Key messages
Due to a lack of robust evidence, it is unclear whether most types of surface that apply constant pressure to the skin and are not air-filled or made of foam prevent pressure ulcers.
Lying surgery patients on an operating table with a gel surface that applies constant pressure to the skin and then a hospital bed with a foam surface, rather than using air-filled surfaces, may increase the risk of developing pressure ulcers.
Future studies should focus on options and effects that are important to decision-makers, such as:
- gel surfaces that apply constant pressure to the skin, compared to air-filled or foam surfaces; and
- whether and when pressure ulcers develop, unwanted effects and costs.
What are pressure ulcers?
Pressure ulcers are also known as pressure sores or bed sores. They are wounds to the skin and underlying tissue caused by prolonged pressure or rubbing. They often occur on bony parts of the body, such as heels, elbows, hips and the bottom of the spine. People who have mobility problems or who lie in bed for long periods are at risk of developing pressure ulcers.
What did we want to find out?
There are beds, mattresses and mattress toppers specifically designed for people at risk of pressure ulcers. These can be made of a range of materials (such as foam, air cells or water bags) and are divided into two groups:
- reactive (static) surfaces that apply a constant pressure to the skin, unless a person moves or is repositioned; and
- active (alternating pressure) surfaces that regularly redistribute the pressure under the body.
We wanted to find out if reactive surfaces that are not air-filled or made of foam:
- prevent pressure ulcers;
- are comfortable and improve people’s quality of life;
- have health benefits that outweigh their costs; and
- have any unwanted effects.
What did we do?
We searched the medical literature for studies that evaluated the effects of beds, mattresses and mattress toppers with a reactive surface that was not air-filled or made of foam. We compared and summarised the results of these studies, and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found 20 studies (4653 people, average age: 73 years) that lasted between seven days and six months (average: four weeks). The studies compared reactive surfaces filled with water or gel, or made of fibre, against other active or reactive surfaces.
In general, the studies did not provide sufficiently robust evidence for us to determine if reactive surfaces that are not air-filled or made of foam prevent pressure ulcers.
Evidence from two studies suggests that people who undergo surgery may be more likely to develop pressure ulcers when they lie on an operating table with a reactive gel surface and then a hospital bed with a foam surface, rather than on active air-filled surfaces.
The other benefits and risks of gel and other reactive surfaces are unclear. No studies reported information about quality of life and cost.
What limited our confidence in the evidence?
Most studies were small (198 people on average) and used methods likely to introduce errors in their results.
How up-to-date is this review?
The evidence in this Cochrane Review is current to November 2019.
Current evidence is generally uncertain about the differences between non-foam and non-air-filled reactive surfaces and other surfaces in terms of pressure ulcer incidence, patient comfort, adverse effects, health-related quality of life and cost-effectiveness. Reactive gel surfaces used on operating tables followed by foam surfaces applied on hospital beds may increase the risk of having new pressure ulcers compared with alternating pressure (active) air surfaces applied on both operating tables and hospital beds.
Future research in this area should consider evaluation of the most important support surfaces from the perspective of decision-makers. Time-to-event outcomes, careful assessment of adverse events and trial-level cost-effectiveness evaluation should be considered in future studies. Trials should be designed to minimise the risk of detection bias; for example, by using digital photography and adjudicators of the photographs being blinded to group allocation. Further review using network meta-analysis adds to the findings reported here.
Pressure ulcers (also known as injuries, pressure sores, decubitus ulcers and bed sores) are localised injuries to the skin or underlying soft tissue, or both, caused by unrelieved pressure, shear or friction. Reactive surfaces that are not made of foam or air cells can be used for preventing pressure ulcers.
To assess the effects of non-foam and non-air-filled reactive beds, mattresses or overlays compared with any other support surface on the incidence of pressure ulcers in any population in any setting.
In November 2019, we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication or study setting.
We included randomised controlled trials that allocated participants of any age to non-foam or non-air-filled reactive beds, overlays or mattresses. Comparators were any beds, overlays or mattresses used.
At least two review authors independently assessed studies using predetermined inclusion criteria. We carried out data extraction, 'Risk of bias' assessment using the Cochrane 'Risk of bias' tool, and the certainty of the evidence assessment according to Grading of Recommendations, Assessment, Development and Evaluations methodology. If a non-foam or non-air-filled surface was compared with surfaces that were not clearly specified, then the included study was recorded and described but not considered further in any data analyses.
We included 20 studies (4653 participants) in this review. Most studies were small (median study sample size: 198 participants). The average participant age ranged from 37.2 to 85.4 years (median: 72.5 years). Participants were recruited from a wide range of care settings but were mainly from acute care settings. Almost all studies were conducted in Europe and America. Of the 20 studies, 11 (2826 participants) included surfaces that were not well described and therefore could not be fully classified. We synthesised data for the following 12 comparisons: (1) reactive water surfaces versus alternating pressure (active) air surfaces (three studies with 414 participants), (2) reactive water surfaces versus foam surfaces (one study with 117 participants), (3) reactive water surfaces versus reactive air surfaces (one study with 37 participants), (4) reactive water surfaces versus reactive fibre surfaces (one study with 87 participants), (5) reactive fibre surfaces versus alternating pressure (active) air surfaces (four studies with 384 participants), (6) reactive fibre surfaces versus foam surfaces (two studies with 228 participants), (7) reactive gel surfaces on operating tables followed by foam surfaces on ward beds versus alternating pressure (active) air surfaces on operating tables and subsequently on ward beds (two studies with 415 participants), (8) reactive gel surfaces versus reactive air surfaces (one study with 74 participants), (9) reactive gel surfaces versus foam surfaces (one study with 135 participants), (10) reactive gel surfaces versus reactive gel surfaces (one study with 113 participants), (11) reactive foam and gel surfaces versus reactive gel surfaces (one study with 166 participants) and (12) reactive foam and gel surfaces versus foam surfaces (one study with 91 participants). Of the 20 studies, 16 (80%) presented findings which were considered to be at high overall risk of bias.
Primary outcome: Pressure ulcer incidence
We did not find analysable data for two comparisons: reactive water surfaces versus foam surfaces, and reactive water surfaces versus reactive fibre surfaces. Reactive gel surfaces used on operating tables followed by foam surfaces applied on hospital beds (14/205 (6.8%)) may increase the proportion of people developing a new pressure ulcer compared with alternating pressure (active) air surfaces applied on both operating tables and hospital beds (3/210 (1.4%) (risk ratio 4.53, 95% confidence interval 1.31 to 15.65; 2 studies, 415 participants; I2 = 0%; low-certainty evidence). For all other comparisons, it is uncertain whether there is a difference in the proportion of participants developing new pressure ulcers as all data were of very low certainty.
Included studies did not report time to pressure ulcer incidence for any comparison in this review.
Secondary outcomes
Support-surface-associated patient comfort: the included studies provide data on this outcome for one comparison. It is uncertain if there is a difference in patient comfort between alternating pressure (active) air surfaces and reactive fibre surfaces (one study with 187 participants; very low-certainty evidence).
All reported adverse events: there is evidence on this outcome for one comparison. It is uncertain if there is a difference in adverse events between reactive gel surfaces followed by foam surfaces and alternating pressure (active) air surfaces applied on both operating tables and hospital beds (one study with 198 participants; very low-certainty evidence).
We did not find any health-related quality of life or cost-effectiveness evidence for any comparison in this review.