skip to main content

RV Cannot Be Measured by Spirometry — FRCA Primary MCQ

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

EasyPhysiology - RespiratoryRV Cannot Be Measured by SpirometryFRCA Primary

Regarding the measurement of residual volume (RV) it cannot be measured by spirometry because:

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

Reveal the answer and explanation

Correct answer: A — RV is the volume remaining in the lungs after maximal expiration and cannot be exhaled

RV is the volume of gas remaining in the lungs after maximal forced expiration (~1.2 L in adults). It cannot be exhaled therefore cannot be measured by spirometry (which measures exhaled volumes). It is measured by: body plethysmography (Boyle's law) / helium dilution (closed circuit) / or nitrogen washout (open circuit).

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist