Cavicchioli 2007.

Study characteristics
Methods	Study objective: to determine whether alternating low pressure or continuous low pressure is most effective in reducing the incidence of pressure ulcers in high risk patients Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 2 weeks Number of arms: 2 Single centre or multi‐site: multi‐site Study start date and end date: March 2004 to November 2006 Setting: acute, post‐acute and long‐term care settings of 3 hospitals
Participants	Baseline characteristics Inclusion criteria: those admitted to the unit or deemed "at risk" of pressure ulceration as defined by the Braden Pressure Ulcer Risk Assessment Scale (a total Braden score of ≤ 17 and mobility and activity sub‐scores of ≤ 3 respectively); their admission was expected to last at least 2 weeks and they had up to one grade I pressure ulcer Exclusion criteria: not at risk (Braden ≥ 17 and activity or mobility sub‐scales ≥ 3, respectively) Sex (M:F): 20:49 in alternating low pressure; 20:51 in continuous low pressure Age (years): mean 77 in alternating low pressure; 78 in continuous low pressure Baseline skin status: mean 11.4 (range 7 to 16) in alternating low pressure; 11.9 (6 to 17) in continuous low pressure Group difference: no difference Total number of participants: 170 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Alternating low pressure modality of Duo2 (Hill‐Rom) Description of interventions: Duo2 (Hill‐Rom), "... electrically powered, air‐filled mattresses in which adjacent cells inflate and deflate reciprocally underneath the patient" NPUAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: not described Number of participants randomised: n = 86 Number of participants analysed: n = 69 Continuous low pressure modality of Duo2 (Hill‐Rom) Description of interventions: continuous low pressure modality of Duo2 (Hill‐Rom) NPUAP S3I classification: powered, reactive air surface Co‐interventions: not described Number of participants randomised: n = 84 Number of participants analysed: n = 71
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 2 weeks Reporting: partially reported Measurement method (e.g. scale, self‐reporting): assessed by the external observer Definition (including ulcer stage): not described Dropouts: 17 dropouts in alternating low pressure (4 died, 8 discharged prior to assessment, 5 did not complete study due to non‐concordance (uncomfortable) and not agreeing to use the modality; 13 dropouts in continuous low pressure (5 died, 4 discharged prior to assessment, 4 did not complete study due to non‐concordance and not agreeing to use the modality). Notes (e.g. other results reported): 2 of 69 individuals (one Stage 1 and one Stage 2) in alternating low pressure; 1 of 71 individuals (Stage 2) in continuous low pressure. Time to pressure ulcer development Reporting: not reported Support‐surface‐associated patient comfort Reporting: not reported Notes: 5 dropouts due to discomfort and/or not agreeing to use the assigned modality in alternating low pressure; 4 dropouts due to discomfort and/or not agreeing to use the assigned modality in continuous low pressure. 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: "Patients in the treatment group were randomised to receive either continuous or alternating low pressure on the high‐tech mattress" 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	Low risk	Outcome group: primary outcome Quote: "... independently from the blinded randomised treatment group (who received the Duo2 high‐tech mattress)." Comment: low risk of bias because blinding method was implemented.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Outcome group: primary outcome Quote: "As there is no visible difference between these two modes, the external observer was blinded as to which one was in use. The external observers assessed all study patients' ... presence (or absence) and grade of both existing and new pressure ulcers" Comment: low risk of bias because outcome assessment was blinded.
Incomplete outcome data (attrition bias) All outcomes	High risk	Outcome group: primary outcome Comment: high risk of bias because of high proportions of dropouts in both groups and probably using incorrect analysis methods to address missing data.
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.