Large volume N2O uptake alone does not explain the second gas effect of N2O on sevoflurane during constant inspired ventilationâ€

We confirmed the existence of a SGE of N2O. Surprisingly, when using an Fa of 65% N2O, the magnitude of the SGE was the same with large or small VN2O. The classical model and the graphical representation of the SGE alone should not be used to explain the magnitude of the SGE. We speculate that changes in ventilation/perfusion inhomogeneity in the lungs during general anaesthesia result in a SGE at levels of VN2O previously considered by most to be too small to exert a SGE.