Choi 2006.

Methods	RCT with parallel groups Approved by the Medical Ethics Committee of the University of Amsterdam (Amsterdam, The Netherlands), and informed consents obtained from all participants Site: Academic Medical Center, University of Amsterdam, The Netherlands Setting: university hospital Dates of data collection: December 2003 to March 2005
Participants	46 adults scheduled to undergo a surgical procedure of ≥ 5 hours Exclusion criteria: history of any lung disease, use of immunosuppressive medication, recent infections, previous thromboembolic disease or recent admission to ICU for ventilatory support
Interventions	Treatment group: tidal volume 6 mL/kg (IBW) and PEEP 10 cmH2O (n = 24 randomized; n = 21 analysed) Control group: tidal volume 12 mL/kg (IBW) and no PEEP (n = 22 randomized; and n = 19 analysed) The ventilatory protocol consisted of volume‐controlled mechanical ventilation at an FiO2 of 0.4, inspiratory/expiratory ratio of 1:2 and a respiratory rate adjusted to normocapnia. If the surgical procedure exceeded 5 hours, anaesthesiologists were allowed to change the ventilation strategy
Outcomes	Relevant to this review Invasive ventilation < 7 days Mortality during hospital stay (taken as < 30 days) Others Bronchoalveolar coagulation: thrombin‐antithrombin complexes, soluble tissue factor, factor VIIa, soluble thrombomodulin, activated protein C and fibrinolytic activity
Notes	Funding: support provided solely from institutional or departmental sources (or both) Declaration of interest: none mentioned Participants were followed up until hospital discharge or death Volume per body weight: predicted body weight calculated based on the equation used by the ARDS Network in their clinical trials: predicted body weight of men: equal to 50 + 0.91 (centimetres of height – 152.4); women: equal to 45.5 + 0.91 (centimetres of height – 152.4)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "randomization was performed by drawing a presealed envelope."
Allocation concealment (selection bias)	Low risk	Quote: "randomization was performed by drawing a presealed envelope."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not mentioned
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants accounted for and low rate of dropout
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Low risk	Groups well balanced Not intention‐to‐treat: quote: "five patients were randomized but excluded from final analysis, because the initial surgical procedure was converted by the surgeon into another shorter operation (< 3 hours). One patient was randomized, but no lavages were performed upon the surgeon's request after induction of anaesthesia."