3. Pressure ulcer incidence results reported in studies that compared different types of alternating pressure (active) air surfaces.

Study ID	Results		Comment
Comparison: alternating pressure (active) air surfaces compared with other types of alternating pressure (active) air surfaces
Demarre 2012	Alternating pressure (active) air surfaces (Hill‐Rom ClinActiv) Proportion of participants developing a new pressure ulcer: 17/298 (5.7%) Time to pressure ulcer development: median time 5.0 days (IQR 3.0 to 8.5)	Alternating pressure (active) air surfaces (Hill‐Rom Alto mattress) Proportion of participants developing a new pressure ulcer: 18/312 (5.8%) Time to pressure ulcer development: median 8.0 days (IQR 3.0 to 8.8)	Proportion of participants developing a new pressure ulcer: RR 0.99 (95% CI 0.52 to 1.88). Time to pressure ulcer development: Mann‐Whitney U‐test = 113, P = 0.182 for median time to ulcer incidence; Kaplan Meier plot reported (log‐rank Chi2 = 0.013, df = 1, P = 0.911); HR 0.96 (95% CI 0.50 to 1.87) estimated by the review authors using the methods of Tierney 2007.
Gray 2008	Alternating pressure (active) air surfaces (hybrid air surfaces: Softform Premier Active Mattress) Proportion of participants developing a new pressure ulcer: 4/50 (7.7%)	Alternating pressure (active) air surfaces Proportion of participants developing a new pressure ulcer: 4/50 (7.7%)	Proportion of participants developing a new pressure ulcer: RR 1.00 (95% CI 0.26 to 3.78).
Hampton 1997	Alternating pressure (active) air surfaces (hybrid air surfaces: Cairwave Therapy System) Proportion of participants developing a new pressure ulcer: 0/36 (0.0%)	Alternating pressure (active) air surfaces Proportion of participants developing a new pressure ulcer: 0/unspecified number	Proportion of participants developing a new pressure ulcer: summary estimate not estimable due to the lack of data.
Nixon 2006	Alternating pressure (active) air surfaces (mattresses) Proportion of participants developing a new pressure ulcer: 101/982 (10.3%) Time to pressure ulcer development: see comments	Alternating pressure (active) air surfaces (overlays) Proportion of participants developing a new pressure ulcer: 106/989 (10.7%) Time to pressure ulcer development: see comments	Proportion of participants developing a new pressure ulcer: RR 0.96 (95% CI 0.74 to 1.24). Time to pressure ulcer development: log‐rank test P = 0.759; HR 0.96 (95% CI 0.73 to 1.26) estimated by the review authors using the methods of Tierney 2007.
Rafter 2011	Alternating pressure (active) air surfaces (hybrid air surfaces: Dyna‐Form Mercury Advance) Proportion of participants developing a new pressure ulcer: 0/5 (0.0%)	Alternating pressure (active) air surfaces (hybrid air surfaces: Softform Premier Active) Proportion of participants developing a new pressure ulcer: 2/5 (40.0%)	Proportion of participants developing a new pressure ulcer: RR 0.20 (95% CI 0.01 to 3.35).
Taylor 1999	Alternating pressure (active) air surfaces (hybrid air surfaces: Pegasus Trinova) Proportion of participants developing a new pressure ulcer: 0/22 (0.0%)	Alternating pressure (active) air surfaces Proportion of participants developing a new pressure ulcer: 2/22 (9.1%)	Proportion of participants developing a new pressure ulcer: RR 0.20 (95% CI 0.01 to 3.94).
Theaker 2005	Alternating pressure (active) air surfaces (hybrid air surfaces: KCI TheraPulse bed with low‐air‐loss feature) Proportion of participants developing a new pressure ulcer: 3/30 (10.0%)	Alternating pressure (active) air surfaces (hybrid air surfaces: Hill‐Rom Duo mattress) Proportion of participants developing a new pressure ulcer: 6/32 (18.8%)	Proportion of participants developing a new pressure ulcer: RR 0.53 (95% CI 0.15 to 1.94).

IQR ‐ interquartile range