Fig. 6. End-tidal override controller: Despite a bispectral index value less than the set point, the controller kept a minimal end-tidal concentration of 0.4 vol.% constant. At 15:02 the minimally allowed end-tidal target concentration was decreased to 0.3 vol.% by the anesthesiologist, which was followed by the controller. A slightly higher bispectral index value can subsequently be observed.