Premature birth affects the degree of airway dysanapsis and mechanical ventilatory constraints

Abstract

Adult survivors of very preterm birth (≤32 weeks gestational age) without (PRE) and with bronchopulmonary dysplasia (BPD) have obstructive lung disease as evidenced by reduced expiratory airflow at rest and have significant mechanical ventilatory constraints during exercise. Airflow obstruction, under any condition, could be due to several factors including small airways. PRE and/or BPD could have smaller airways than their counterparts born at full-term (CON) due to a greater degree of dysanaptic airway development during the pre- and/or post-natal period. Thus, the purpose of the present study was to compare the dysanapsis ratio (DR), as an index of airway size, between PRE, BPD, and CON. To do so, we calculated DR in PRE (n = 21), BPD (n = 14) and CON (n = 34) individuals, as well as examined flow-volume loops at rest and during sub-maximal exercise. DR, using multiple estimates of static recoil pressure, was significantly smaller in PRE and BPD (0.16 ± 0.05 and 0.10 ± 0.03 AU) compared to CON (0.22 ± 0.04 AU; both P < 0.001) and smallest in BPD (P < 0.001). DR was significantly correlated to peak expiratory airflow at rest (r = 0.42; P < 0.001) and the extent of expiratory flow limitation during exercise (r = 0.60; P < 0.001). Our findings suggest that PRE/BPD may have anatomically smaller airways than CON, which may help explain their lower expiratory airflow rate at rest and during exercise and further our understanding of the consequences of preterm birth and neonatal O₂ therapy.

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