Weingarten 2010.

Methods	RCT with parallel groups Mayo Clinic Institutional Review Board approved the investigation, and each participant gave written informed consent Site: Saint Mary's Hospital, Rochester, MN, USA Setting: university hospital Dates of data collection: unspecified
Participants	40 participants aged > 65 years undergoing major open abdominal surgery Exclusion criteria: significant pulmonary disease with abnormalities in spirometry consistent with either obstructive or restrictive pulmonary disease, active asthma (requiring chronic bronchodilator therapy), previous lung surgery, home oxygen therapy, significant cardiac dysfunction (left ventricular ejection fraction < 40%), BMI > 35 kg/m2
Interventions	Treatment group: tidal volume 6 mL/kg (IBW), PEEP 12 cmH2O and recruitment manoeuvres (after tracheal intubation, repeated at 30 and 60 min after the first recruitment and hourly thereafter) (n = 20) Control group: tidal volume 10 mL/kg (IBW), 0 PEEP (actual PEEP 2.5 cmH2O due to the intrinsic PEEP of the mechanical ventilator) and no recruitment manoeuvres (n = 20) In both groups, inspiratory/expiratory time ratio 1:2 and FiO2 0.5 (balance nitrogen)
Outcomes	Relevant to this review Pneumonia Hospital length of stay Pneumothorax (requiring chest tube placement) Mortality at 30 days (information retrieved from medical records, exact duration of follow‐up not mentioned but hospital length of stay with interquartiles from 3–20 days) Others Oxygenation Respiratory system mechanics Haemodynamic stability Serum levels of the interleukin‐6 and ‐8
Notes	Funding: entirely supported by the Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA Declaration of interest: none mentioned Volume per body weight: predicted (abstract) IBW (methods section), no further details
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Participants randomized to 1 of 2 ventilatory management strategies using a randomization schedule provided by the Division of Biostatistics
Allocation concealment (selection bias)	Unclear risk	Not mentioned
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	No loss to follow‐up
Selective reporting (reporting bias)	Low risk	All results provided
Other bias	Unclear risk	Quote: "patient characteristics and preoperative comorbidities were similar between the groups, with the exception that more patients in the low tidal volume group had documented coronary artery disease (P value = 0.044)."