Outcomes	Results
Comparison: Alternating pressure (active) air surfaces compared with undefined 'standard hospital surfaces'
Proportion of participants developing a new pressure ulcer (median follow‐up duration 15 days, minimum 10 days, maximum 16 days or unspecified)	All four studies (830 participants) reported this outcome and consistently showed that alternating pressure (active) air surfaces could reduce the proportion of participants developing a new pressure ulcer compared with the undefined 'standard hospital surfaces' (Andersen 1982; Bliss 1967; Laurent 1998; Sanada 2003).