Fig. 2. Comparison of the sigmoid concentration–response curves for suppression of H-reflex amplitude (dashed line ) and Bispectral Index (dotted line ) calculated from normalized data of all patients (generated from individual concentration–response curves), and the logistic regression curve for the suppression of the motor response to noxious electrical stimulation (continuous line ). Horizontal error bars = standard errors of the EC50values generated by the computer fits; circles = individual movement responses (filled = positive response; open = no response). H-reflex amplitude has an EC50of 1.5 vol% and a slope parameter of 4.3. Logistic regression of the motor responses yielded an EC50of 1.6 vol% and a steepness coefficient of 8.1 (see Results). c(sevo)et= end-tidal sevoflurane concentration.