title: An updated study-level meta-analysis of randomised controlled trials on proning in ARDS and acute lung injury.
abstract: BACKGROUND
  In patients with acute lung injury (ALI) and/or acute respiratory distress syndrome (ARDS), recent randomised controlled trials (RCTs) showed a consistent trend of mortality reduction with prone ventilation. We updated a meta-analysis on this topic.
  
  
  METHODS
  RCTs that compared ventilation of adult patients with ALI/ARDS in prone versus supine position were included in this study-level meta-analysis. Analysis was made by a random-effects model. The effect size on intensive care unit (ICU) mortality was computed in the overall included studies and in two subgroups of studies: those that included all ALI or hypoxemic patients, and those that restricted inclusion to only ARDS patients. A relationship between studies' effect size and daily prone duration was sought with meta-regression. We also computed the effects of prone positioning on major adverse airway complications.
  
  
  RESULTS
  Seven RCTs (including 1,675 adult patients, of whom 862 were ventilated in the prone position) were included. The four most recent trials included only ARDS patients, and also applied the longest proning durations and used lung-protective ventilation. The effects of prone positioning differed according to the type of study. Overall, prone ventilation did not reduce ICU mortality (odds ratio = 0.91, 95% confidence interval = 0.75 to 1.2; P = 0.39), but it significantly reduced the ICU mortality in the four recent studies that enrolled only patients with ARDS (odds ratio = 0.71; 95% confidence interval = 0.5 to 0.99; P = 0.048; number needed to treat = 11). Meta-regression on all studies disclosed only a trend to explain effect variation by prone duration (P = 0.06). Prone positioning was not associated with a statistical increase in major airway complications.
  
  
  CONCLUSIONS
  Long duration of ventilation in prone position significantly reduces ICU mortality when only ARDS patients are considered.
authors.affiliation: ICU CHU F, Bourguiba, 1st June 1955 Str, University of Monastir, Monastir 5000, Tunisia. f.abroug@rns.tn
authors.forename: Fekri
authors.initials: F
authors.lastname: Abroug
authors.forename: Lamia
authors.initials: L
authors.lastname: Ouanes-Besbes
authors.forename: Fahmi
authors.initials: F
authors.lastname: Dachraoui
authors.forename: Islem
authors.initials: I
authors.lastname: Ouanes
authors.forename: Laurent
authors.initials: L
authors.lastname: Brochard
mesh_terms: D055371:Acute Lung Injury / Q000401:mortality / Q000628:therapy*; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D056888:Patient Positioning / Q000401:mortality*; D016684:Prone Position; D016032:Randomized Controlled Trials as Topic; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000401:mortality / Q000628:therapy*; D012307:Risk Factors; D016683:Supine Position; D013997:Time Factors; D016896:Treatment Outcome