Hypoxic pulmonary vasoconstriction inhibition — FRCA Primary MCQ

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HardPhysiologyHypoxic pulmonary vasoconstriction inhibitionFRCA Primary

During one-lung ventilation for thoracic surgery, oxygenation worsens after increasing volatile anaesthetic concentration and giving vasodilators. Which physiological mechanism has most likely been impaired?

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Correct answer: C — Hypoxic pulmonary vasoconstriction

Hypoxic pulmonary vasoconstriction diverts blood away from poorly ventilated lung regions and reduces shunt during one-lung ventilation. Volatile agents and vasodilators can inhibit this response, worsening oxygenation. The Haldane and Bohr effects describe haemoglobin carriage of CO2 and oxygen, not regional pulmonary blood flow diversion. Maintaining HPV is particularly important during thoracic anaesthesia.

Reference: West Respiratory Physiology; Nunn's Applied Respiratory Physiology