Patent ductus arteriosus, bronchopulmonary dysplasia and pulmonary hypertension - a complex conundrum with many phenotypes?

The association between patent ductus arteriosus (PDA), bronchopulmonary dysplasia (BPD) and chronic pulmonary hypertension (cPH) in extremely low gestational age neonates (ELGANs) is an area gaining considerable interest. This triad of entities are all intertwined in a complex and multifactorial relationship. PDA can contribute to the development of BPD by increasing pulmonary blood flow, leading to lung injury and inflammation. Additionally, both PDA and BPD can contribute to the development of cPH by increasing pulmonary blood flow and vascular resistance leading to right ventricular dysfunction. The paper by Nawaytou et al., bravely attempts to make sense of it all. The authors attempted to divide PH associated with BPD into a predominantly flow based PH (associated with PDA left to right shunting) and PVR based PH (associated with vascular maladaptive changes). They reported a distinct association between the duration of PDA exposure and the former but not the latter.