Sauvage 2017.

Study characteristics
Methods	Study objective: to compare Axtair One, an alternating pressure air mattress (APAM), with a viscoelastic foam mattress (VFM) in elderly patients at moderate to high risk of developing pressure ulcers (PUs) Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 30 days Number of arms: 2 Single centre or multi‐sites: multi‐sites Study start date and end date: February 2012 to March 2015 Setting: medium‐ and long‐term stay facilities
Participants	Baseline characteristics Inclusion criteria: males and females aged 70 and over, bedridden for at least 15 hours per day, with reduced mobility due to medical problems (such as malnutrition, low blood pressure, urinary incontinence, neurological diseases and sensory disorders), a low to zero positioning capability, a Karnofsky score ≤ 40% and a planned period of hospitalisation of at least 2 weeks. Had no PUs at the time of enrolment but had a medium to high risk for developing PUs, as defined by a Braden score ≤ 14. Exclusion criteria: a weight > 120kg, body mass index (BMI) < 12kg/m2, a nutritional status score < 12 according to the Mini Nutritional Assessment (MNA), uncompensated nutritional insufficiency and ongoing participation, or within 15 days before, in another clinical research study Sex (M:F): 13:26 in APAM; 9:28 in VFM Age (years): mean 86.03 (SD 5.49) in APAM, 84.59 (6.68) in VFM Baseline skin status: mean Braden score 11.77 (SD 1.27) in APAM, 12.08 (1.26) in VFM; all intact skin Group difference: no difference Total number of participants: n = 76 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Alternating pressure air mattress (APAM) Description of interventions: APAM (Axtair One, Asklé Santé, Nîmes, France) consisted of therapeutic air cells with a height of 12 cm, supplied by a compressor, which adjusts the pressure based on the patient’s weight and whose mode of operation allows alternating inflation of 1 out of 2 cells, with a 6 minute cycle time. NPIAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: not reported Number of participants randomised: n = 39 Number of participants analysed: n = 39 Viscoelastic foam mattress (VFM) Description of interventions: VFM (ALOVA mattress, Asklé Santé, Nîmes, France) was composed of a base made of high resilience foam (density > 34 kg/m3) and an upper layer of viscoelastic foam (density > 75kg/m3). NPIAP S3I classification: non‐powered, reactive foam surface; high specification foam (2 layered; base layer of high resilience foam, density > 34kg/m3; upper layer of viscoelastic foam, density > 75kg/m3). Co‐interventions: not reported Number of participants randomised: n = 37 Number of participants analysed: n = 37
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 30 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): not reported Definition (including ulcer stage): incidence of pressure ulcers of any stage Dropouts: intention‐to‐treat (ITT) analysis performed Notes (e.g. other results reported): 2 of 39 participants in APAM (1 category I ulcer and 1 category II ulcer); 13 of 37 participants in VFM (7 category I ulcers, 5 category II ulcers and 1 category III ulcer). Time to pressure ulcer incidence Outcome type: binary Time points: 30 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): not reported Definition (including ulcer stage): time to appearance of ulcers Dropouts: censoring Notes (e.g. other results reported): the cumulative risk of PUs was estimated at 6.46% (95% confidence interval (CI) 1.64 to 23.66) in the APAM group and at 38.91% (95% CI 24.66 to 57.59) in the VFM group, P = 0.001 (logrank test). Kaplan‐Meier curves presented in Fig 2 and HR 0.18 (95% CI 0.07 to 0.50) estimated by the review authors by using methods described in Tierney 2007. Support‐surface‐associated patient comfort Outcome type: binary Time points: day 8, day 15, day 22, and day 30 Reporting: fully reported Measurement method (e.g. scale, self‐reporting): perception of patient comfort collected on days 8, 15, 22 and 30 via a satisfaction questionnaire (skin‐mattress contact, feeling of warmth, discomfort due to motor noise and disturbed sleep) Definition (including ulcer stage): comfort rates Dropouts: 3 of 39 APAM vs 6 of 37 VFM at day 8 ; 6 of 39 APAM vs 10 of 37 VFM at day 15 ; 11 of 39 vs 16 of 37 at day 22 ; 15 of 39 APAM vs 20 of 37 VFM at day 30. Notes: data presented by subscales of the measurement tool and not extracted for this review. Difference in satisfaction between the 2 groups not significant, P = 0.21 All reported adverse events using allocated support surfaces Notes: the serious adverse events (SAEs) reported in the APAM group were 2 deaths, a massive septic shock with acute pulmonary oedema and a decompensation of an insulin‐dependent diabetes. No SAE was reported in the VFM group. There were 20 adverse events reported in each group, including 2 discomforts in the APAM group and one hyperalgesia in the VFM group. The other events did not involve the mattresses. Health‐related quality of life (HRQOL) Reporting: not reported Cost‐effectiveness Reporting: not reported Outcomes that are not considered in this review but reported in trials: The duration of bed rest The duration of sitting in a chair The frequency of preventative interventions Any therapeutic change
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomisation was centralised (RANDLIST software v1.2) and globally balanced intracentre with random block sizes established from two possibilities (2 and 4)" Comment: low risk of bias because of the use of a proper randomisation method.
Allocation concealment (selection bias)	Unclear risk	Quote: "Randomisation was centralised (RANDLIST software v1.2) and globally balanced intracentre with random block sizes established from two possibilities (2 and 4)" Comment: unclear risk of bias because even though central randomisation was performed, the small block size means that the allocation in the subsequent block is predictable if a prior randomisation sequence has already been known.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Quote: "This randomised, controlled, superiority, parallel‐group, open‐label, multicentre ..." Quote: "PUs preventive care had to be performed in compliance with validated care protocols compliant with Good Professional Practice Recommendations" Comment: high risk of bias because open label is clearly stated. Additionally, it is unknown if performance between groups might be unbiased even though there seems to be a standardised care plan.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Quote: "This randomised, controlled, superiority, parallel‐group, open‐label, multicentre ..." Comment: high risk of bias because open label is clearly stated.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "The population selected for the main analysis were all randomised patients in intention‐to‐treat (ITT)." Comment: low risk of bias because ITT analysis was performed.
Selective reporting (reporting bias)	Low risk	Comment: the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified.
Other bias	Low risk	Comment: the study appears to be free of other sources of bias.