Statistical and power analysis:
SPSS version 25 (SPSS Inc., Chicago, IL) was used to perform the statistical analysis. Data were presented as median with interquartile range or frequencies. Comparison between groups was analyzed by Mann-Whitney U test. Frequencies were analyzed by chi-square test; p values < 0.05 were considered significant. Receiver operator curve (ROC) was constructed and predictive values were calculated. Spearman’s correlation was used to examine correlations of LVEI with PAP.
Power analysis was done comparing extubation trial results. Chi squared test for independent samples was chosen to perform the power analysis, fixing the α-error level at 0.05. Sample size was entered as 100 with success/failure ratio of 67% and 33%. Accordingly, the calculated power was reported to be > 90%.