Abstract
OBJECTIVES: To evaluate whether preterm birth is associated with impaired airway and parenchymal lung function and whether early physiological phenotypes change or are sustained during follow-up during infancy. STUDY DESIGN: We included125 infants born preterm who underwent forced expiratory flow at 75% (FEF(75)), expired forced vital capacity, lung diffusion (D(L)), and alveolar volume measured longitudinally after discharge from the neonatal intensive care unit. RESULTS: The average gestational age of the cohort was 31 weeks (range, 25-36), 52% were female, and 36% were diagnosed with bronchopulmonary dysplasia. Length and lung function were evaluated at mean corrected ages of 5.4 and 13.6 months, visit 1 and visit 2, respectively. Significant increases occurred in body length (11.82 cm), FEF(75) (94.3 mL/s), forced vital capacity (149 mL), D(L) (147 mL/min/mm Hg), and alveolar volume (254 mL) (P < .01 for each parameter). When quantified by z-scores based on full-term infants, the Δz-length increased significantly (P < .01); however, there were significant decreases in Δz-FEF(75) and Δz-D(L) (P < .01). Lower FEF(75) and D(L) values at visit 1 were associated with lower values at visit 2, but were not associated with gestational age or bronchopulmonary dysplasia. CONCLUSIONS: After preterm birth, absolute values for lung function increased during infancy; however, when expressed as z-scores, values were persistently impaired and became more negative relative to full-term infants. Airway and parenchymal function may be established early after preterm birth and may contribute to impaired trajectories or dysanapsis later in life.