What physiological changes are associated with PPHN?

Persistent pulmonary hypertension of the newborn (PPHN) is characterized by elevated pulmonary vascular resistance (PVR) relative to systemic vascular resistance (SVR). In this condition, the high PVR leads to inadequate blood flow through the pulmonary circulation, resulting in decreased oxygenation and other oxygenation-related complications.

In PPHN, the right-to-left shunting of blood occurs through the foramen ovale and ductus arteriosus due to the high pressure in the pulmonary circulation compared to the systemic circulation. This physiological change reflects that PVR exceeds SVR, demonstrating the failure of the transition to normal neonatal circulation, whereby PVR decreases significantly after birth.

The significance of this imbalance is critical for understanding the management and treatment options for PPHN, which may include therapy aimed at reducing PVR, such as inhaled nitric oxide or other interventions designed to improve oxygenation and hemodynamics in the affected neonate. Overall, recognizing the relationship between PVR and SVR is essential in diagnosing and managing PPHN effectively.