Bronchopulmonary dysplasia (BPD) is the most common form of chronic lung disease in infancy. The clinical, radiological, and pathological features of BPD were first described a little more than three decades ago.1 The disease was then seen in large preterm infants with severe respiratory distress syndrome who had been treated with high inspired oxygen concentrations and prolonged mechanical ventilation with high positive airway pressures resulting in inflammation, fibrosis, and smooth muscle hypertrophy in the airways.2 Despite advances in the prevention and management of respiratory distress syndrome (including the widespread use of antenatal steroids and surfactant treatment), neonatal chronic lung disease is still one of the major complications in mechanically ventilated premature infants. Acceptance of modest hypercapnia with less aggressive application of positive pressure ventilation and reduction of the use of high oxygen concentrations led to a decrease in the incidence of BPD in newborn infants with a birth weight above 1500 g. However, with increased survival of extremely premature infants (24–26 weeks gestation, birth weight <1000 g), who are most likely to develop BPD, the overall incidence has remained high or has even increased, albeit with wide variations between institutions.3-10 Clearly, the risk of developing BPD increases with decreasing birth weight and gestational age, ranging from 50% in neonates with birth weights of 700–900 g to 5% in those with birth weights >1250 g.3 Apart from differences in patient populations and management, the reported variation in the incidence of BPD might also be due to the use of different criteria to define it.1 ,11 ,12

“Classic” BPD, as described by Northway and colleagues, is a severe form of chronic lung disease that has become less common and has been replaced by less severe forms which are observed in very small premature infants who survive after prolonged mechanical …