Bueno de Camargo 2018.

Study characteristics
Methods	Study objective: to analyse whether a viscoelastic mattress support surface can reduce the incidence of stage 2 pressure injuries compared to a standard hospital mattress with pyramidal overlay in critically ill patients Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: not described; followed until intensive care unit (ICU) discharge; median length of ICU stay 11.5 days (interquartile range (IQR) 7.5 to 22) Number of arms: 2 Single centre or multi‐sites: single centre Study start date and end date: 2016 to 2017 Setting: ICU
Participants	Baseline characteristics Inclusion criteria: critically ill patients at moderate or higher risk for development of pressure injuries; that is, those presenting a Braden ≤ 14 scale (moderate, high or very high risk) at ICU admission Exclusion criteria: age less than 18 years, length of stay in the ICU for less than 24 hours, contraindication for the performance of the standard pressure injuries prevention measures of the institution, presence of pressure injuries at ICU admission, and absence of the informed consent form Sex (M:F): 33:29 overall Age (years): mean 67.9 (SD 18.8) overall; 71.5 (18.0) in pyramidal overlay; 64.2 (19.2) in viscoelastic foam Baseline skin status: mean Braden score 10.8 (SD 1.7) overall; all at risk but no existing ulcers Group difference: not described Total number of participants: n = 62 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Viscoelastic mattress Description of interventions: Viscoelastic foam is a type of porous polymer material that conforms in proportion to the applied weight ... used a viscoelastic mattress as a bedding surface with the following characteristics: 5‐centimetre layer of cold foam with a density of 40, and 7‐centimetre layer of viscoelastic foam with a density of 60 (Sweet Pedic Hospitalar®) measuring 190 by 90 centimetres NPIAP S3I classification: non‐powered, reactive foam surface; high specification (viscoelastic) foam (density of 40 and 60) Co‐interventions: institution’s pressure injuries prevention measures Number of participants randomised: n = 31 Number of participants analysed: n = 31 Standard mattress with pyramidal overlay Description of interventions: used a standard hospital mattress covered with a pyramidal overlay. The standard hospital mattress is a 12‐centimetre cold foam with a density of 33 measuring 188 by 80 centimetres. The pyramidal overlay is a 5‐centimetre layer of polyurethane foam, density 33, whose surface looks like egg carton. NPIAP S3I classification: non‐powered, reactive foam surface; foam (density of 33) Co‐interventions: institution’s pressure injuries prevention measures Number of participants randomised: n = 31 Number of participants analysed: n = 31
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: on average of 30 days (NCT02844166) Reporting: partially reported Measurement method (e.g. scale, self‐reporting): not described; the definition appears to be equivalent to NPUAP system Definition (including ulcer stage): incidence of stage 2 pressure injuries: partial‐thickness loss of skin with exposed dermis Dropouts: intention‐to‐treat (ITT) analysis Notes (e.g. other results reported): ulcers occurred in 35 patients; higher in pyramidal overlay (25 of 31; 80.6%) compared to viscoelastic foam mattress (10 of 31; 32.2%) P < 0.001 Time to pressure ulcer incidence Outcome type: time‐to‐event Time points: on average 30 days (NCT02844166) Reporting: fully reported Measurement method (e.g. scale, self‐reporting): not described Definition (including ulcer stage): time from intensive care unit admission to identification of class II pressure injury Dropouts: median time to develop an ulcer 8.5 days (interquartile range (IQR) 5.0 to 14.0) in viscoelastic mattress; 6.0 days (IQR 3.0 to 8.0) in pyramidal overlay; Mann‐Whitney test P = 0.088; Kaplan–Meier curve presented in Figure 2. HR 0.33 (95% CI 0.17 to 0.64), estimated by the review authors using the methods described 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 Outcomes that are not considered in this review but reported in trials: Mortality rate (mentioned in NCT02844166 but not reported in the study's paper).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was performed using a computerized table, and patients were allocated into two groups" Comment: low risk of bias because a proper randomisation method used.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Outcome group: pressure ulcer incidence Quote: "the blinding of the health team was not possible" Comment: high risk of bias as the authors stated no blinding.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome group: pressure ulcer incidence Quote: "the blinding of the health team was not possible" Comment: high risk of bias as the authors stated no blinding.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome group: pressure ulcer incidence Comment: low risk of bias because the paper clearly states ITT analysis performed.
Selective reporting (reporting bias)	High risk	Comment: high risk of bias because even though the study protocol is available but it is clear that the published report does not include mortality outcome that was pre‐specified.
Other bias	Low risk	Comment: the study appears to be free of other sources of bias.