GASEOUS HOMEOSTASIS AND THE CIRCLE SYSTEM - VALIDATION OF A MODEL

The performance of a model of a subject breathing from a circle system has been examined in relation to nitrogen and helium. The ability of the model to maintain a nitrogen steady-state after perturbation of an existing nitrogen equilibrium, the washout of nitrogen from the subject model on breathing oxygen, and the estimation of functional residual capacity using a rebreathing method with helium as an indicator have been assessed. The predictable and accurate performance of the model in these studies, together with its ability to reproduce the results of a number of previously published studies in man, suggest that the model can be used to predict the behaviour of circle systems when used with inhaled anaesthetic agents.