Conine 1990.

Study characteristics
Methods	Study objective: to determine the efficacy of the alternating air mattress overlay and the silicone mattress overlay in preventing pressure ulcers Study design: sequential randomised controlled trial Study grouping: parallel group Duration of follow‐up: 3 months Number of arms: 2 Single centre or multi‐site: single centre Study start date and end date: study took place between 1985 and 1988 Setting: extended care facility for neurological conditions
Participants	Baseline characteristics Inclusion criteria: patients in extended care facility for neurological conditions, 18 to 55 years old, with no evidence of skin breakdown for at least 2 weeks prior to the study, and who were at high risk of developing ulcers according to the Norton's Scale (i.e. less than the score of 14) Exclusion criteria: the status of high risk changed during the study Sex (M:F): 31:41 in alternating air mattress; 29:47 in Silicore Age (years): mean 38.8 (SD 13.0) in alternating air mattress; 35.6 (13.0) in Silicore Baseline skin status: mean Norton score 12.9 (SD 2.1) in alternating air mattress; 12.4 (2.3) in Silicore Group difference: no difference Total number of participants: 187 randomised; 148 analysed Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Alternating air mattress Description of interventions: "... made of a heavy duty plastic material with honey‐combed 10 cm (4 inch) air cells which alternately inflate and deflate by an electrically driven pump" placed over a standard hospital spring mattress or a 10 cm foam and supported by standard hospital bed frames NPUAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: usual care (including turning every 2 or 3 hours) Number of participants randomised: n = 93 Number of participants analysed: n = 72 Silicore mattress overlay Description of interventions: "... composed of siliconized hollow fibres covered in waterproofed cotton" placed over a standard hospital spring mattress or a 10 cm foam and supported by standard hospital bed frames NPUAP S3I classification: non‐powered, reactive fibre‐filled surface Co‐interventions: usual care (including turning every 2 or 3 hours) Number of participants randomised: n = 94 Number of participants analysed: n = 76
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 3 months Reporting: fully reported Measurement method (e.g. scale, self‐reporting): measured using the Exton‐Smith scale (0 = none; 1 = persistent erythema in an irregular ill‐defined area; 2 = localised blister with distinct edges indicating early pigmentation with heat and induration; 3 = superficial sore extending into the subcutaneous fat with irregular rolled skin edges, dark pigmentation and a drainage; 4 = deep sore extending into deep fascia in which bone can be identified at the base of ulceration, with profuse drainage and necrosis; 5 = gangrenous sore with profuse multiple drainages, extensive necrosis, and resultant osteomyelitis and septic arthritis) Definition (including ulcer stage): the first appearance of any ulcers (scores of Grade 1 or above defined using Exton‐Smith scale) Dropouts: 21 missing data (including 2 death, 19 discomfort, 0 transferred) in alternating air mattress overlay; 18 (including 0 death, 17 discomfort, 1 transferred) in Silicore overlay Notes (e.g. other results reported): 39 individuals (with ulcers of any stages) in alternating air mattress; 45 individuals (with ulcers of any stages) in Silicore. Numbers of ulcers by grade reported also, but not extracted. Time to pressure ulcer development Reporting: not reported Support‐surface‐associated patient comfort Reporting: partially reported Measurement method (e.g. scale, self‐reporting): not described Definition: discomfort as a reason for dropout Drop outs: not described Notes: 19 of 93 in alternating air mattress; 17 of 94 in Silicore All reported adverse events using allocated support surfaces Reporting: not reported Health‐related quality of life (HRQOL) Reporting: not reported Cost‐effectiveness Notes: total overall cost per year of use presented in cost analysis paper by overlay groups: USD 771 in air overlay group and USD 500 in silicone overlay group Outcomes that are not considered in this review but reported in trials: Healing duration of ulcers Severity of new ulcers Acceptability measured for 40 patients in total (20 from each group)
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "A modified sequential clinical trial ... was used to assign subjects randomly to one of the two mattresses in groups of 20" Comment: the method of randomisation was not specified.
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 Comment: no information provided but understandably difficult to blind participants and personnel.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome group: primary outcome Quote: "The research assistant ... was responsible for the assessment of all outcome measures. She ... was not informed about the study" Comment: low risk of bias because blinding is likely applied.
Incomplete outcome data (attrition bias) All outcomes	High risk	Outcome group: primary outcome Quote: "Thirty‐nine subjects did not complete the trial for reasons shown in Table 3" Comment: high risk of bias because over 20% of 187 randomised individuals missed and most of the dropouts were due to discomfort.
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.