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.