Fig. 1

Normalization of electroencephalography after L2 electrode repositioning. a A snapshot of the Root® with SedLine® Brain Function Monitoring (Masimo Inc, Irvine, CA) is presented. A rhythmic, heart rate time-locked pulsation artifact is overlying L2. b Following L2 electrode repositioning, a pulsation artifact has completely disappeared. All four electroencephalogram (EEG) traces show a burst-suppression pattern. c Two 10-s samples (left and right) of four EEG channels (L1, R1, L2, and R2), electrocardiogram (ECG), and plethysmography (pleth) show how the waveform of L2 changes after electrode replacement. The synchronization between ECG/pleth versus EEG is not perfect due to separate standalone monitoring devices, but it can be seen that the pace of the low fluctuation in L2 EEG is similar to that of the heart rate and pleth. The units of EEG and ECG signals are microvolts. d Heart rate (red) and instantaneous frequency of the low-frequency component of L2. Both sample-by-sample estimate and smoothed version over a 4-s window are shown in black color. The time axis values correspond to those in c above. The Roman numerals I and II indicate the timepoints of making the start of the electrode replacement (I) and recovery of the EEG signal (II), respectively