The advances in obstetric and neonatal care over the last half century have resulted in changes in pathophysiology and clinical presentation of bronchopulmonary dysplasia (BPD). In contrast to the original description of BPD by Northway et al as a severe lung injury in relatively mature preterm infants, the most common form of BPD currently is characterized by chronic respiratory insufficiency in extremely preterm infants. This evolution in the presentation of BPD, along with changes in respiratory support strategies such as increased use of nasal cannula oxygen, has presented a unique challenge to find a definition that describes the severity of lung damage and predict the long-term respiratory outcomes with some accuracy.
The limitations of current definitions of BPD include inconsistent correlation with long-term respiratory outcomes, inability to classify infants dying from severe respiratory failure prior to 36 weeks' postmenstrual age, and potential inappropriate categorization of infants on nasal cannula oxygen or with extrapulmonary causes of respiratory failure. In the long term, the aim for a new definition of BPD is to develop a classification based on the pathophysiology and objective lung function evaluation providing a more accurate assessment for individual patients. Until then, a consensus definition that encompasses current clinical practices, provides reasonable prediction of later respiratory outcomes, and is relatively simple to use should be achieved.