Longitudinal lung function in school-age children born very preterm

Abstract

Introduction: Bronchopulmonary dysplasia (BPD) remains the most significant pulmonary complication of preterm birth. The long term respiratory sequelae of children born very preterm are unclear.

Aim: To examine how lung function tracks over the school years in children born very preterm.

Methods: Term controls (N=32) and children born <32 weeks gestational age (GA) with (+BPD, N=74) and without (−BPD, N=44) a neonatal classification of BPD performed lung function at 4-7 and/or 9-11 years. Outcomes from spirometry (FEV1, FVC, FEV1/FVC, FEF25-75%) and the forced oscillation technique (area under reactance curve (AX), respiratory system resistance (R) and reactance (X) at 8 Hz)) were expressed as Z-scores. Paired t-test and Fisher's exact test were used to assess change in lung function and change in the proportion of children with lung function outside normal limits (1.64 Z-scores) between visits.

Results: Compared to term controls, children born preterm had lower lung function at both visits by spirometry (FEV1, FEV1/FVC, FEF25-75) and the FOT (AX, Fres, X8) regardless of BPD classification (P<0.05).

Longitudinal data (15 term; 39+BPD; 29-BPD) showed a decline (mean Z-score difference ± SD) in FEV1 (−0.47 ± 0.92; P=0.011) and FEF25-75% (−0.61 ± 0.76; P=0.001) for the +BPD group and an increased proportion of children with abnormal FEV1/FVC (32% to 52%) and FEF25-75% from (32% to 68%) between the two visits. In contrast, AX and X8 showed improvement over time in both preterm groups, though the proportion of children outside the normal limit was not different between the two time points.

Conclusion: Children born <32 weeks GA with BPD experience lung function decline during childhood which may warrant intervention.