Fig. 2. ( A ) The data used for the initial estimates of the linear function linking the brain concentration (Cbrn) to the Bispectral Index (BIS). The data were fitted to the function BIS = BISslp× Cbrn+ BISint. The Model Selection Criterion was 3.62, and the parameter values were BISslp=−4.46 SD 0.16 units · mg−1· l and BISint= 77.7 SD 1.94 units. These were used as starting values for this component of the combined kinetic–dynamic model for the brain. ( B ) The data used for the initial estimates of the Emaxfunction linking the brain concentration (Cbrn) to the percent reduction in cerebral blood flow from baseline (Qbrn,%). The data were fitted to the function Qbrn,%= Qbrn,baseline− (Emax,CBF× Cbrn)/(EC50,CBF+ Cbrn). The Model Selection Criterion was 3.95, and the parameter values were Baseline = 101.5 SD 1.8%, Emax= 79.5 SD 3.5%, and EC50= 6.17 SD 1.02 mg/l. These were used as starting values for this component of the combined kinetic–dynamic model for the brain.