Post-natal corticosteroids are associated with reduced expiratory flows in children born very preterm.

AIM: Infants born very prematurely often received corticosteroids to minimise the risk of developing bronchopulmonary dysplasia (BPD) but their long term impact on lung function at school age is unclear. METHODS: A cross-sectional study of 105 children [mean gestation of 27 weeks] was undertaken. Lung function assessments were conducted at a mean age of 10 years according to standard criteria. Corticosteroid dose was obtained from the medical record. RESULTS: Spirometry in the BPD group was not significantly different to the non-BPD group, mean per-cent predicted (95% confidence interval) forced expiratory volume in 1 s (FEV1) 83% (79, 87) versus 86% (83, 90), FEF25%-75% 67% (60, 73) versus 75% (69, 81). Antenatal steroid treatment alone did not adversely affect airflow FEV1, 88% (84.92) versus 90% (82.97), and forced expiratory flow (FEF)25%-75%, 75% (69.81) versus 87% (70.104). Children who received post-natal corticosteroids had significantly lower flows than those who did not (FEV1 82% (78.85) vs. 88% (85.92), P = 0.006; FEF25%-75% 65% (59.71) vs. 78% (72.84), P = 0.003). Regression analysis revealed days on oxygen and days ventilated were statistically significant but weak predictors of airflow at 10 years of age. CONCLUSIONS: A diagnosis of BPD did not predict reduced spirometry in middle childhood. Children who received post-natal corticosteroids as preterm infants had reduced expiratory flows compared with those who did not. While post-natal corticosteroids may be a marker of severity of lung disease, the potential of post-natal corticosteroids to influence lung development requires further investigation.

Normal development of the lung and premature birth.

The following review focuses on the normal development of the lung from conception to birth. The defined periods of lung development-Embryonic, Pseudoglandular, Canalicular, Saccular and Alveolar-will be explored in detail in relation to gestational age. Cellular differentiation, formation of the conducting airways and respiratory zone and development of the alveoli will be reviewed. Pulmonary vascular development will also be examined within these periods to relate the formation of the blood-air barrier to the lungs for their essential function of gas exchange after birth. The development of the surfactant and cortisol systems will also be discussed as these need to be mature before the lungs are able to take on their role of respiration following birth. It is clear that premature birth interrupts normal lung development so the effect of preterm birth on lung development will be examined and the respiratory consequences of very preterm birth will be briefly explored.