Differential Trajectories of Airway and Parenchymal Function in Infants Born Preterm

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.

We included125 infants born preterm who underwent forced expiratory flow at 75% (FEF₇₅), expired forced vital capacity, lung diffusion (D_L), and alveolar volume measured longitudinally after discharge from the neonatal intensive care unit.

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), FEF₇₅ (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-FEF₇₅ and Δz-D_L (P < .01). Lower FEF₇₅ 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.

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.