Effect of nitrous oxide on the output of three halothane vaporizers

The effect of changing the composition of the carrier gas from 66% nitrous oxide in oxygen to 100% oxygen was examined in three halothane vaporizers (Fluotec Mk 3, Drager Vapor 19 and Abingdon halothane vaporizer). All showed a transient increase in output following the discontinuation of the nitrous oxide. The effect was minor (2-8% of indicated output) and short-lived (1-4 min) at the fresh gas flows used. The steady-state output of the vaporizers, once the transient response was over, was found to be lower with 100% oxygen as carrier gas than it had been with 66% nitrous oxide in oxygen. The difference was minor in the case of the Drager Vapor 19 (1% of indicated output) and Fluotec Mk 3 (5% of indicated output), but greater in the case of the Abingdon (15% of indicated output).