Data synthesis and analysis
Review Manager (RevMan) version 5.3 (Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014) was used to calculate the pooled estimates. Odds ratios (OR) for dichotomous outcomes, the standardized mean difference (SMD) for continuous data and corresponding 95% confidence intervals (CI) were used for the analyses. The I2 statistic was used to evaluate the effect of heterogeneity on the pooled results (I2 > 50% indicated substantial heterogeneity). A fixed-effects model was used to pool data when the heterogeneity was not significant and a random effects model was used when significant heterogeneity was identified. We performed sensitivity analyses of all outcome parameters by adjusting the effects of the models to assess the robustness of the results. We perfomed subgroup analyses by type of study and initial or post-extubation respiratory support. A p -value < 0.05 was considered statistically significant.