Gray 1994.

Study characteristics
Methods	Study objective: to fully evaluate and define the clinical abilities of the standard 130 mm contract mattress and the Softform mattress in regards to their ability to provide the patient with adequate pressure reduction, so as to prevent pressure sore formation, and provide the patient with adequate comfort. 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 from orthopaedic trauma, vascular and medical oncology units without breaks in the skin (Waterlow score ≥ 15) Exclusion criteria: not described Sex (M:F): overall 66:104; 33:57 in Softfoam mattress; 33:47 in Standard 130 mm NHS foam mattress Age (years): overall mean 76 (range 35 to 99); mean 76 (SD 10.53) in Softfoam mattress; 74 (9.96) in Standard 130 mm NHS foam mattress Baseline skin status: mean Waterlow 18.03 (SD 3.23) in Softfoam mattress; 16.01 (2.58) in Standard 130 mm NHS foam mattress Group difference: no difference Total number of participants: n = 170 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Softform mattress Description of interventions: Softform mattress ... supplied by Medical Support Systems Ltd (Cardiff) (Gray 1994); " A high specification foam mattress ... " from Invacare website (https://www.invacare.co.uk/invacare-softform-premier-maxiglide-mattress-ma-83sfpremgen) NPIAP S3I classification: non‐powered, reactive foam surface; high‐specification foam Co‐interventions: not described Number of participants randomised: n = 90 Number of participants analysed: not given Standard 130 mm foam mattress Description of interventions: standard 130 mm foam mattresses ... supplied by Recticel Ltd. (Midlands) NPIAP S3I classification: non‐powered, reactive foam surface Co‐interventions: not described Number of participants randomised: n = 80 Number of participants analysed: not given
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: not described Reporting: partially reported Measurement method (e.g. scale, self‐reporting): not described Definition (including ulcer stage): not described Dropouts: not described Notes (e.g. other results reported): percentage of participants developing new ulcers 7.1% (n = 6) in Softform; 34.2% in standard, Chi2 P < 0.001 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): assessed using a standardised question and a visual rating scale, administered: 'Which phrase best describes the mattress you have occupied during your stay in hospital?' (very uncomfortable, uncomfortable, adequate, comfortable, very comfortable, no response obtained) Definition: not described Dropouts: no missing Notes: very uncomfortable 0/ uncomfortable 0/ adequate 6/ comfortable 62/ very comfortable 11/ no response 11 of 90 in Softform; 0/2/44/26/0/8 of 80 in standard. comfortable or very comfortable 81.1% in Softform, 32.5% in standard 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: "Allocation of mattresses was by patient randomisation on admission ... randomly allocated to one of the two types of mattress using unmarked envelopes" Comment: unclear if a proper randomisation method was applied.
Allocation concealment (selection bias)	Unclear risk	Quote: "randomly allocated to one of the two types of mattress using unmarked envelopes" Comment: unclear if allocation was appropriately 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	Unclear risk	Outcome group: pressure ulcer outcome Comment: no information provided. Outcome group: comfort outcome Comment: high risk of bias because it is unlikely that patients who self‐reported their comfort responses are blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Outcome group: all outcomes Quote: "A number of patients were excluded from the study because the Waterlow score awarded by the ward staff differed greatly from that of the researcher" Comment: unclear risk of bias because the number of exclusions is unclear and unclear if this exclusion was post‐randomisation.
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.