What physiological change occurs due to Persistent Pulmonary Hypertension (PPHN)?

• A. An increase in systemic blood flow
• B. Reversal of shunt direction
• C. Decreased arterial oxygen saturation
• D. Improved lung compliance

Answer: (B)

Persistent Pulmonary Hypertension (PPHN) is a condition often seen in neonates where there is elevated pressure in the pulmonary arteries leading to reduced blood flow to the lungs. In healthy physiology, blood is directed through the pulmonary vessels to receive oxygen; however, in PPHN, this normal flow is disrupted due to the high pressure.

The correct answer centers on the reversal of shunt direction. Under normal circumstances, blood travels from the right side of the heart to the lungs to become oxygenated before returning to the left side of the heart and subsequently circulating through the body. In PPHN, because of the high pulmonary vascular resistance, a right-to-left shunt can occur through openings like the foramen ovale or ductus arteriosus. This means that deoxygenated blood bypasses the lungs entirely and flows directly to systemic circulation, leading to a decrease in oxygen levels in the blood throughout the body.

This understanding clarifies the physiological disruption caused by PPHN and its impact on the circulatory system of newborns. The other options do not fully capture the primary physiological change associated with PPHN: systemic blood flow typically does not increase (it may actually decrease due to the lack of available oxygen), arterial oxygen saturation decreases