Gavigan 1990.

Methods	RCT with 2‐group design Pre‐specified analysis: ANOVA, quotation: “for any differences between and within groups”
Participants	50 mechanically ventilated elective CABG surgery adults within 2 hours of surgery (each group included 1 participant with both CABG and aortic valve replacement); other inclusion criteria: SBP 90 to180 mmHg, DBP < 100 mmHg, HR < 120 beats/min, PEEP ≤ 5cmH2O (range 0 to 5) Sex (M/F) 42/8, mean 62.12 years ± 10.33 FiO2 (0.4 or 0.5) adjusted for optimal PO2, Vt 10 to 15 mL/kg with A/C mode (volume‐cycled MA1 device) Exclusion: asthma, COPD, tuberculosis, lung cancer, pneumothorax Termination criteria: PEEP > 5 cmH2O Setting: surgical CCU, Thomas Jefferson Unversity Hospital, Philadephia, Pennsylvania, USA, for 5‐month period
Interventions	Experimental group (n = 18): lateral positioning schedule for first 24 postoperative hours (turned every 2 hours between supine and alternating left lateral and right lateral positions) Control group (n = 32): supine immobilization for first 24 postoperative hours (maintained in supine position without turning)
Outcomes	Improved pulmonary status defined as a decrease in the incidence or severity or both of documented lung pathology relative to control group. Presence of lung pathology identified by CXR taken immediately postop (baseline) and daily for first 3 days; focus on identifying atelectasis (graded according to severity, type and location) and evidence of other lung pathology (pneumonia, pleural effusions, pulmonary oedema, postop pneumothorax) Length of hospital stay Other data collected and reported included presence of temperature > 38.2°C measured rectally (collected 1‐ to 4‐hourly over first 3 postop days) and length of ICU stay Other data collected and not reported included other vital signs, haemodynamic monitoring recorded hourly, time of extubation and post‐extubation ABG (unclear whether secondary outcomes or taken for monitoring purposes)
Standard management	Quotation: "Patients in both groups were treated the same in all aspects of care with the exception of turning". Post extubation, all participants began incentive spirometry once an hour for first postop day and chest physiotherapy immediately and every 4 hours, with morphine sulphate offered to all every 3 hours and up to a half‐hour before chest physiotherapy
Position description	45 degrees lateral rotation, commercial foam wedge, angle verification method not described. No other descriptions
Washout period	Not applicable for design
Notes	No sample size calculation described No description about reliability or validity of atelectasis scoring system Study tabulated frequencies according to postop day (days 1 to 3), type of atelectasis (lobar, segmental, discoid) and percentage with right‐ and left‐sided atelectasis of each type Comments: unclear whether participants were represented more than once within the results table. Atelectasis incidence reported (74% of sample, but unclear if at baseline or during any of the follow‐up periods) with no numerator with and without atelectasis for each allocated group at follow‐up periods. No extractable dichotomous data on CXR abnormalities for meta‐analysis. No summary statistics for any other outcome. Study information no longer accessible; attempt made to find study file (personal communication with principal investigator). No further information received
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomly assigned to experimental or control group, with no further description
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not described Comment: Caregiver awareness of group allocation may influence length of stay; unclear if lack of blinding may bias this result
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Radiologist documented evidence of lung pathology for CXR without awareness of group assignment. Single assessor of atelectasis scoring system unaware of group allocation. Blinding of other outcomes not described Comment: temperature and other objective outcome measures taken from real‐time physiological monitoring system; therefore, lack of outcome assessor blinding unlikely to bias these results
Incomplete outcome data (attrition bias) All outcomes	High risk	No intention‐to‐treat analysis conducted. Uneven group size (18 vs 32) due to withdrawal of one‐third of original experimental group (actual numerator not described) Withdrawals due to haemodynamic compromise following a turn (described as a transient drop in SBP < 100 mmHg that returned to baseline when immediately returned to the supine position) Comment: PEEP limit was sole termination criterion
Selective reporting (reporting bias)	Unclear risk	Aims, methods and results provided insufficient information for identification of all primary outcomes from secondary outcomes, including temperature and other vital signs Comment: inadequate reporting of dichotomous group data for postop atelectasis. No other data on CXR abnormalities. No summary data reported for length of stay in ICU or hospital. Frequency of temperature > 38.2°C analysed (P value and df reported), with no other vital signs analysed. Overall, unclear risk of selective reporting bias for primary vs secondary outcomes, as ambiguity between study purpose, outcomes collected and outcomes reported
Other bias	Low risk	Method of randomization considered adequate by investigators, as no difference found in baseline demographics and characteristics