EditorIt is a common misconception that turning off the vaporizer while leaving the fresh gas flow (FGF) on, during endotracheal intubation, prevents pollution of the anaesthetic room by inhalational agents.
After switching off the vaporizer but leaving the FGF running, it would take four times the time constant to eliminate all the volatile agent from the circuit. Therefore, with the vaporizer turned off, and despite the usually brief time taken to intubate, anaesthetic gases still leak into the atmosphere all the time during intubation if the FGF is left on.
We suggest that the vaporizer setting be left where it is but the FGF be turned off during intubation. This practice would completely eliminate the discharge of the anaesthetic gas mixture into the environment. It would also be beneficial for a variety of other reasons. It would prevent a fall in concentration of volatile agent in the gas mixture within the circuit, thus reducing the likelihood of awareness post-intubation, and one is more likely to notice a non-filling reservoir bag than a vaporizer that is turned off.1 It may also be more cost-effective, by reducing the amount of gas and volatile agent consumed.
1 Harlow, UK
2 Capetown, South Africa
References
1 Rassam S, Baraz R, Stacey M. Gas off or vaporiser off. Anaesthesia 2004; 59: 6289[Medline]
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