Methods
This was a secondary cohort analysis of infants born <32 weeks gestational age with BPD discharged with home oxygen from 2015-2018. Infants were either discharged from our level IV NICU or regional level III NICUs and referred to our pulmonary clinic after NICU discharge for home oxygen management. BPD was defined as respiratory support at 36 weeks post-menstrual age.7-9 Infants with tracheostomies and surgical non-respiratory comorbidities were excluded; only one member of a multiple gestation was included. For the larger prospective observational cohort study in our NICU caregivers were consented. The infants referred to our pulmonary clinic were considered exempt as a retrospective chart review.
Infants in our BPD clinic are seen 4-6 weeks after discharge from the NICU. Home oxygen is weaned using a structured algorithm, which has been previously published. 7 We also have a standardized guideline for the management of diuretics. Diuretic medications are either actively or passively weaned (Figure 1). We start active diuretic weaning during the first BPD clinic visit if the infant had a pre-discharge pCO2 less than 60 mmHg, no cardiac abnormalities, gaining weight appropriately and passes a room air trial in clinic. If the infant is on a therapeutic dose, we decrease the dose from twice a day to daily one week before the next clinic visit and discontinue at that visit if the infant is clinically stable. If the infant is on a subtherapeutic dose, we decrease the dose to daily at the first visit and tell the parents to discontinue a week before the next visit. Passively weaned means we allow the infant to gradually outgrow their dose. Weaning diuretics and home oxygen occur at the same time.
Our primary exposure variable of interest was diuretic weaning strategy. To test our primary hypothesis that active weaning of diuretics does not prolong duration of home oxygen therapy or trigger unexpected visits, we defined three groups: those discharged from the NICU without diuretics, those actively weaned from diuretics, and those who were passively weaned from diuretics without high-risk indications including patent ductus arteriosus, pulmonary hypertension on echocardiogram after 36 weeks corrected age, or other illness related reason. Infants passively weaned due to high-risk indications were excluded for this analysis.
Our primary outcome was duration of home oxygen in weeks after NICU discharge. Discontinuation of home oxygen was defined as passing a home overnight pulse oximetry study on room air, determined by manual chart review. Secondary outcomes included number of failed room air trials in clinic, overnight pulse oximetry trials, oxygen weaned off-protocol, need for sleep study, increased home oxygen above baseline and new or increased diuretics during emergency department, inpatient and clinic encounters, number of visits to BPD clinic and number of missed clinic visits. Off-protocol weaning included infants whose parents started room air trials, advanced room air trials quicker than instructed or took the infant off supplemental oxygen completely. This includes those who were ultimately told to continue the process they started and those that were told to go back to the original plan.
We reviewed charts for NICU illness variables including gestational age at birth, sex, birth weight, multiple gestation, antenatal steroids, surfactant, patent ductus arteriosus (PDA) ligation or medical therapy; number of days requiring ventilation, home oxygen liter flow at discharge, corrected gestational age at discharge, family history of asthma, and discharge with diuretics, bronchodilators, or inhaled corticosteroids. After NICU discharge we reviewed the chart for illness characteristics that might have affected decision-making regarding diuretic or oxygen weaning, which included emergency department visits, readmissions, pediatric intensive care admission, or receipt of systemic corticosteroids. Because inhaled corticosteroids are also frequently used in infants with BPD discharged with home oxygen therapy, both prescribed before and after NICU discharge, we categorized use of inhaled corticosteroids in three groups: no inhaled corticosteroids, prescribed at NICU discharge, and started after NICU discharge.