Bronchodilator response
Consistent with the findings in other studies18,21,23,27, the EP adolescents with BPD in our study showed a greater bronchodilator response than those without BPD after adjusting for potential confounders. In addition, studies also found that EP children and adolescents had a greater bronchodilator response than full-term controls18,21. However, we only found positive bronchodilator test results in 16% of the adolescents with history of BPD.
A lack of correlation between the degree of bronchial hyperresponsiveness and atopy and normal levels of exhaled nitric oxide has been documented in EP children and adolescents18,28. Therefore, it is thought that EP children and adolescents have no eosinophilic airway inflammation, as observed in typical asthma patients. Instead, airway obstruction might be related to structural changes due to immaturity and perinatal pulmonary damage induced by ventilation and prolonged use of oxygen. Over time, these changes could lead to fixed or irreversible airflow obstruction, which would explain the low rate of positive results in the bronchodilator test in our study, as reported by other studies18,21,28. Thus, BPD and asthma share some similarities in clinical manifestations and lung function, although they differ in the pathogenesis of bronchial obstruction.