Feuchtinger 2006.

Study characteristics
Methods	Study objective: to assess the effect of a 4 cm thermoactive viscoelastic foam overlay with a water‐filled warming mattress on the operating room‐table compared with the standard operating room‐table (a water‐filled warming mattress, no pressure‐reducing device) on the postoperative pressure ulcer incidence in cardiac surgery patients. Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 5 days Number of arms: 2 Single centre or multi‐sites: single centre Study start date and end date: January to June 2004 Setting: Department for Cardiovascular Surgery of a university hospital
Participants	Baseline characteristics Inclusion criteria: scheduled for cardiac surgery with extracorporal circulation, aged ≥ 18 years, not included in another study, and written informed consent obtained Exclusion criteria: not described Sex (M:F): 58: 27 in test table; 67: 23 in standard table Age (years): mean 68 (SD 11) in test table; 67.6 (10.8) in standard table Baseline skin status: mean Norton score 22.6 (SD 1.9) in test table; 22.2 (2.4) in standard table Group difference: no difference Total number of participants: n = 175 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Test operating room table Description of interventions: a 4 cm thermoactive viscoelastic foam pad combined with a warming mattress on the operating table NPIAP S3I classification: non‐powered, reactive foam surface; 4 cm viscoelastic foam operating table pad Co‐interventions: not described Number of participants randomised: n = 85 Number of participants analysed: n = 85 Standard operating room table Description of interventions: a warming mattress on the operating table, no pressure‐reducing device NPIAP S3I classification: standard hospital surface; standard operating table Co‐interventions: not described Number of participants randomised: n = 90 Number of participants analysed: n = 90
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: post‐operative 5 days Reporting: fully reported Measurement method (e.g. scale, self‐reporting): measured by nurses using the EPUAP 2005 classification system Definition (including ulcer stage): postoperative pressure ulcer incidence of any grade Dropouts: intention‐to‐treat (ITT) analysis Notes (e.g. other results reported): 15 of 85 individuals (17.6%) in test table group (including 13 Grade 1 and 2 Grade 2); 10 of 90 (11.1%) standard table group (including 9 Grade 1 and 1 Grade 2) Time to pressure ulcer incidence Outcome type: time‐to‐event Time points: 5 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): see above Definition (including ulcer stage): see above Dropouts: ITT analysis Notes: these data were read by review authors based on raw incidence data and days: 11 in day 0, 3 in day 1, 1 in day 3, and 0 in day 5 in test table group; 7 in day 0, 1 in day 1, 2 in day 3, and 0 in day 5 in standard table group. lnHR 0.48, selnHR 0.66 estimated by the review authors by using 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: No
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Included patients were randomised to either the standard operating table configuration or the test configuration" Comment: the method of randomisation was not reported.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Outcome group: primary outcome Quote: "Patients were also kept unaware of the configuration [experimental intervention]" Comment: unclear risk of bias because it is unclear if personnel were blinded.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome group: primary outcome Quote: "The postoperative nurses who assessed the skin condition were unaware of the patient assignment." Comment: low risk of bias because pressure ulcer incidence outcome assessment was blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome group: primary outcome Quote: "Missing values were substituted in concordance with baseline carry forward principle. Statistical analysis was based on the intention to treat principle" Comment: low risk of bias because ITT analysis was conducted.
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.