Rafter 2011.

Study characteristics
Methods	Study objective: to determine the effect of the Dyna‐Form Mercury Advance Mattress versus Softform Premier Active Mattress on pressure ulcer incidence for those in high risk rehabilitation wards over a 1‐month period Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 1 month Number of arms: 2 Single centre or multi‐site: single centre Study start date and end date: not described Setting: hospital
Participants	Baseline characteristics Inclusion criteria: no existing skin damage or up to category 2 EPUAP pressure ulcers Exclusion criteria: unwilling to participate, re‐admitted with pressure ulcers and weighed above 25 stone Sex (M:F): 0: 5 in Dyna‐Form; and 4:1 in Softform Age (years): median 73 in Dyna‐Form; and 76.8 in Softform Baseline skin status: median Waterlow 21.1 (range 11 to 30) in Dyna‐Form; and 18.4 (15 to 26) Group difference: not specified Total number of participants: 10 Unit of analysis: individuals Unit of randomisation (per patient): individuals
Interventions	Intervention characteristics Dyna‐Form Mercury Advance Description of interventions: being a static mattress combined with a dynamic alternating system ... the foam is actually inside the alternating cells. The pump has a cycle of 10 minutes ... There is a CPR and static mode. It has an automatic pump that is also adjustable in two modes for patient comfort and ‘dynamic use’ (dynamic use refers to an alternating cell mattress driven by an electrical pump with air sacks which sequentially inflate and deflate to relieve pressure for short periods under the patient) ... the mattresses can be used as a static system when an alternating surface is not required. NPIAP S3I classification: powered, alternating pressure (active) air surface; hybrid mattress (active and reactive modes) Co‐interventions: not described Number of participants randomised: n = 5 Number of participants analysed: n = 5 Softform Premier Active Description of interventions: consists of a foam mattress with a dynamic underlay. The underlay alternates on a 2‐cell 10‐minute cycle time through the pump ... The pump is also able to assess the patient’s weight and adjusts the supply of an appropriate level of air to provide an alternating surface ... the mattresses can be used as a static system when an alternating surface is not required. NPIAP S3I classification: powered, alternating pressure (active) air surface; hybrid mattress (active and reactive modes) Co‐interventions: not described Number of participants randomised: n = 5 Number of participants analysed: n = 5
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: 1 month Reporting: fully reported Measurement method (e.g. scale, self‐reporting): defined by EPUAP system Definition (including ulcer stage): no. of patients with new ulcers of any stage Dropouts: no Notes (e.g. other results reported): 0 of 5 in Dyna‐Form; 2 of 5 in Softform (1 Stage 1 and 1 Stage 1 & 2) Time to pressure ulcer development Reporting: not reported Support‐surface‐associated patient comfort Outcome type: binary Time points: 1 month Reporting: partially reported Measurement method (e.g. scale, self‐reporting): self‐reported Definition: participants' opinions on the comfort aspects of the mattress Dropouts: 2 in each group Notes: 6 patients were able to respond to the patient questionnaire. All slept well in both groups. 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 considered to be at high risk of pressure ulcer development were randomly allocated ..." Comment: unclear risk of bias.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Outcome group: primary outcome Comment: high risk of bias because it was unlikely to be possible to blind ward staff who were trained in using both systems for this study.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Outcome group: primary outcome Quote: "Their skin was assessed daily for any changes or development of pressure ulcers by ward staff and by the co‐ordinator of the audit three times a week." Comment: high risk of bias because it was unlikely to be possible to blind ward staff.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Outcome group: primary outcome Comment: low risk of bias because of no missing. Outcome group: comfort Comment: high risk of bias because 2 of 5 missed in each group.
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.