Sanada 2003.

Study characteristics
Methods	Study objective: to examine the effectiveness of a new overlay for at‐risk patients who require head elevation Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: not described Number of arms: 3 Single centre or multi‐site: single centre Study start date and end date: August 1999 to September 2000 Setting: a general acute care unit (hospital)
Participants	Baseline characteristics Inclusion criteria: had a Braden score ≤ 16, bed bound, pressure ulcer‐free, required head elevation Exclusion criteria: not described Sex (M:F): 14:15 in double‐layer; 15:11 in single‐layer; 13:14 in standard hospital mattress Age (years): mean 69.5 (SD 14.7) in 29 participants in double‐layer; 73.9 (10.4) in 26 participants in single‐layer; 70.6 (10.7) in 27 participants in standard hospital mattress Baseline skin status: Braden 12.5 (SD 1.7) in double‐layer; 12.1 (1.4) in single‐layer; 12.7 (1.7) in standard; free of pressure ulcers Group difference: no difference Total number of participants: n = 108 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Double‐layer air‐cell overlay Description of interventions: "... a new double‐layer air‐cell overlay ... incorporated an extra layer ... reconstructed the air‐cell design from the originally round‐shaped cell to a newly designed cylinder‐shaped cell ... (Tricell®, Cape Ltd, Japan), dimensions (cm): 191 (l) x 84 (w) x 10 (h) ... consist of multiple air cells that are 'dynamic' in nature ‐ the cell pressure was alternated at 5‐minute intervals ... two layers consisting of 24 narrow cylinder‐shaped air‐cells" NPIAP S3I classification: powered, alternating pressure (active) surface Co‐interventions: no difference between groups; repositioning every 2 hours, special skin care, and nutritional intervention where necessary Number of participants randomised: n = 36 Number of participants analysed: n = 29 Single‐layer air‐cell overlay Description of interventions: a single‐layer air‐cell overlay (Air Doctor®, Cape Ltd, Japan), dimensions (cm): 191 (l) x 84 (w) x 7.5 (h) ... consist of multiple air cells that are 'dynamic' in nature ‐ the cell pressure was alternated at 5‐minute intervals ... only one layer and consists of 20 round air cells NPIAP S3I classification: powered, alternating pressure (active) surface Co‐interventions: no difference between groups; repositioning every 2 hours, special skin care, and nutritional intervention where necessary Number of participants randomised: n = 37 Number of participants analysed: n = 26 Standard hospital mattress Description of interventions: made of polyester and used widely in Japanese hospitals (Paracare®, Paramount Beds Ltd, USA), dimensions (cm): 191 (l) x 91 (w) x 8.5 (h) NPIAP S3I classification: standard hospital surface Co‐interventions: no difference between groups; repositioning every 2 hours, special skin care, and nutritional intervention where necessary Number of participants randomised: n = 35 Number of participants analysed: n = 27
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): measured by nurses using National Pressure Ulcer Advisory Panel (NPIAP) classification system Definition (including ulcer stage): the number of individuals with pressure ulcers of any stage Dropouts: 1 discontinued due to mattress malfunction, 4 died, and 2 head elevation ≤ 30 in double‐layer; 2 discontinued due to discomfort or interfered with treatment, 2 died, and 7 head elevation ≤ 30 in single‐layer; 1 died and 7 head elevation ≤ 30 in standard mattress Notes (e.g. other results reported): 1 of 29 (stage II) in double‐layer group; 5 of 26 (1 stage I; 4 stage II) in single‐layer group; 10 of 27 (4 stage I; 6 stage II) in standard hospital mattress Time to pressure ulcer development Reporting: not reported. 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)	Unclear risk	Quote: "The subjects were randomly allocated to the groups by sequentially‐labelled sealed envelopes." Comment: unclear risk of bias because the method of random number generation was not described.
Allocation concealment (selection bias)	Unclear risk	Quote: "The subjects were randomly allocated to the groups by sequentially‐labelled sealed envelopes." Comment: unclear risk because it is unclear if the envelopes were opaque.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: no information provided.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: no information provided.
Incomplete outcome data (attrition bias) All outcomes	High risk	Outcome group: all outcome (primary outcome) Comment: high risk of bias because 7 of 36 individuals randomised in double‐layer group; 11 of 37 in single‐layer group; and 8 of 35 in standard mattress excluded from 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.