Gray 2000.

Study characteristics
Methods	Study objective: to evaluate the ability of 2 pressure‐reducing mattresses to prevent pressure sores in a population who were deemed to be at high risk of sore development. Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 10 days Number of arms: 2 Single centre or multi‐sites: single centre Study start date and end date: not described Setting: acute care settings of a hospital
Participants	Baseline characteristics Inclusion criteria: patients admitted to a district general hospital (either emergency or planned admission) for bed‐rest or surgery, with intact skin, no other skin abnormalities, no terminal illness, weight < 160 kg Exclusion criteria: not given Sex (M:F): 30:20 in Transfoamwave; 31:19 in Transfoam Age (years): mean 69 (SD 4.5) in Transfoamwave; 61 (4.1) in Transfoam Baseline skin status: mean Waterlow 13 (SD 2.5) in Transfoamwave; Waterlow 14 (3.6) in Transfoam; no existing ulcers Group difference: no difference Total number of participants: n = 100 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Transfoam Description of interventions: constructed using foams of varying densities, with uncut surfaces (Gray 2000); "in the viscoelastic foam mattress there is a base layer of robust polyurethane ... " from Beldon 2002. NPIAP S3I classification: non‐powered, reactive foam surface; high‐specification foam Co‐interventions: not described Number of participants randomised: n = 50 Number of participants analysed: n = 50 Transfoamwave Description of interventions: constructed using foams of varying densities, with uncut surfaces NPIAP S3I classification: non‐powered, reactive foam surface; high‐specification foam Co‐interventions: not described Number of participants randomised: n = 50 Number of participants analysed: n = 50
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 10 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): graded using the Torrance scale Definition (including ulcer stage): pressure ulcer incidence of any stages Dropouts: not reported Notes (e.g. other results reported): 1 participant with Grade 2 in Transfoamwave; 1 with Grade 4 in Transfoam. Additionally, 1 participant in each group having non‐blanching erythema Time to pressure ulcer incidence Reporting: not reported Support‐surface‐associated patient comfort Outcome type: categorical Time points: not described Reporting: partially reported Measurement method (e.g. scale, self‐reporting): comfort ratings, on a 5 point scale from ‘very uncomfortable’ to ‘very comfortable' Definition: not reported Dropouts: 2 of 50 in Transfoam and 3 of 50 in Transfoamwave missed Notes: very uncomfortable 0/ uncomfortable 0/ adequate 3/ comfortable 26/ very comfortable 18 of 47 in Transfoamwave; 0/1/2/34/11 of 48 in Transfoam 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)	Unclear risk	Quote: "Individuals who met the entry criteria were randomised to a control or trial mattress using an opaque envelope" Comment: unclear if a proper randomisation method was applied.
Allocation concealment (selection bias)	Unclear risk	Quote: "Individuals who met the entry criteria were randomised to a control or trial mattress using an opaque envelope" Comment: unclear if allocation was concealed.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Outcome group: all outcomes Comment: no information provided.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome group: pressure ulcer outcome Quote: "Tissue damage was assessed by staff who were unaware which mattress the subject was using" Comment: low risk of bias because blinded outcome assessors were used for the comparison of 2 foam mattresses. This blinding is feasible. Outcome group: comfort outcome Comment: high risk of bias because it is unlikely that it was possible to blind patient self‐reported outcome assessment.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Outcome group: pressure ulcer outcome Comment: unclear risk of bias because the number of individuals with data observed was not specified. Outcome group: comfort outcome Comment: low risk of bias because in total 5 of 100 missed.
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.