Bronchopulmonary dysplasia increases the risk of disability in extremely preterm infants. Although the pathophysiology remains uncertain, prior exposure to intermittent hypoxemia may play a role in this relationship.
To determine the association between prolonged episodes of intermittent hypoxemia and severe bronchopulmonary dysplasia.
Post-hoc analysis of extremely preterm infants in the Canadian Oxygen Trial who survived to 36 weeks postmenstrual age. Oxygen saturations <80% for ≥1 minute and the proportion of time per day with hypoxemia were quantified using continuous pulse oximetry data that had been sampled every 10 seconds from within 24 hours of birth until 36 weeks postmenstrual age. The study outcome was severe bronchopulmonary dysplasia as defined in the 2001 National Institutes of Health Workshop Summary.
Of 1018 infants, 332 (32.6%) developed severe bronchopulmonary dysplasia. The median number of hypoxemic episodes ranged from 0.8/day (IRQ 0.2-1.1) to 60.2/day (IQR 51.4-70.3) among the least and most affected 10% of infants. Compared to the lowest decile of exposure to hypoxemic episodes, the adjusted relative risk of severe bronchopulmonary dysplasia increased progressively from 1.72 (95% CI 1.55-1.90) at the second decile to 20.40 (95% CI 12.88-32.32) at the 10th decile. Similar risk gradients were observed for time in hypoxemia. Significant differences in the rates of hypoxemia between infants with and without severe bronchopulmonary dysplasia emerged within the first week after birth.
Prolonged intermittent hypoxemia beginning in the first week after birth was associated with an increased risk of developing severe bronchopulmonary dysplasia among extremely preterm infants.