Question

Hypoxic pulmonary vasoconstriction is best described as which of the following?

• A. Irreversible pulmonary vasoconstriction due to hypoxia
• B. Reversible pulmonary vasoconstriction due to hypoxia
• C. Directs blood to poorly ventilated areas
• D. Occurs hours after pulmonary vasoconstriction

Hint:

It is an active, reversible response diverting blood away from poorly ventilated lung.

Answer 1

The Correct Option is B

Step 1: Hypoxic pulmonary vasoconstriction (HPV) is an adaptive vasomotor response of the lung to alveolar hypoxia. It involves active constriction of the small muscular resistance pulmonary arteries supplying poorly ventilated alveoli.

Step 2: The purpose of HPV is to redistribute blood flow away from poorly ventilated segments toward better ventilated lung, thereby optimizing ventilation-perfusion matching and oxygenation.

Step 3: A key feature is that HPV is a reversible response: once the alveolar oxygen tension rises again, the vasoconstriction relaxes and blood flow returns. It also begins within seconds to minutes, not hours.

Step 4: Option a is wrong because it is reversible, option c is wrong because blood is diverted AWAY from poorly ventilated areas, and option d is wrong about the time course. The correct description is reversible pulmonary vasoconstriction due to hypoxia.