Banasik 2001.

Methods	Randomized cross‐over trial (3‐treatment, 6‐sequence, 3‐period design) Pre‐specified analysis: univariate ANOVA with repeated measures for all dependent variables
Participants	12 mechanically ventilated adults with PA catheter who met critical illness criteria (PaO2 ≤ 70 mmHg on current ventilator settings with supplemental oxygen or cardiac index ≤ 2.0 L/min/m2) Sex (M/F) 7/5, mean age 65 years ± 15.5 Mean FiO2 0.75 ± 0.18, mean PEEP 8.0 cmH2O ± 3.5 (n = 8), mean Vt 775 mL ± 89 with A/C mode Baseline: mean PaO2 60.5 mmHg ± 8.7 (n = 8), mean CI 1.5 L/min/m2 ± 0.3 (n = 5), 1 participant met both inclusion criteria Diagnosis: ischaemic heart disease (n = 3), valvular heart disease (n = 2), pericarditis (n = 1), respiratory failure (n = 3), hyponatraemia (n = 1), liver failure (n = 1), pancreatitis (n = 1) Pulmonary co‐morbidity/possible subgroup analysis (based on pre‐study CXR): bilateral infiltrates or atelectasis (n = 5), right‐sided atelectasis or effusion (n = 4), left‐sided atelectasis or effusion (n = 2) and normal CXR (n = 1) Setting: ICU and cardiac ICU in urban 450‐bed hospital in northwestern USA
Interventions	Left lateral, right lateral and supine positions for 20 minutes Sequences/groups: SLR, SRL, RLS, RSL, LRS, LSR
Outcomes	Tissue oxygen delivery measures (HR, CO, arterial and mixed venous blood gases (PaO2, SaO2, SvO2), CaO2 and VO2), serum lactate as a measure of the adequacy of tissue oxygenation, resp. rate (possibly secondary outcome) All measures taken between 15th and 20th minutes Other co‐primary outcomes reported but not relevant for this review were pH, PaCO2 and HCO3
Standard management	Ventilator settings unchanged during trial and no tracheal suctioning. All participants received sedative and pain medication, but not during data collection. No muscle relaxants given and no change in vasoactive medication dose rates
Position description	45 degrees lateral rotation, passively turned with participants instructed not to assist, commercial foam wedge to maintain angle Angle verification method: protractor No HOB elevation with single pillow under the head for all positions
Washout period	15‐minute stabilization period (data collected over 5 minutes before next position change)
Notes	Post hoc power analysis performed (effect size 0.558 to detect mean difference in CaO2 of 2.3%, CO of 6.7% and lactate of 7.5%, 1‐β = 0.8, α = 0.05) CaO2 calculations included Hb level taken from first arterial line sample only, no active bleeding reported Comments: no extractable summary statistics for meta‐analysis because of unit of analysis error (reported mean and SD for each body position). Additional data no longer available (personal communication from principal investigator)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomized positioning sequence. Participants assigned study number and associated position sequence based on order of entry into the study
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 Comment: objective outcome measures taken from digital display of continuous physiological monitoring system or calibrated blood gas analyser; therefore, lack of outcome assessor blinding unlikely to bias results
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	All participants completed study. Numerator for each outcome stated within ANOVA tables, consistent with sample size except for mixed venous data Quotation: "because of some missing data there was insufficient power to evaluate the effect of position on venous blood gases and VO2" Comment: impact of missing VO2 and other venous gas measures (SvO2) unclear, as measures were part of the evaluation of tissue oxygen delivery
Selective reporting (reporting bias)	High risk	Mixed venous sampling (i.e. VO2 and SvO2) not included within results or analysis because of missing data Comment: high risk of selective reporting bias for outcomes measuring tissue oxygen delivery Other reporting issue: unclear whether subgroup analysis based on location of lung pathology (unilateral vs bilateral) was pre‐planned, but such analysis was unlikely to influence primary reporting
Other bias	Unclear risk	No baseline position described. Uniform cross‐over design with unclear balance (no sequence group numbers, small sample size (n = 12) for 6 sequences). No baseline characteristics presented except for inclusion criteria. Unclear whether any baseline differences between groups (sequences) occurred by chance, as allocation concealment is unclear Comment: unclear whether sequence effects or treatment‐by‐period interactions may be sources of bias. If carryover present, unclear whether equally applied across treatments because of unclear balance. Carryover effects may be due to short active and possibly insufficient washout. Unclear risk of carryover bias Data collection between 15th and 20th minutes following each turn; therefore, unclear whether all treatments (body positions) were measured in the same way (i.e. time elapsed before measurement) Comment: small differences in measurement intervals between participants (as possible source of bias) unlikely to yield clinically important differences within individuals (within‐subject variability)