Patterns of respiratory disease during the first 2 postnatal weeks in extremely premature infants

Pulmonary disease among infants of <28 weeks' gestation (extremely low gestational age newborns) often has the following pattern: the infant starts out with little need for supplemental oxygen and ventilatory support in the first postnatal week but then has pulmonary deterioration in the second postnatal week, with an increased need for supplemental oxygen and respiratory support. We evaluated the antecedents and correlates of patterns of early lung disease, with particular emphasis on pulmonary deterioration, in a large cohort study (the Extremely Low Gestational Age Newborn [ELGAN] study).

We examined data collected prospectively on 1340 infants born between 2002 and 2004 at 23 to 27 completed weeks of gestation and who survived to 14 days. Pulmonary deterioration was defined as receipt of fraction of inspired oxygen < 0.23 on any day between days 3 and 7 and receipt of fraction of inspired oxygen > or = 0.25 on day 14.

One fifth (20%) of the infants had consistently low fraction of inspired oxygen, approximately two fifths (38%) had pulmonary deterioration, and the remaining approximately two fifths (43%) had consistently high fraction of inspired oxygen (early and persistent lung dysfunction). Compared with infants who had consistently low fraction of inspired oxygen, infants who experienced pulmonary deterioration had lower gestational ages and lower birth weights, had higher scores for neonatal acute physiology, and received more intensive modes of respiratory support. Gender, multifetal pregnancy, cesarean delivery, antenatal steroids, chorioamnionitis, and funisitis were not associated with pulmonary deterioration. The incidence of chronic lung disease, defined as oxygen therapy at 36 weeks' postmenstrual age, was 17% in the consistently low fraction of inspired oxygen group, 51% in the pulmonary deterioration group, and 67% in the early and persistent pulmonary dysfunction group. The incidence of death in these 3 groups before 36 weeks' postmenstrual age was 1%, 3%, and 5%, respectively.

Nearly 40% of extremely low gestational age newborns experience pulmonary deterioration in the first 2 postnatal weeks, and half of these infants develop chronic lung disease. Indicators of developmental immaturity and illness severity were associated with both pulmonary deterioration and chronic lung disease. Studying the antecedents of pulmonary deterioration might provide new insights about chronic lung disease pathogenesis.