Methods
Study Population: Children with the diagnosis of BPD and seen in the Children’s Hospital of Philadelphia outpatient pulmonary clinics between 2016-2021 were identified using electronic medical records (EMR). Inclusion criteria included birth prior to 34 weeks gestational age, a diagnosis of BPD by the 2001 National Heart, Lung, and Blood Institute (NHLBI) consensus statement, (13) and being 8 years of age or less at their first pulmonary clinic visit. Those who had tracheostomies and/or were ventilator-dependent were excluded. Inhaled corticosteroid (ICS) use and timing of initiation were determined by chart review. History of pulmonary hypertension was determined by chart review. Outcomes included asthma diagnosis and acute care usage before and after their first pulmonary visit. This study was approved by the Children’s Hospital of Philadelphia Institutional Review Board (IRB# 20-017614) under exempt research. ICD-10 codes were used to identify children with the diagnosis of BPD with or without the diagnosis of asthma. These ICD codes were: P27.1, P27.1 + J45, P27.9 and P27.9 + J45.
Statistics: Descriptive means and frequencies were compared using t tests and chi square tests, respectively (Tables 1 and 3 and Supplemental Tables 1-3). Odds ratios for admissions and visits were derived from logistic regressions adjusted for potential confounders that were selected a priori , including gestational age, birth weight, supplemental oxygen use at NICU discharge, and duration of follow-up time (i.e., either time between NICU discharge and first pulmonary visit or time between first pulmonary visit and time of chart review) (Table 4). The odds ratio for a diagnosis of asthma was derived similarly, except age at last follow-up was substituted for duration of follow-up time. Kaplan-Meier analyses were used to assess differences between groups for time until the diagnosis of asthma (Figure 1). Stata IC 15 (StataCorp, LLC; College Station, TX) was used for all analyses. P values of less than 0.05 were defined as significant.