Jiang 2014.

Study characteristics
Methods	Study objective: to investigate the efficacy of static low‐air‐loss mattress (static LALM) and power pressure air mattress (PPAM) in prevention of pressure ulcers Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 5 days after surgery Number of arms: 2 Single centre or multi‐site: multi‐site Study start date and end date: not described Setting: hospitals
Participants	Baseline characteristics Inclusion criteria: age ≥ 18 years, male or female with Braden score ≤ 16 points, general anaesthesia for surgery with operating time ≥ 120 min, admitted to the intensive care unit (ICU) or surgical wards after surgery, clear consciousness, able to express their feelings correctly, had contraindications for using air mattress (doctor’s orders: lying on hard‐bed or flat‐bed), completed informed consent and related information Exclusion criteria: refused to participate in research; in critical condition and repositioning limited by doctor’s orders; using ice blanket; shed from intervention less than 72 hours; unable to determine the efficacy; incomplete data on the efficacy; or safety judgment. Sex (M:F): overall 621:453 Age (years): overall mean 57.94 (SD 15.54) years (range 18 to 88) Baseline skin status: overall mean Braden scores 13.15 (SD 2.25) (range 6 to 17) Group difference: no difference Total number of participants: n = 1074 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Static air mattress Description of interventions: static air mattress (®WAFFLE static air mattress, EHOB, United States) NPIAP S3I classification: non‐powered, reactive air surface Co‐interventions: repositioning every 2 hours Number of participants randomised: n = 562 Number of participants analysed: n = 562 Dynamic air mattress Description of interventions: dynamic air mattress (Sanma mattress manufacturing factory, Shanghai, China) NPIAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: repositioning every 2 hours Number of participants randomised: n = 512 Number of participants analysed: n = 512
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: Reporting: partially reported Measurement method (e.g. scale, self‐reporting): graded by the NPIAP 2007 criteria Definition (including ulcer stage): Dropouts: no missing Notes (e.g. other results reported): static air mattress group 1.07% (6/562); dynamic air mattress 0.98% (5/512) χ2 = 0.148, P = 0.882 Time to pressure ulcer development Not reported Support‐surface‐associated patient comfort Outcome type: binary Time points: post‐operative 5 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): asking patients’ feelings after using the mattress 1 = very uncomfortable, 2 = uncomfortable, 3 = just comfortable, 4 = comfortable, 5 = very comfortable Definition: the level of patients’ comfort Dropouts: 80 of 562 missing in static air mattress; 100 of 562 missing in dynamic air mattress Notes: 68 of 482 patients having a comfort level rating more than the median of 4 in static air mattress and 414 of 482 less than the median level; 68 of 462 more than the median of 4 in dynamic air mattress and 394 less than the median (Chi2 = 0.071, P = 0.789) All reported adverse events using allocated support surfaces Not reported Health‐related quality of life (HRQOL) Not reported Cost‐effectiveness Not reported
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "We used a random number table to randomize and parallel control design" Comment: low risk of bias because the sequence generation process is proper.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
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	Low risk	Outcome group: ulcer incidence Comment: low risk of bias because intention‐to‐treat (ITT) analysis performed. Outcome group: comfort Comment: unclear risk of bias because the rates of missing data in both groups are between 10% to 20%.
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.