Exposure to oxygen and head growth in infants with bronchopulmonary dysplasia

Infants with bronchopulmonary dysplasia (BPD) are known to have developmental delays, but a direct link between oxygen (O (2)) exposure and brain growth has not been explored. Our objective was to test the hypothesis that the use of O (2) is associated with delays in head growth (DHG) in premature infants with BPD. We conducted a retrospective study on a cohort of infants with BPD (birthweight [BW] < 1500 g, gestational age < 34 weeks). The study population was divided into two groups based on their head circumference (HC) measured at birth. Group 1 represented infants with birth HC > or = 50% for their age on growth chart, and Group 2 represented infants with birth HC < 50% for their age. We recorded HC at hospital discharge and at 6 months of age; and the amount of DHG was calculated (DHG = current age in weeks - the age that matches the 50th percentile for current HC). Regression analysis was conducted to determine the relationship between the duration of O (2) use and DHG in both groups, controlling for BW, discharge weight, gender, and duration of mechanical ventilation (MV). Data were expressed in mean +/- standard error of mean. A total of 137 sequential infants with BPD were studied; of them 65 infants were included in group 1 and 72 infants were included in group 2. The 2 groups did not differ in GA, gender total O (2) days, and total days on MV. At hospital discharge there was no difference between groups in terms of DHG (78% versus 83%, respectively). At 6 months of age, there were more infants in group 2 who had DHG (44% versus 67%, respectively; P < 0.01). In group 1, the amount of DHG correlated only with BW ( P = 0.05). It did not correlate with discharge weight, gender, duration of O (2) use, or duration of MV. In group 2, the amount of DHG correlated only with the duration of O (2) use ( P = 0.04) It did not correlate with BW, discharge weight, gender, or duration of MV. Each 10 days of O (2) use in group 2 was associated with 1.5 +/- 0.1 days of DHG. We concluded that duration of O (2) use is associated with a delay in head growth in infants born with HC < 50th percentile. This study does not clarify whether the use of O (2) is a marker of severity of illness or a contributing factor to DHG in infants with BPD. The mechanisms for this relation require further exploration.