Shively 1988.

Methods	RCT with 2‐group design (frequency of turning). In addition, comparative analysis of body positions without counterbalance/cross‐over Pre‐specified analysis: 3‐factor mixed‐model ANOVA for group (turning frequency), position and time of measurement (main effect and interactions), univariate ANOVA for position and time of measurement. Contrast comparisons of all significant ANOVA results. Pre‐specified within‐subject analysis of good lung down vs bad lung down for unilateral lung disease subgroup (paired t test)
Participants	30 coronary artery bypass surgery adults within 24 hours of surgery (mean 9 hours ± 2.34) who were haemodynamically stable, had oximeter system in situ for continuous monitoring of SvO2 and were extubated (mean 3 hours ± 2.18 before the study) Sex (M/F) 23/7 (all females in group 2), mean age 59 years ± 9.7 Mean FiO2 (calculated) 0.426 ± 0.069 Exclusion criteria: chronic or terminal pulmonary disease such as COPD, tuberculosis or lung cancer or any portion of the lung removed, or cardiac arrest in postoperative period Subgroup classification (CXR within 24 hours of surgery): left unilateral lung pathology (group 1 = 6, group 2 = 6), right unilateral lung pathology (group 1 = 0, group 2 = 1), bilateral lung pathology (group 1 = 4, group 2 = 5), normal CXR (group 1 = 5, group 2 = 3) Termination criteria: (1) at participant's request, (2) unable to maintain a position for the specified time or (3) haemodynamically unstable during study (arterial pressures, venous pressures and CO could not be maintained within the participant's normal range) Setting: 3 critical care units in 3 major hospitals in Austin, Texas, USA, from June to December 1985
Interventions	Group 1 (n = 15): 1‐hourly turns (lateral positioning schedule) for 4 hours Group 2 (n = 15): 2‐hourly turns (lateral positioning schedule) for 8 hours Periods: supine position (baseline) followed by lateral positioning schedule of right lateral, 45 degrees sitting, left lateral, and supine positions. Note: lateral positioning schedule sequential and identical for both groups
Outcomes	SvO2 at 0 minutes, 15 minutes and 1 hour (both groups), with SvO2 at 2 hours for group 2
Standard management	Same oxygen level throughout study (n = 29). All medications listed with numerator for each medication. Nipride infusion (n = 18), ≥ 1 dose of morphine given during study (n = 18), decreasing use of intravenous nitrates throughout study Comment: vasoactive medication not controlled during study
Position description	Degree of lateral rotation and angle verification method not described 20 degrees HOB elevation for all body positions, except sitting position had 45 degrees HOB elevation. HOB elevation verification method: checked with goniometer
Washout period	Not described
Notes	No sample size calculation described. Individual participant data tabulated. Unclear whether 2‐hour data were entered in real time or were extrapolated for 4 participants (group 2) turned 10 to 20 minutes earlier than 2‐hour limit (turned because of discomfort) For subgroup analysis (n = 13), unclear whether repeated measures (3 or 4 depending on allocated group) were averaged Comment: Sequence was not randomized; therefore comparison between body positions (within‐subject difference) was not valid for extraction. No data were extracted for meta‐analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quotation: "randomly assigned the patients to one of two groups". No further description
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not described
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Not described Comments: unclear whether subgroup classification (CXR assessment of lung pathology) was blinded, but omission unlikely to bias primary outcome reporting. Furthermore, objective outcome measure taken from digital display of continuous physiological monitoring system; therefore, lack of outcome assessor blinding unlikely to bias results
Incomplete outcome data (attrition bias) All outcomes	High risk	68 consented, 26 excluded (could not start protocol) and 12 withdrawn (could not finish protocol); unclear whether exclusion before randomization. Even group numbers, no missing data points for 30 “as treated” participants. However, withdrawals > 20% (group allocation not identified). Rationale for exclusion/withdrawal provided (extended intubation or haemodynamic instability did not meet inclusion criteria (n = 21), inability to maintain position or haemodynamic instability met termination criteria (n = 9), restlessness or nausea (n = 2), technical problems with SvO2 monitor (n = 6)) Comment: no intention‐to‐treat analysis; therefore, high risk of attrition bias for parallel‐group (turning frequency) analysis
Selective reporting (reporting bias)	Low risk	Method of analysis conducted as pre‐specified and consistent with stated aims and hypotheses
Other bias	High risk	Non‐uniform unbalanced study design for analysis of 'body position' effects. Standard management may not have been equally applied across groups and periods, as titration of vasoactive medications/fluids, use of PRBC and volume expanders were not controlled for Sequence and carryover effects acknowledged as major threats to internal validity. Vital signs and additional haemodynamic data gathered before and after each position change to assess for threats Comments: 'Sequence effect' testing (in context of body position effects) was meaningless (identical sequence order). Methods to minimize sequence and carryover effects bias were inadequate, with contradictory statements reported. Reported carryover effects were not apparent, but investigators also reported that group 2 ‘possibly experienced carryover effects’ (interaction found in univariate but not multi‐variate analyses). Group 2 had lower mean SvO2 values for sitting 45‐degree and supine 20‐degree positions compared with group 1, with a rationale for the effect accredited to extent and occurrence of pulmonary pathology (group 2 had fewer normal CXRs, 3 vs 5). Furthermore, risk of intervention bias for examining body position effects was high, as groups 1 and 2 had different duration of treatment and measurement intervals, with no control for group or period effects. Unclear whether group effects were confounded by selection and/or performance bias. Unclear if period effects or treatment‐by‐period interactions were sources of bias. If carryover was present, unlikely to be equally applied across treatments because of lack of balance and uniformity