Figure 2. Schematic diagram of our 14-compartment physiologic model. (Inset) The various versions with special emphasis on nonpulmonary elimination (NPE). The fraction NPE on the ordinate is the fraction of the amount of anesthetic agent irreversibly lost from the hepatic blood flow. The arterial halothane concentration is on the abscissa. Version A has the identical structure of A in the previous validation study for isoflurane and assumes that NPE is zero. Version C has been used only in the enflurane validation study and uses a constant fraction of NPE. Version D incorporates a nonlinear NPE following Michaelis-Menten kinetics. Versions A, C, and D use fixed partition coefficients, whereas A' and D' adopt age-related partition coefficients. (c)v = (central) venous; a = arterial.