Ozyurek 2015.

Study characteristics
Methods	Study objective: to compare whether differences exist between 2 viscoelastic foam support surfaces in the development of new pressure ulcers Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: not specified; length of stay 17.36 days (SD 17.9) Number of arms: 2 Single centre or multi‐sites: single centre Study start date and end date: October 2008 and January 2010 Setting: medical and surgical intensive care units of a hospital
Participants	Baseline characteristics Inclusion criteria: patients older than 18 years whose expected length of stay was at least 7 days Exclusion criteria: those with a pressure ulcer (PU) of stage 1 or worse on admission or weighed more than 140 kg or less than 45 kg (as per mattress recommendations); those with Braden score higher than 18 (no risk) Sex (M:F): 26:27 in foam 1; 29:23 in foam 2 Age (years): 64.99 (15.10) across groups; mean 64.77 (SD 15.09) in foam 1; 65.21 (15.26) in foam 2 Baseline skin status: mean Braden score 14.11 (SD 3.35) in foam 1; 13.06 (2.79) in foam 2 Group difference: no difference Total number of participants: 357 randomised; 105 analysed Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Viscoelastic foam 1 Description of interventions: viscoelastic polyurethane foam 1, composed of 2 layers, a 7 cm support surface with 8 cm of high‐flexibility foam NPIAP S3I classification: non‐powered, reactive foam surface; multi‐layered, viscoelastic polyurethane, high‐flexibility foam Co‐interventions: repositioning, nutrition support Number of participants randomised: n = 178 Number of participants analysed: n = 53 Viscoelastic foam 2 Description of interventions: a breathable, open‐cell type of viscoelastic foam, was composed of 3 layers, the top active viscoelastic layer, lower support layer, and side safety barrier NPIAP S3I classification: non‐powered, reactive foam surface; multi‐layered, viscoelastic foam Co‐interventions: repositioning, nutrition support Number of participants randomised: n = 179 Number of participants analysed: n = 52
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: mean length of stay 17 days Reporting: fully reported Measurement method (e.g. scale, self‐reporting): classified pressure ulcers according to the EPUAP classification system Definition (including ulcer stage): number of patients who developed a new pressure ulcer of stage 1 or worse (overall, and by stages) Dropouts: 125 in foam 1 and 127 in foam 2 missed Notes (e.g. other results reported): 22 of 53 in foam 1 (including 12 Stage 1; 9 Stage 2; 1 Stage 3); 23 of 52 in foam 2 (including 16 Stage 1; 7 Stage 2; 0 Stage 3) Time to pressure ulcer incidence Reporting: partially reported Notes: this outcome is not systematically measured. "For patients who developed PUs, the median time to development of the first PU was 4 days and ranged from 1 to 15 days" 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
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was performed through an independent, secure, 24‐hour randomization automated telephone system, ensuring allocation concealment. We used minimization so that groups were parallel" Comment: low risk of bias due to the use of a proper randomisation method.
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was performed through an independent, secure, 24‐hour randomization automated telephone system, ensuring allocation concealment" Comment: low risk of bias due to the proper concealment.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Outcome group: primary outcome Comment: no information provided.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome group: primary outcome Quote: "Skin follow‐up evaluations were completed daily" Comment: no information provided.
Incomplete outcome data (attrition bias) All outcomes	High risk	Outcome group: all Comment: high risk of bias because "FIGURE. Flow of patients through the trial" shows that of 357 individuals who were randomised, only 105 are included in analysis
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.