Which volatile anaesthetic would be incompatible with a standard non-temperature-controlled vapouriser?

• A. Sevoflurane
• B. Desflurane
• C. Isoflurane
• D. Nitrous oxide

Answer: (B)

Desflurane has a very low boiling point and a high vapor pressure, so the amount that actually leaves the vaporiser is extremely sensitive to ambient temperature. Non-temperature-controlled vapourisers assume stable conditions and can't reliably deliver a consistent concentration of desflurane. To maintain accurate dosing, desflurane must be delivered through a heated, temperature-controlled vapouriser that keeps the output stable regardless of room temperature.

The other agents can be effectively vaporised by standard vapourisers at ambient temperature, and nitrous oxide is delivered as a gas rather than through a liquid vapouriser, so it doesn’t require heating.