Nitrous oxide anaesthesia induced at atmospheric and hyperbaric pressures: Part ii: Comparison of measured and theoretical pharmacokinetic data

Abstract

A mathematical model in the form of an Algol program for a digital computer is used to match, breath by breath, experimental studies (as described in Part I) of nitrousoxide anaesthesia in two volunteers. Initially, normal values are assumed for attributes, such as cardiac output, which were not measured. This yields computed results which show some systematic deviations from the experimental results. A modified model, incorporating some elaborations, and using some non-normal values suggested by the experimental data, gives computed results which are consistent with the measured data, in both hyperbaric and hypoxic experiments, provided that some change of FRC, different for the two subjects but fairly consistent for each, is accepted. Computed values of the uptake of nitrous oxide increased with inspired partial pressure, inspired concentration, cardiac output and ventilation. Computed values of brain tension are used to speculate on the perfusion of the region or regions of the brain which, in the circumstances of these experiments, were associated with loss of consciousness. © 1974 Oxford University Press.