Predictors and Outcomes 
We determined 3 predictor groups based on dichotomous bacterial identification. Inpatient, outpatient, and laboratory-collected cultures were included to define these categories. The group of children with “any pathogen identified” was defined as those with identification of at least 1 pathogenic organism on any respiratory culture obtained in the first 3 years following tracheostomy placement (inclusive ofP. aeruginosa, Figure 1a ). The group of “any P. aeruginosa identified” was defined as children with identification ofP. aeruginosa specifically on at least one respiratory culture in this timeframe. The group of “chronic P. aeruginosa identified” was defined as the subgroup of children with isolation of P. aeruginosa in > 50% of cultures obtained in any continuous 12-month period in the 3 years post-tracheostomy placement using an adaptation to previously-described criteria.20 To evaluate the effect of repeated organism growth events, each child’s count of cultures with pathogenic organisms and count of cultures with P. aeruginosa during the 3 years of enrollment post-tracheostomy were summarized as additional predictor variables.
“Pathogenic organisms” were defined a priori according to CCHMC microbiology lab guidelines as organism types and quantities not expected in oropharyngeal flora, including but not limited toPseudomonas aeruginosa, Staphylococcus aureus, andKlebsiella pneumoniae, as previously described.21 Cultures with no speciated organisms or only “oropharyngeal flora” were categorized as “negative”. The CCHMC microbiology lab defines oropharyngeal flora broadly, to includeHaemophilus species, Streptococcus pneumoniae ,Staphylococcus aureus , and Moraxella catarrhalis when isolated in small numbers with other oropharyngeal flora. This microbiology lab does not have specimen rejection criteria.
The primary outcome was the alive child’s continued use of respiratory support at 3 years post-tracheostomy placement. Respiratory support use was defined dichotomously as the use of any of the following: supplemental oxygen, high flow nasal cannula, continuous positive airway pressure(CPAP), bilevel positive airway pressure(BiPAP), or mechanical ventilation at baseline when well for any portion of the day or night. Secondary outcomes examined were decannulation status at 3 years post-tracheostomy placement and death by 3 years post-placement.