An evaluation of gas density dependence of anaesthetic vaporizers.

Four commonly used vaporizers were studied for the effect of carrier gas density on vaporizer output. Vapour concentrations from a halothane Cyprane (Fluotec) Mark 2 increased in relation to the density of carrier gas, whereas the concentrations delivered by an enflurane Ohio vaporizer decreased. The halothane Cyprane (Fluotec) Mark 3 and enflurane Cyprane vaporizers were largely independent of density. Of clinical importance, nitrous oxide/oxygen (75/25), compared with oxygen alone, increased the vapour concentration outputs of the halothane Mark 2 up to 30% and decreased the outputs of the enflurane Ohio unit up to 20%.