Lung function development after preterm birth in relation to severity of Bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a strong risk factor for respiratory morbidity in children born preterm. Our aims were to evaluate lung function in adolescents born preterm with and without a history of BPD, and to assess lung function change over time from school age.

Fifty-one individuals born in Stockholm, Sweden between gestational ages 24 to 31 weeks (23 neonatally diagnosed with respiratory distress syndrome (RDS) but not BPD, and 28 graded as mild (n = 17), moderate (n = 7) or severe (n = 4) BPD) were examined in adolescence (13-17 years of age) using spirometry, impulse oscillometry (IOS), plethysmography, and ergospirometry. Comparison with lung function data from school age (6-8 years of age) was also performed.

Adolescents with a history of BPD had lower forced expiratory volume in 1 s (FEV₁) compared to those without BPD (-0.61 vs.-0.02 z-scores, P < 0.05), with lower FEV₁ values significantly associated with BPD severity (P for trend 0.002). Subjects with severe BPD had higher frequency dependence of resistance, R_5-20, (P < 0.001 vs. non-BPD subjects) which is an IOS indicator of peripheral airway involvement. Between school age and adolescence, FEV₁/FVC z-scores decreased in all groups and particularly in the severe BPD group (from -1.68 z-scores at 6-8 years to -2.74 z-scores at 13-17 years, p < 0.05 compared to the non-BPD group).

Our results of spirometry and IOS measures in the BPD groups compared to the non-BPD group suggest airway obstruction including involvement of peripheral airways. The longitudinal result of a decrease in FEV₁/FVC in the group with severe BPD might implicate a route towards chronic airway obstruction in adulthood.