Statistical analysis
Demographic and clinical characteristics were compared between the treatment groups in a bivariate manner, using Wilcoxon rank-sum tests for continuous variables, due to data skewness, and Chi-Square tests for categorical data, using Fisher’s Exact when expected cell counts were small.
The primary outcome was hospitalization. If a hospitalization occurred within 28 days of an outpatient treatment episode, it was counted as a failure of that treatment. Generalized Estimating Equations (GEE) models were used to determine the association between treatment (AWC alone versus any antibiotics) and hospitalization. Unadjusted and adjusted models were both performed, with the covariates in the multivariable adjusted model being chosen based on their clinical relevance: hospitalization within the past three months of a treatment episode, any prior respiratory culture positive for Pseudomonas aeruginosa , indication for tracheostomy (prematurity, neuromuscular disease and airway obstruction) and time since tracheostomy placement.
All analytic assumptions were verified and analyses were performed using SAS v9.4 (SAS Institute, Cary, NC). This study was approved by Indiana University Institutional Review Board. All data was stored on a REDCap database.