Discussion
The burden of respiratory morbidities in children with BPD can be lifelong 13 and identifying those at highest risk for long-term respiratory morbidities, is challenging. Children with BPD who require supplemental oxygen at initial hospital discharge have varying degrees of cardiopulmonary involvement and are likely at higher risk for chronic respiratory symptoms during the pre-school years when compared to children discharged off supplemental oxygen.14Identifying factors that predict outpatient acute care usage, chronic respiratory symptoms and timing to oxygen liberation could help modify respiratory morbidities in these children . This study focused on children with BPD discharged to home on supplemental oxygen to address these issues. Not unexpectantly, children discharged on higher levels of supplemental oxygen were more likely to have severe BPD and to carry the diagnosis of pulmonary hypertension. Additionally, those who required higher levels of supplemental oxygen at initial hospital discharge were more likely to have lower birthweight percentiles and to be older at initial hospital discharge. However, children discharged on higher levels of supplemental oxygen did not have a higher likelihood of acute care usage, chronic respiratory symptoms or need for respiratory medications during acute illnesses when compared to those discharged on lower levels of supplemental oxygen. The likelihood of weaning supplemental oxygen, in a given month, was significantly lower in children with gastrostomy tubes, children prescribed inhaled corticosteroids and in those who lived in homes with lower estimated incomes. Findings from this study suggest that although severity of BPD influences level of supplemental oxygen at initial hospital discharge, other factors after hospital discharge influence weaning of supplemental oxygen and respiratory morbidities, including socioeconomic status (SES) and ICS use, which could be modifiable factors.
In this study, several risk factors were associated with delayed weaning of supplemental oxygen. In particular, we found that weaning oxygen, per given month was less likely in children with lower estimated household incomes. This finding suggest that socioeconomic status can be a factor in liberating a child from supplemental oxygen in the outpatient setting. This finding raises the question of whether children with lower SES, have more difficulties in accessing care, once they are in the outpatient setting. However, a recent study did not support this.15 Additional studies will be needed to determine if other health disparities or perceptions due to SES, influence variations in oxygen weaning strategies in children with BPD. We also found that higher use of ICS was associated with delayed weaning of supplemental oxygen. It is possible that ICS was used as an additive therapy in those who were more difficult to wean from supplemental oxygen, which may account for delayed weaning of supplemental oxygen. Other reasons may also affect weaning in the outpatient setting. Wong et. al., studied infants with moderate or severe BPD discharged on varying amounts of supplemental oxygen. They found that shorter NICU stays were associated with quicker oxygen weans at 9 and 12 months with no correlation to birthweight or gestational age.16Our findings indicate that factors after initial hospital discharge can influence weaning of supplemental oxygen in children with BPD.
In this study, no differences in acute care usage or respiratory symptoms were found between any of the oxygen groups in children with BPD. Higher levels of supplemental oxygen at discharge were not associated with increased rates of emergency room visits, hospitalizations, systemic steroid use, or antibiotic use for respiratory conditions. There were also no differences in chronic respiratory symptoms or rescue medication use between the oxygen groups. It is possible that supplemental oxygen use in the outpatient setting lowers hospitalizations in BPD children by mitigating hypoxemia that can occur during acute respiratory illnesses, regardless of amount given. Greenough et. al., reported that children with BPD between the ages of 2 to 4 years who required supplemental oxygen did not have increased hospital admissions, compared to those on room air. 9However, their study did see an increase in wheezing and use of inhalers. Lodha et. al., 10 also examined respiratory outcomes at 3 years of age in children without BPD, with BPD, and with BPD on supplemental oxygen. They reported that children with BPD on supplemental oxygen did not have higher rates of hospitalization or antibiotic use compared to the other groups. Unlike our study however, Lodha et. al., did not stratify by amount of supplemental oxygen use. Other studies however, have shown higher rates of rehospitalization for respiratory issues in infants with BPD requiring oxygen supplementation at home.8,16 Our study suggest that being on any level of supplemental oxygen at initial discharge, could provide a buffer to support adequate oxygen levels during periods of illness, lessening the likelihood of hospitalization in children with more severe BPD.
A limitation of this study is the retrospective nature of the study design. Furthermore, this study included patients from two centers, in which the demographics of these cohorts predominately represent an urban population, which may not be generalizable to other patient populations, particularly those in rural areas. Additionally, both centers in this study have outpatient BPD clinics which may account for higher comfort in discharging children with BPD on higher levels of oxygen in the outpatient setting. Nevertheless, our study results suggest that the use of supplemental oxygen can help to mitigate differences in BPD severity with regard to acute care usage and reported respiratory symptoms in children with BPD in the outpatient setting.
In summary, among BPD children on supplemental oxygen in the outpatient setting, the level of oxygen supplementation at initial hospital discharge was not shown to correlate with acute care usage or respiratory symptoms. Weaning of supplemental O2 however was significantly associated with household income and ICS use, indicating that these factors can influence timing of oxygen weaning by healthcare providers in the outpatient setting.
Table 1: Demographic and Clinical Characteristics by Oxygen Amount at Initial Hospital Discharge