Childhood course of lung function in survivors of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the primary respiratory complication of premature birth, and is associated with a reduced maximal lung function. It has been suggested that infants with BPD may carry a risk of a chronic obstructive pulmonary disease–like phenotype developing later in life. However, there is little prospective evidence about the evolution of lung function in long-term survivors of BPD. An Italian group has conducted a prospective study to further investigate the effect of early lung injury on respiratory health during childhood. In total, 17 survivors of BPD, defined as oxygen dependence persisting at 28 days in infants born with a weight less than 1250 g, were evaluated. Maximum flow at functional residual capacity (Vmax_FRC) was measured at 2 years and forced expiratory volume in 1 second (FEV₁) at 9 and 15 years. Two control groups were included in the study: 34 healthy children born at term and 17 children born preterm without BPD. Lung function measurements were compared using z scores. Overall, the BPD group showed consistent lung function tracking, with no significant changes in mean z scores between ages, at 2, 9 and 15 years. No differences in spirometry variables between 9 and 15 years were observed in the control groups. FEV₁ values were significantly lower in the BPD group than in premature non-BPD and term-born children at both 9 and 15 years. Prematurely born non-BPD participants also had lower FEV₁ values than the term-born controls. Among BPD participants, the z scores for Vmax_FRC at 2 years old were correlated with the z scores for FEV₁ (zFEV₁) at 15 years and with the individual differences in zFEV₁ between 9 and 15 years. zFEV₁ declined between 9 and 15 years in BPD survivors with Vmax_FRC less than the 5th percentile at 2 years, but increased in the individuals with greater Vmax_FRC. Moreover, BPD survivors below the 5th percentile had a lower annual rate of FEV₁ growth compared with those above the 5th percentile (160 mL/y vs 245 mL/y; P=0.01) and a significantly lower zFEV₁ at 15 years (-2.77 vs -0.52; P=0.003).
Overall, these results, although still preliminary, confirm that early lung injuries may influence lifetime respiratory health. Moreover, severe early airflow obstruction at 2 years identified survivors of BPD at greater risk of impaired lung growth during their childhood, suggesting a guarded long-term respiratory prognosis. Patients with better airflow at 2 years showed an improvement in lung function in later childhood, thus suggesting some degree of functional recovery. In addition, these findings suggest that preterm delivery without BPD may also affect long-term lung function, although to a lesser extent than in patients with BPD.

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