Carol Hodgson, Ewan C Goligher, Meredith E Young, Jennifer L Keating, Anne E Holland, Lorena Romero, Scott J Bradley, David Tuxen

Recruitment manoeuvres involve transient elevations in airway pressure applied during mechanical ventilation to open ('recruit') collapsed lung units and increase the number of alveoli participating in tidal ventilation. Recruitment manoeuvres are often used to treat patients in intensive care who have acute respiratory distress syndrome (ARDS), but the effect of this treatment on clinical outcomes has not been well established. This systematic review is an update of a Cochrane review originally published in 2009. Our primary objective was to determine the effects of recruitment manoeuvres on mortality in adults with acute respiratory distress syndrome.Our secondary objective was to determine, in the same population, the effects of recruitment manoeuvres on oxygenation and adverse events (e.g. rate of barotrauma). For this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCO), Latin American and Caribbean Health Sciences (LILACS) and the International Standard Randomized Controlled Trial Number (ISRCTN) registry from inception to August 2016. We included randomized controlled trials (RCTs) of adults who were mechanically ventilated that compared recruitment manoeuvres versus standard care for patients given a diagnosis of ARDS. Two review authors independently assessed trial quality and extracted data. We contacted study authors for additional information. Ten trials met the inclusion criteria for this review (n = 1658 participants). We found five trials to be at low risk of bias and five to be at moderate risk of bias. Six of the trials included recruitment manoeuvres as part of an open lung ventilation strategy that was different from control ventilation in aspects other than the recruitment manoeuvre (such as mode of ventilation, higher positive end-expiratory pressure (PEEP) titration and lower tidal volume or plateau pressure). Six studies reported mortality outcomes. Pooled data from five trials (1370 participants) showed a reduction in intensive care unit (ICU) mortality (risk ratio (RR) 0.83, 95% confidence interval (CI) 0.72 to 0.97, P = 0.02, low-quality evidence), pooled data from five trials (1450 participants) showed no difference in 28-day mortality (RR 0.86, 95% CI 0.74 to 1.01, P = 0.06, low-quality evidence) and pooled data from four trials (1313 participants) showed no difference in in-hospital mortality (RR 0.88, 95% CI 0.77 to 1.01, P = 0.07, low-quality evidence). Data revealed no differences in risk of barotrauma (RR 1.09, 95% CI 0.78 to 1.53, P = 0.60, seven studies, 1508 participants, moderate-quality evidence). We identified significant clinical heterogeneity in the 10 included trials. Results are based upon the findings of several (five) trials that included an "open lung ventilation strategy", whereby the intervention group differed from the control group in aspects other than the recruitment manoeuvre (including co-interventions such as higher PEEP, different modes of ventilation and higher plateau pressure), making interpretation of the results difficult. A ventilation strategy that included recruitment manoeuvres in participants with ARDS reduced intensive care unit mortality without increasing the risk of barotrauma but had no effect on 28-day and hospital mortality. We downgraded the quality of the evidence to low, as most of the included trials provided co-interventions as part of an open lung ventilation strategy, and this might have influenced results of the outcome.