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.