–0.97) using a fixed effects analysis as (I2 = 3%, x2 2.06, df = 2, p = 0.36). However, a random effects analysis was also undertaken due to the methodological heterogeneity (in terms of the participants and quality of the trials), and this was not significant (RR 0.60, 95% CI 0.34–1.08). A significant reduction in pressure ulcer incidence was found in a study comparing a foam body support with a standard care protocol which included a water mattress, half seated position and massages (RR 0.16, 95% CI 0.05–0.49) (Cadue et al., 2008). A comparison of a heel support surface (foot waffle) with elevation of heels using a hospital pillow, reported the incidence of pressure ulcers in the foot waffle group (n = 6) to be triple that of the comparison group (n = 2) (study group numbers were not specified) (Tymec et al., 1997). Another evaluation of a foot waffle (5/76), egg crate (4/87) and bunny boot (3/77) showed no differences, however, it was not clear whether the results related to the number of ulcers or the number of people with ulcers (Gilcreast et al., 2005). Comparisons of two dry flotation mattresses (Cooper et al., 1998); a gel mattress and an air filled overlay (Lazzara and Buschmann, 1991); alternating air overlay, static air mattress and a water mattress (Sideranko et al., 1992)
and a large cell ripple mattress, polyether foam bed and a Spenco pad (Stapleton, 1986), found no significant differences. 5. Comparisons: ‘high-tech’ pressure support surfaces 5.1. Comparisons between alternating pressure supports and standard hospital mattress Two trials which compared alternative pressure supports compared with a standard hospital mattress (Andersen et al., 1982; Sanada et al., 2003) were pooled using a fixed effect model (I2 = 0%, x2 0.02, df = 1, p = 0.0002). There was a significant reduction in pressure ulcer development favouring the alternating pressure surface (RR 0.31, 95% CI 0.17–0.58). 5.2. Comparisons between alternating pressure supports and constant low pressure supports No significant differences were found between Silicore or foam overlays and alternating pressure devices when pooling four studies (RR 0.91; 95% CI 0.72–1.16) (Conine et al., 1990; Daechsel and Conine, 1985; Stapleton, 1986; Whitney et al., 1984). Nor were significant differences found in a pooled analysis comparing alternating pressure devices and static water or static air mattresses (Andersen et al., 1982; Price et al., 1999; Sideranko et al., 1992) (RR 1.31, 95% CI 0.51–3.35). A pooled random effects analysis of 10 RCT’s comparing various constant low-pressure devices and alternatingpressure devices (Andersen et al., 1982; Cavicchioli and Carella, 2007; Conine et al., 1990; Daechsel and Conine, 1985; Gebhardt et al., 1996; Price et al., 1999; Sideranko et al., 1992; Stapleton, 1986; Vanderwee et al., 2005; Whitney et al., 1984) found no significant difference between the devices (RR 0.85; 95% CI 0.64–1.13). A comparison of various combinations of standard, constant low-pressure and alternating pressure mattresses showed no significant benefits of using alternating pressure in surgical intensive care patients intra- and post-ICU (Laurent, 1997). 5.3. Comparisons between different alternating pressure devices A two-layer large cell ripple alternating pressure device was found to be significantly more effective in preventing pressure ulcers compared with another alternating-pressure device (16% vs. 34%, p > 0.05) (Exton-Smith et al., 1982). No other significant differences were observed in any of the other four trials in this group.
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5.4. Low-air-loss and air-fluidised beds Three trials evaluated the use of low-air-loss beds in preventing pressure ulcers (Bennett et al., 1998; Cobb et al., 1997; Inman et al., 1993). Of these, two that compared low-air-loss beds with a bed and overlay were pooled using random effects (I2 = 26%) (Cobb et al., 1997; Inman et al., 1993). A significant difference in favour of the low-air-loss beds was found (RR 0.33, 95% CI 0.16–0.67). The comparison between low-air-loss hydrotherapy and standard care (Bennett et al., 1998) found that there was a higher pressure ulcer incidence amongst those study participants cared for on a the low-air-loss hydro support surface (19%) compared to those who received standard care (7%) (RR 2.67, 95% CI 0.86–8.27). No significant differences were found between an air-fluidised bed and a dry flotation mattress (Economides et al., 1995). 6. Comparisons between other pressure supports 6.1. Operating table overlays Two trials compared the Micropulse system with a gel pad during surgery and a standard mattress postoperatively (Aronovitch et al., 1999, Russell and Lichtenstein, 2000). These two trials were pooled (fixed effect model I2 = 0%, x2 0.40, df = 1, p = 0.01) and the Micropulse system was found to be significantly better at preventing pressure ulcers (RR 0.21, 95% CI 0.06–0.70). There was a significant reduction in the incidence of post-operative pressure ulcers in participants allocated a dry visco-elastic pad compared to standard care (RR 0.53, 95% CI 0.33–0.85) (Nixon et al., 1998). Schultz et al. (1999) reported a higher incidence of pressure ulcers in patients in the overlay group (26.6%) compared with 16.4% in the standard care group (16.4%). More details about this study was sought from the author but were not forthcoming. The study by Feuchtinger et al. (2006) was terminated because more people in the thermoactive viscoelastic foam overlay group developed pressure ulcers (2 compared to one in the group allocated a water-filled warming mattress without the overlay). 6.2. Kinetic turning tables and profiling beds Using a fixed effect model (I2 = 0%, x2 0.35, df = 1, p = 0.59), there was no evidence of a significant difference between kinetic turning tables compared with conventional beds (Gentilello et al., 1988, Summer et al., 1989) (RR 1.23, 95% CI 0.57–2.65). Keogh et al. reported that no pressure ulcers occurred in those cared for on a profiling bed or on a flat-based bed. 6.3. Seat cushions Four trials (Conine et al., 1993, 1994; Geyer et al., 2001; Lim et al., 1988) evaluated the use of seat cushions. No significant differences were found in the two trials that compared slab and contoured foam cushions (Conine et al., 1993; Lim et al., 1988) (RR 1.00, 95% CI 0.84–1.18) and (RR 1.06, 95% 0.75–1.49). Nor were differences found between
a pressure redistribution seat cushion compared with a standard cushion (Geyer et al., 2001: RR 0.68, 95% CI 0.33– 1.42) or between a Jay cushion and foam cushion (Conine et al., 1994: RR 0.61, 95% CI 0.37–1.00). 7. Discussion This systematic review shows that a range of foambased, low pressure mattresses and overlays, sheepskins, and also some ‘higher-tech’ support surfaces are more effective than either standard hospital mattresses or standard care in preventing pressure ulcers. In terms of operating theatre support surfaces, Nixon et al. (1998) found a gel-filled overlay to be significantly better than a standard operating table. However, in two other trials a gel-filled overlay on the operating table was less effective than an alternating pressure overlay (the Micropulse system) intra- and post-operatively (Aronovitch et al., 1999; Russell and Lichtenstein, 2000). However in these two trials it is not clear whether this is the result of better postoperative pressure relief. Two other trials (Feuchtinger et al., 2006; Schultz et al., 1999) reported post-operative skin changes as a result of different operating theatre overlays. However, the clinical importance of these results is difficult to ascertain in the absence of details from the authors such as pressure ulcer grading and comprehensive descriptions of products evaluated. In addition, it is difficult to separate out the role of postoperative care and concomitant interventions; either of which may have caused the skin changes (mainly found on buttock and coccyx). There are indications that two other interventions may also be harmful. Firstly, Foot Waffle heel elevators were associated with a non-significant trebling in the incidence of pressure ulcers in a small trial (Tymec et al., 1997). In another small trial over double the number of those cared for on a low-air-loss hydro support surface developed pressure ulcers compared to those allocated standard care (Bennett et al., 1998). However, neither of these trials provided clear information to indicate that the groups were similar at baseline in relation to the most important prognostic factors. Despite the number of comparisons and different products evaluated there remain gaps in the knowledge base for which a rational research agenda could be developed. For example, air fluidised therapy as a prevention strategy has only been compared with dry flotation, and low-air-loss only with standard care. The results of meta-analyses of trials of sheepskins are sensitive to the outcome measure selected. When analysis is confined to Grade 2 and higher pressure ulcers, any significant reduction in pressure ulcer incidence associated with sheepskin disappears. The results reported in the three studies are based predominantly on Grades 1 and 2 pressure ulcers, so the effects of sheepskins on preventing more severe ulcers is uncertain. The estimates obtained when analysing only Grade 2 and higher pressure ulcers varied whether using a fixed effects (results significant) or random effects (results not significant) model. While there is some evidence that sheepskin reduced overall ulceration incidence, once we sample the evidence using Grade 2 and
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higher pressure ulcers, the power is reduced and the heterogeneity means that we cannot be fully confident of the results. It can be postulated that the likely mode of action of sheepskin will reduce friction but not pressure and therefore would be likely to impact on the incidence of Grade 2 ulcers but not on more severe pressure damage. Further evaluations are therefore required of medical sheepskins of sufficient power to identify an effect on Grade 2 ulcer incidence versus Grade 3 and higher.
trials should address the deficiencies discussed above while adhering to the CONSORT statement and also collect data on aspects of equipment performance such as reliability.
7.1. Strengths and limitations
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Generally, the risk of bias in the included trials was high. While recent trials have improved reporting of some study details, common methodological flaws included lack of allocation concealment, lack of baseline comparability, high attrition rates, lack of intention to treat analysis, lack of blind or independently verified outcome assessment. Less than half of the trials included sample size estimates and small sample size was a limitation in many. Other flaws include failure to report on pressure ulcer status on study entry. In many trials the definitions of ‘pressure ulcer free’, ‘low-risk’, ‘moderate-risk’ and ‘highrisk’ varied widely and in some trials we were unable to ascertain whether study participants with Grade 1 ulcers were accepted into the sample and included in the analyses. ‘Standard care’ was poorly described in many trials and clear descriptions of interventions were also often lacking. Many of the trials reviewed did not provide information about co-interventions, such as repositioning, and whether these were provided equally to each study arm. In terms of publication bias, it is important to note that many of the published trials identified had received some funding from manufacturers. It is also important for the reader to be aware that in the older trials the materials used in the production of support surfaces may no longer be used. The strengths of our systematic review are the rigorous searching and sifting methods, double data extraction and double assessment of risk of bias using a standardised tool and that we made attempts to contact study authors to obtain additional information when needed. Our findings are also consistent with a systematic review of RCT’s and quasi-randomised trials investigating the prevention of heel pressure ulcers (Junkin and Gray, 2009) a systematic review on general pressure ulcer prevention (Reddy et al., 2006) and a review of three trials investigating the effectiveness of Australian Medical Sheepskins (Mistiaen et al., 2010). 8. Conclusion A range of products such as low pressure mattresses and overlays, sheepskins, and some ‘higher-tech’ support surfaces are effective at preventing pressure ulcers. However, the relative merits of some interventions such as higher-tech constant low pressure and alternating pressure remain unclear. The use of seat cushions has not been adequately evaluated and the findings of some trials are hampered by small sample size and low quality. Future
Conflict of interest None declared. References
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