Which volatile anaesthetic agent has the highest vapour pressure at 20°C, necessitating a heated, pressurised vaporiser (Tec 6) for its delivery?

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

Explanation

Desflurane has a vapour pressure of approximately 669 mmHg at 20°C, which is very close to atmospheric pressure (760 mmHg), making it nearly boil at room temperature. A conventional variable-bypass vaporiser cannot accurately deliver desflurane, so the dedicated Tec 6 vaporiser heats the agent to 39°C (vapour pressure ~1550 mmHg) and injects precise amounts under pressure. Isoflurane, sevoflurane, and halothane have much lower vapour pressures and can use standard vaporisers.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.