Remolina 1981.

Methods	Cross‐over trial (3‐treatment, 3‐period design), unclear sequence order Method of analysis: 1‐way AVOVA Quotation: "Difference[s] between groups were tested with the Newman‐Keuls tests"
Participants	9 consecutive hospitalized patients with indwelling arterial catheter in situ who had unilateral or predominantly unilateral lung disease (atelectasis, consolidation, infiltrates, pleural effusion) on CXR Sex not described, age range 36 to 72 years Mean FiO2 (calculated) 0.407 ± 0.231, Puritan Bennett MA‐1 volume‐limited ventilator (n = 1), otherwise spontaneously breathing (n = 8) Diagnosis: pneumonia ± aspiration (n = 6), bronchogenic or metastatic cancer (n = 2), bronchogenic cancer with pneumonia (n = 1) Subgroup classification: right lung pathology (n = 2), left lung pathology (n = 7) Setting: not described (study authors from USA)
Interventions	Right lateral, left lateral and supine positions (duration and sequence unknown) Lateral positions analysed according to bad lung down and good lung down only
Outcomes	Arterial blood gas pressures (PaO2) at 10 minutes (calculated P/F ratio for this review, as raw data for FiO2 and PaO2 were tabulated) Other co‐primary outcomes reported but not relevant for this review were PaCO2 and pH
Standard management	FiO2 unchanged from level set as part of management of the disease (FiO2 monitored with fuel‐cell oxygen analyser)
Position description	Not described
Washout period	Not described
Notes	No sample size calculation described For each body position, 11 results from 9 participants (data collected on 2 consecutive days for 2 participants; all other participants (n = 7) had data collected once for each body position) Summary statistics (mean and SE for each body position) included unit of analysis error for meta‐analysis. Comparison between lateral positions (within‐subject difference) was calculated from individual participant data Comments: extracted data adjusted with second set of data from 2 participants with repeated measures removed from analysis to avoid a unit of analysis error (i.e. effect estimate from first day of data collection). Unclear supine position order; therefore, comparison between each lateral position and supine position not valid for extraction No description of informed consent or review by ethics committee No reply to fax correspondence sent to primary investigator requesting further information about study design and results
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Random order of positions Quotation: "...supine, right lateral or left lateral position; which were assumed in random order". 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 Comment: objective outcome measures taken from ABG analyser; therefore, lack of outcome assessor blinding unlikely to bias results
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing data, as all raw data presented in a table
Selective reporting (reporting bias)	Unclear risk	Difference in data collection methods between participants, with no explanation given. All pre‐specified outcomes reported. However, test statistic provided for each body position did not identify paired comparison Comments: unclear whether planned paired analysis of ‘groups’ referred to sequence or specific body positions. Unclear whether analysis of data from consecutive days was planned for all participants. Unclear if selective outcome reporting occurred, as method of analysis provided insufficient information
Other bias	Unclear risk	No baseline position described. Insufficient detail on sequence. Sequence (group) size unknown. Body position duration not stated; therefore, unknown whether washout was applied after data collection Comment: unknown whether participants were in the same body position before commencing the study and during the first treatment period (If no turning was required for the first period, possible bias due to differences in treatment duration and data collection methods). Comments: Unclear whether cross‐over design was uniform and balanced. Highly probably that the study did not control for carryover nor sequence effects because details are lacking. Therefore, unclear if carryover, sequence or period effects or treatment‐by‐period interactions were sources of bias