Key messages
Beds, mattresses and mattress toppers that regularly redistribute pressure under the body may reduce the chance of pressure ulcers developing when compared with surfaces that:
- apply a constant pressure to the skin; and
- are made of foam or gel.
However, they may increase the risk of pressure ulcers developing among nursing home residents when compared with air surfaces that apply constant pressure.
More research is needed to strengthen the evidence that compares air-filled and other surfaces. Future studies should focus on effects that are important to decision-makers, including:
- 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 active, air-filled surfaces:
- prevent pressure ulcers;
- are comfortable and improve people’s quality of life;
- have health benefits that outweigh their costs (cost-effectiveness); 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 an active, air-filled surface. We compared and summarised their results, and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found 32 studies (9058 people, average age: 69 years) that lasted between three and 180 days (average: 14 days). The studies compared active, air-filled surfaces with:
- foam, fibre, water-filled or gel surfaces; and
- other air-filled surfaces.
Pressure ulcer prevention
The evidence suggests that active, air-filled surfaces may reduce the risk of pressure ulcers developing when compared with:
- foam surfaces;
- gel surfaces used on operating tables followed by foam surfaces used on hospitals beds, for people who undergo surgery.
However, active, air-filled surfaces may increase the risk of pressure ulcers developing when compared with reactive air surfaces (1 study, 308 nursing home residents, duration: 14 days).
It is unclear if active air-filled surfaces prevent pressure ulcers compared with surfaces other than reactive foam, gel or air-filled surfaces.
The type of active, air-filled surface used may make little to no difference for preventing pressure ulcers.
Other effects
Active, air-filled surfaces are probably more cost-effective than foam. Mattresses with an active, air-filled surface are probably more cost-effective than mattress toppers with the same surface.
We did not find sufficiently robust and clear evidence to determine how active, air-filled surfaces affect comfort, quality of life and unwanted effects.
What limited our confidence in the evidence?
Most studies were small (83 people on average) and more than two-thirds of them (25) 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 uncertain about the difference in pressure ulcer incidence between using alternating pressure (active) air surfaces and other surfaces (reactive water surfaces, reactive fibre surfaces and reactive air surfaces). Alternating pressure (active) air surfaces may reduce pressure ulcer risk compared with foam surfaces and reactive gel surfaces used on operating tables followed by foam surfaces applied on hospital beds. People using alternating pressure (active) air surfaces may be more likely to develop new pressure ulcers over 14 days' follow-up than those treated with reactive air surfaces in the nursing home setting; but as the result is sensitive to the choice of outcome measure it should be interpreted cautiously. Alternating pressure (active) air surfaces are probably more cost-effective than reactive foam surfaces in preventing new pressure ulcers.
Future studies should include time-to-event outcomes and assessment of adverse events and trial-level cost-effectiveness. Further review using network meta-analysis adds to the findings reported here.
Pressure ulcers (also known as pressure 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. Alternating pressure (active) air surfaces are widely used with the aim of preventing pressure ulcers.
To assess the effects of alternating pressure (active) air surfaces (beds, mattresses or overlays) compared with any 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 alternating pressure (active) air beds, overlays or mattresses. Comparators were any beds, overlays or mattresses.
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.
We included 32 studies (9058 participants) in the review. Most studies were small (median study sample size: 83 participants). The average age of participants ranged from 37.2 to 87.0 years (median: 69.1 years). Participants were largely from acute care settings (including accident and emergency departments). We synthesised data for six comparisons in the review: alternating pressure (active) air surfaces versus: foam surfaces, reactive air surfaces, reactive water surfaces, reactive fibre surfaces, reactive gel surfaces used in the operating room followed by foam surfaces used on the ward bed, and another type of alternating pressure air surface. Of the 32 included studies, 25 (78.1%) presented findings which were considered at high overall risk of bias.
Primary outcome: pressure ulcer incidence
Alternating pressure (active) air surfaces may reduce the proportion of participants developing a new pressure ulcer compared with foam surfaces (risk ratio (RR) 0.63, 95% confidence interval (CI) 0.34 to 1.17; I2 = 63%; 4 studies, 2247 participants; low-certainty evidence). Alternating pressure (active) air surfaces applied on both operating tables and hospital beds may reduce the proportion of people developing a new pressure ulcer compared with reactive gel surfaces used on operating tables followed by foam surfaces applied on hospital beds (RR 0.22, 95% CI 0.06 to 0.76; I2 = 0%; 2 studies, 415 participants; low-certainty evidence).
It is uncertain whether there is a difference in the proportion of people developing new pressure ulcers between alternating pressure (active) air surfaces and the following surfaces, as all these comparisons have very low-certainty evidence: (1) reactive water surfaces; (2) reactive fibre surfaces; and (3) reactive air surfaces.
The comparisons between different types of alternating pressure air surfaces are presented narratively. Overall, all comparisons suggest little to no difference between these surfaces in pressure ulcer incidence (7 studies, 2833 participants; low-certainty evidence).
Included studies have data on time to pressure ulcer incidence for three comparisons. When time to pressure ulcer development is considered using a hazard ratio (HR), it is uncertain whether there is a difference in the risk of developing new pressure ulcers, over 90 days' follow-up, between alternating pressure (active) air surfaces and foam surfaces (HR 0.41, 95% CI 0.10 to 1.64; I2 = 86%; 2 studies, 2105 participants; very low-certainty evidence). For the comparison with reactive air surfaces, there is low-certainty evidence that people treated with alternating pressure (active) air surfaces may have a higher risk of developing an incident pressure ulcer than those treated with reactive air surfaces over 14 days' follow-up (HR 2.25, 95% CI 1.05 to 4.83; 1 study, 308 participants). Neither of the two studies with time to ulcer incidence data suggested a difference in the risk of developing an incident pressure ulcer over 60 days' follow-up between different types of alternating pressure air surfaces.
Secondary outcomes
The included studies have data on (1) support-surface-associated patient comfort for comparisons involving foam surfaces, reactive air surfaces, reactive fibre surfaces and alternating pressure (active) air surfaces; (2) adverse events for comparisons involving foam surfaces, reactive gel surfaces and alternating pressure (active) air surfaces; and (3) health-related quality of life outcomes for the comparison involving foam surfaces. However, all these outcomes and comparisons have low or very low-certainty evidence and it is uncertain whether there are any differences in these outcomes.
Included studies have data on cost effectiveness for two comparisons. Moderate-certainty evidence suggests that alternating pressure (active) air surfaces are probably more cost-effective than foam surfaces (1 study, 2029 participants) and that alternating pressure (active) air mattresses are probably more cost-effective than overlay versions of this technology for people in acute care settings (1 study, 1971 participants).