Desflurane Vaporiser — FRCA Primary MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: A — A boiling point close to room temperature and high saturated vapour pressure require a heated, thermostatically controlled, pressurised vapour circuit
Desflurane boils at 22.8°C and therefore has a saturated vapour pressure close to atmospheric pressure at ordinary theatre temperatures. Output from a conventional variable-bypass vaporiser would consequently be difficult to control, with a risk of boiling and marked temperature-dependent variation. The Tec 6 instead heats desflurane to a controlled temperature and generates pressurised vapour in a separate circuit, which is metered and blended with the fresh gas. Option D reverses desflurane’s physical properties. Option B incorrectly describes it as poorly volatile. A wick and temperature-compensated bypass chamber are features of conventional agent-specific vaporisers, making D incorrect. Desflurane can be delivered with oxygen, air or oxygen–nitrous oxide mixtures, so nitrous oxide is not obligatory.
Reference: Andrews JJ, Johnston RV. The new Tec 6 desflurane vaporizer. Anesthesia & Analgesia. 1993;76(6):1338–1341. https://pubmed.ncbi.nlm.nih.gov/8498675/