Modern anaesthesia machines use an interlock mechanism such as the Selectatec series on the vaporizer back bar. What is the primary purpose of this system?

• A To prevent back pressure transmission into the vaporizer during positive pressure ventilation
• B To shut off gas flow if the oxygen supply fails
• C To compensate for changes in vaporizer temperature
• D To ensure that only one vaporizer can be turned on at a time, preventing concurrent delivery of two agents ✓

Explanation

The interlock system mechanically links all vaporizers mounted on the back bar. Turning one dial on locks the dials of every other vaporizer, so two volatile agents cannot be delivered simultaneously. Temperature compensation is achieved by a bimetallic strip inside each vaporizer, fail-safe devices act on the gas supply lines, and pumping effect mitigation uses baffles and check valves, none of which is the interlock function.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.