Which is a physiologic effect of inhaled nitric oxide?

Which is a physiologic effect of inhaled nitric oxide?

• A. Increases systemic vascular resistance
• B. Decreases oxygenation
• C. Increases PAP
• D. Relaxes smooth muscle in pulmonary vasculature

Answer: (D)

Inhaled nitric oxide acts as a selective pulmonary vasodilator by diffusing into vascular smooth muscle and increasing cGMP, which relaxes the smooth muscle in the pulmonary arterioles. This lowers pulmonary vascular resistance and pulmonary artery pressure, improving blood flow to well-ventilated regions of the lung and thereby enhancing oxygenation. Because NO is rapidly inactivated by hemoglobin, its effects are largely confined to the lungs with minimal impact on systemic vascular resistance. The other options describe effects opposite to NO’s action or incorrect outcomes (NO does not increase systemic resistance, worsen oxygenation, or raise pulmonary artery pressure). In practice, this agent is used to treat conditions like PPHN, with monitoring for methemoglobinemia and NO2.

Inhaled nitric oxide acts as a selective pulmonary vasodilator by diffusing into vascular smooth muscle and increasing cGMP, which relaxes the smooth muscle in the pulmonary arterioles. This lowers pulmonary vascular resistance and pulmonary artery pressure, improving blood flow to well-ventilated regions of the lung and thereby enhancing oxygenation. Because NO is rapidly inactivated by hemoglobin, its effects are largely confined to the lungs with minimal impact on systemic vascular resistance. The other options describe effects opposite to NO’s action or incorrect outcomes (NO does not increase systemic resistance, worsen oxygenation, or raise pulmonary artery pressure). In practice, this agent is used to treat conditions like PPHN, with monitoring for methemoglobinemia and NO2.