Which volatile inhalation anaesthetic agent must be used in a temperature controlled vapouriser?

• A. Sevoflurane
• B. Desflurane
• C. Isoflurane
• D. Halothane

Answer: (B)

Desflurane is unique because its boiling point is very close to room temperature, so its vapor pressure changes a lot with even small temperature shifts. To deliver a precise, known concentration to the patient, the liquid must be heated and kept at a constant temperature in a dedicated thermostatically controlled vapouriser. This ensures the amount of desflurane vapor delivered remains stable regardless of ambient conditions.

Other volatile agents have higher boiling points and produce vapour more predictably at typical room temperatures, so their vapourisers don’t require the same heating to maintain accuracy. They can be used with standard variable-bypass, temperature-compensated designs without a heated chamber.