skip to main content

Hypoxic pulmonary vasoconstriction during one-lung ventilation — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

HardPhysiologyHypoxic pulmonary vasoconstriction during one-lung ventilationFRCA Primary

During one-lung ventilation for thoracic surgery, a patient's SpO2 falls from 96% to 88%. FiO2 is 1.0, the non-dependent lung is not ventilated, and a high concentration volatile anaesthetic is being used. What physiological mechanism most likely worsens oxygenation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Inhibition of hypoxic pulmonary vasoconstriction increasing perfusion of the non-ventilated lung

Hypoxic pulmonary vasoconstriction diverts blood away from poorly ventilated lung regions; inhibition increases shunt through the non-ventilated lung during one-lung ventilation. FiO2 is already 1.0, so the key issue is perfusion of non-ventilated alveoli rather than inspired oxygen fraction. Increased shunt is the dominant mechanism of desaturation. The pearl is that anaesthetic technique and pulmonary vascular tone can affect oxygenation during one-lung ventilation.

Reference: RCoA Primary FRCA Syllabus 2026; Ganong's Review of Medical Physiology; West's Respiratory Physiology