skip to main content

West Zones — FRCA Primary MCQ

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

HardPhysiology - RespiratoryWest ZonesFRCA Primary

An upright, spontaneously breathing patient has a regional alveolus in West zone 2. A modest increase in alveolar pressure occurs with no change in pulmonary arterial or venous pressures. Which statement best predicts regional flow?

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

Reveal the answer and explanation

Correct answer: C — Flow falls because the arterial-to-alveolar pressure gradient narrows

The best answer is “Flow falls because the arterial-to-alveolar pressure gradient narrows”. In zone 2, pulmonary arterial pressure exceeds alveolar pressure, which exceeds pulmonary venous pressure. Flow is therefore governed by arterial minus alveolar pressure; raising alveolar pressure narrows that gradient. Venous pressure does not set flow while it remains below alveolar pressure. Complete cessation would require alveolar pressure to reach or exceed arterial pressure, the zone-1 relationship.

Reference: RCoA, Primary FRCA syllabus: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf; Lung circulation review: https://pmc.ncbi.nlm.nih.gov/articles/PMC7432532/