Fig. 2.  Principles of electroencephalography training for anesthesiologists. The readings shown represent examples of possible readings that may be seen in conjunction with each frontal electroencephalography trace. The electroencephalography traces show 3-s epochs (x-axis) and the scale (y-axis) is 50 μV. Electroencephalography (EEG) waves in decreasing frequency are as follows: γ, >30 Hz; β, 12–30 Hz; α, 8–12 Hz; θ, 4–8 Hz; δ, 0–4 Hz. The section outlined in the first trace is a blink artifact and the section outlined in the third trace is a sleep spindle. Amp = amplitude; BIS = bispectral index; BS = burst suppression; BSR = burst-suppression ratio; ETAC = end-tidal anesthetic concentration; f = frequency; MAC = minimum alveolar concentration; SEF⁹⁵= spectral edge frequency (below which 95% of the EEG frequencies reside).