Fig. 4. Parameter time series during induction of anesthesia in a randomly selected patient (propofol) from study A. Parameters approximate entropy (with  n =2;  dotted line ) and permutation entropy (with  n =5;  solid line ) including a frequency range from 0.5 Hz to 30 Hz (  A ), and approximate entropy (with  f ^high= 70 Hz,  n =7;  dotted line ) and permutation entropy (with  f ^high= 42 Hz,  n =9;  solid line ) including the electroencephalographic gamma band (  B ). Parameter values are normalized to the interval (0,1). The  dashed lines indicate changes of the level of consciousness: loss of consciousness at induction (LOC1: 215 s) and return of consciousness after intubation (ROC1: 785 s), followed by second loss of consciousness (LOC2: 845 s). Permutation entropy indicates the state of consciousness better than approximate entropy. The inclusion of high-frequency components may lead to more stability during wakefulness. Parameter calculation was performed in time steps of 5 s using a signal 10 s in duration (overlapping factor 2).