Very low birth weight (VLBW) infants, even those without bronchopulmonary dysplasia (BPD) are at risk for pulmonary morbidity during infancy. Although some studies have found an association between the level of neonatal oxygen exposure and later morbidity, others have not. A possible explanation for these inconsistent findings is that the cumulative dosage of neonatal supplemental oxygen to which infants are exposure is difficult to accurately quantify.
Methods: A prospective cohort study of VLBW infants without BPD was performed to test the hypothesis that cumulative oxygen exposure in the neonatal period summarized using an area under the curve analysis (Oxygen(AUC)) is predictive of later pulmonary symptoms. Risk factors tested in the analysis included both neonatal and outpatient respiratory exposures. Outcome measures included respiratory symptoms and use of medications and health services to treat those symptoms.
Results: The prevalence of pulmonary symptoms after NICU discharge was 48% (36 of 75 patients). Oxygen(AUC) as early as 72 hr of age predicts respiratory symptoms and respiratory-related health service and medication use during infancy in a dose dependent manner. Oxygen(AUC) is a stronger predictor of later respiratory symptoms than is the number of days of supplemental oxygen or positive pressure respiratory therapy or integrated mean airway pressure (MAP(AUC)).
Conclusions: Oxygen(AUC) as early as 72 hr of age is predictive of later respiratory symptoms and use of health services and medications to treat those symptoms. Supplemental oxygen therapy should be monitored carefully to minimize oxygen exposure and risk of later respiratory symptoms in VLBW infants.