Background: Recently, an increasing number of electroencephalogram (EEG)-based monitors of the hypnotic component of anesthesia has become available. Most of these monitors calculate a numerical index reflecting the hypnotic component of anesthesia. Most of the underlying algorithms are proprietary. Therefore, a quality check or comparison of different indices is very complex.
Methods: Because there is limited information about the algorithms used for index calculation of the different monitors, a reliable comparison or test of the monitors is possible only if the same set of EEG data are presented to each monitor.
Results: Parallel EEG monitoring during surgery is limited to two or three monitors because the space for electrode placement on the head is limited. This problem can be solved by using the EEG player to play back recorded EEG data to different monitors.
Conclusions: The output of the player corresponds to the original EEG signal. A comparison of different indices based on identical EEGs is therefore possible. The index reproducibility can also be checked, if the same signal is presented to different monitors.