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6.4 Electrode check
To ensure the proper working of the system, the impedance values may not exceed a
certain threshold. Furthermore, make sure that the impedance values of the individual
electrodes are as uniform as possible. At too high impedances or impedance
differences no evaluation of the incoming EEG data is possible, and an appropriate
message (NARCOTR CHECK IMP) is outputted.
Impedances Differences of impedances
Threshold values
< 8 kΩ < 5 kΩ
6.5 Error messages
The following error messages are outputted:
NARCOTR LEAD OFF Patient lead is not connected.
NARCOTR CHECK IMP One or more impedance values have exceeded the
maximum limit. Check the position of the electrodes on the
patient's head and the connections at the electrode lead.
NARCOTR 50/60 HZ AC artifacts occur in the signal.
NARCOTR INTERFER Errors may occur in the EEG signal, e.g. by high-frequency
surgery (cautery).
EMG No classification due to high intensity of the electrical
muscle activity.
• In case of excessive load of artifacts the Narcotrend-Index is not
calculated.
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