Beeckman 2019.

Study characteristics
Methods	Study objective: to compare the effectiveness and cost of static air support surfaces versus alternating air pressure support surfaces in a nursing home population at high risk for pressure ulcers Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 14 days Number of arms: 2 Single centre or multi‐site: multi‐site Study start date and end date: April 2017 to May 2018 Setting: nursing home
Participants	Baseline characteristics Inclusion criteria: (1) high risk of developing pressure ulcer (Braden score 12 and/or Braden subscale score for mobility 2) and/or pressure ulcer category 1; (2) being bed bound (> 8 hours in bed) and/or chair bound (> 8 hours sitting in a chair); (3) aged > 65 years; and (4) use of an alternating air pressure mattress Exclusion criteria: (1) nursing home residents with a pressure ulcer category II–IV upon admission; (2) those with an expected length of stay < 2 weeks; (3) those who received end‐of‐life care; or (4) those with medical contraindications for the use of static air support devices Sex (M:F): 71:237 overall; 39:115 in static air support surfaces; 32:122 in alternating air pressure surfaces Age (years): mean 87 (SD 7.6) overall; 86.9 (7.9) in static air support surfaces; 86.8 (7.3) in alternating air pressure surfaces Baseline skin status: mean Braden score 13 (SD 2.2) overall; all at risk according to the risk score used by the authors Group difference: no difference between groups Total number of participants: n = 308 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Static air support surfaces Description of interventions: provided with the static air support surfaces (Repose) ... Repose mattress overlay, Repose1 cushion and Repose1 wedge, or Repose1 foot protector (Frontier Medical Group, South Wales, the UK) ... consist of two urethane multidirectional stretch membranes. The inner membrane is inflated and provides static pressure redistribution throughout the tubular open cells that are oriented along the length of the device. The second membrane is formed from a multidirectional stretch, vapour‐permeable material. NPUAP S3I classification: non‐powered, reactive air surface Co‐interventions: static air‐filled cushion used in 81% of participants and usual seat cushion used in the remaining 19%, static air‐filled foot protectors or wedges used in 100% of participants Number of participants randomised: n = 154 Number of participants analysed: n = 154 Alternating air pressure support surfaces Description of interventions: all using alternating air pressure support surfaces, with a 3 to 30 minute cycle time. However, the surfaces were not standardised to reflect current clinical practice. NPUAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: seat cushions used in 88% and heel protectors used in 34% Number of participants randomised: n = 154 Number of participants analysed: n = 154
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 14 days Reporting: fully reported Measurement method (e.g. scale, self‐reporting): graded using the International Pressure Ulcer Classification system (National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel and, P.P.P.I.A., 2014). Definition (including ulcer stage): cumulative incidence and incidence density of the participants developing a new category II‐IV pressure ulcer within a 14‐day observation period; that is the percentage of participants in the population at risk who developed a new pressure ulcer. Dropouts: intention‐to‐treat (ITT) analysis Notes (e.g. other results reported): 8 of 154 developing category II‐IV pressure ulcer in static air support surfaces (6 category II; 2 category III); 18 of 154 in alternating air pressure support surfaces (15 category II; 1 category III; 2 category IV); (Chi2 test P = 0.04). Ulcer incidence by areas reported also in the paper but not extracted for this review. Category II‐IV ulcer incidence density 0.41/100 observed days (8 ulcers/1970 observed days) (95% CI 0.19 to 0.77) in static air surfaces; 0.89/100 observed days (18 ulcers/2013 observed days) (95% CI 0.55 to 1.39) in alternating pressure air surfaces Time to pressure ulcer development Outcome type: binary Time points: 14 days Reporting: fully reported Measurement method (e.g. scale, self‐reporting): graded using the International Pressure Ulcer Classification system (National Pressure Ulcer Advisory Panel, European Pressure Ulcer Advisory Panel and, P.P.P.I.A., 2014). Definition (including ulcer stage): median time to develop a new ulcer Dropouts: median time to develop an ulcer 10.5 days (interquartile range (IQR) 1 to 14) in static air support surfaces; 5.4 (1 to 12) in alternating air pressure support surfaces (Mann‐Whitney U test P = 0.05); probability to remain pressure ulcer‐free differed between groups (log‐rank X = 4.051, df = 1, P = 0.04); Kaplan–Meier survival plot presented in Fig 2. ln(HR) 0.81 and seln(HR) 0.39 estimated by the review authors using the methods in Tierney 2007. Support‐surface‐associated patient comfort Reporting: not reported All reported adverse events using allocated support surfaces Reporting: not reported Health‐related quality of life (HRQOL) Reporting: not reported Cost‐effectiveness Reporting: not reported Notes: purchase costs of the support surfaces calculated per participant per day given the 2‐year lifespan for a static air mattress and 7‐year lifespan for an alternating air pressure mattresses. The average lifespan of 2 years for a static air mattress resulted in a daily cost of 0.20 euro; the average lifespan of 7 years for an alternating air pressure mattress resulted in a daily cost of 0.53 euro.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The random allocation sequence was based on a computer‐generated list of random numbers using an online tool (www.randomization.com)." Comment: low risk of bias because of the use of a proper randomisation method.
Allocation concealment (selection bias)	Unclear risk	Quote: "When the participants met the inclusion criteria and an informed consent was obtained, they received an allocation number (first available number on the computer‐generated list)." Quote: "Subsequently, a random allocation of each eligible participant was performed based on a computer‐generated list of random numbers." Comment: unclear risk of bias because the process of allocation is not clear for judging if concealment was properly performed and it is unclear who performed allocation.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Outcome group: all outcomes Quote: "The study was not blinded due to the obvious visible difference between the support surfaces (e.g. external control unit)." Comment: high risk of bias because of the understandable challenge of performing blinding.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome group: all outcomes Quote: "The study was not blinded due to the obvious visible difference between the support surfaces (e.g. external control unit). Both support surface types were presented to ward nurses ..." Quote: "During the follow‐up period (days 1–14), the ward nurses collected all data" Quote: "Researchers performed independent and unannounced skin assessments and technical controls weekly" Comment: high risk of bias because of the understandable challenge of performing blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "An intention‐to‐treat analysis was performed." Comment: low risk of bias.
Selective reporting (reporting bias)	Low risk	Comment: the study protocol is available and it is clear that the published reports include all outcomes, including those that were pre‐specified.
Other bias	Low risk	Comment: the study appears to be free of other sources of bias.