Data Analysis and Power Calculations
Statistical analyses were performed with Stata 16.1 (StataCorp, College Station, TX, USA). Summary data for continuous variables were reported as median with interquartile ranges (IQR) and for categorical variables as numbers with percentages. Continuous data were compared using the Wilcoxon Rank-Sum test and categorical data were compared by Fisher exact test. The associations between AVDSf at onset and echocardiographic findings within the first 24 hours as well as oxygenation metrics were assessed with univariable and multivariable logistic regression. Given the relatively small number of patients with echocardiographic abnormalities, potential confounders were included into the logistic regression model one variable at a time to not overfit the model. Additional analyses included the use of AVDSf as a binary variable based on various cutoffs and the use of RV dysfunction measures as continuous variables. To test the ability of AVDSf to discriminate patients with RV systolic dysfunction or PH, area under the receiver operating curves (AUROC) were calculated. P-values < 0.05 were considered significant for all analyses.
Initial power analysis using the assumptions of abnormal RV GLS rate of 35% in the population and a difference in AVDSf between groups of 0.15 with a standard deviation of 0.2 resulted in a total population of 65 patients required for the study (80% power, alpha = 0.05).