Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Prevention of pressure ulcers
Systematic review	98 people with expected intensive care unit stay of >3 days Data from 1 RCT	Risk of new pressure ulcers 6/49 (12%) with low-air-loss beds in intensive care 25/49 (51%) with standard intensive-care beds	RR 0.24 95% CI 0.11 to 0.53 The review reported that the intensive-care bed was poorly described, allocation concealment was unclear, and outcome assessment was not blinded	Moderate effect size	low-air-loss beds
Systematic review	221 people 2 RCTs in this analysis	Risk of pressure ulcers 40 days 12/111 (11%) with low-air-loss beds 37/110 (34%) with static air overlay	RR 0.33 95% CI 0.16 to 0.67 P = 0.002	Moderate effect size	low-air-loss beds
RCT	62 people in intensive care In review	Development of pressure ulcers 3/30 (10%) with low-air-loss beds 6/32 (19%) with alternating-pressure mattresses	P = 0.35 The RCT may have been underpowered to detect a clinically important difference between groups		Not significant