Good News for Lung Repair in Preterm Infants

Abstract

In this issue of the Journal, Narayanan and colleagues (pp. 1104–1109) demonstrated with hyperpolarized helium nuclear magnetic resonance (NMR) (3HeNMR) that the alveolar number and size in preterm infants who had bronchopulmonary dysplasia (BPD) were normal at 10 to 14 years (1). This good news will change how we think about the growth and repair of the injured preterm lung. There is a developmental context for appreciating this new result. The fetal human airways branch about 17 times by about 18 weeks of gestation. A further six generations of airway branching forms the bronchioles and alveolar ducts to yield 500,000 saccules by about 32 to 34 weeks gestation (2). Amazingly, the saccular preterm human lung at 24 weeks gestation can provide gas exchange, and saccular divisions can continue until alveolarization begins. Very preterm lungs also can have altered development from antenatal exposures such as maternal smoking, fetal growth restriction, and chorioamnionitis. The preterm lung is easily injured by mechanical ventilation, oxygen, infection, and probably nutritional deficits despite the best efforts of caretakers. Although survival of these infants has increased strikingly in recent years from advances such as antenatal corticosteroids, postnatal surfactant, and more gentle approaches to mechanical ventilation, the incidence of BPD remains over 40% for infants born at 22 to 28 weeks gestation who survive to 36 weeks gestation (3).