18 Monitoring BIS
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BIS Continuous Impedance Check
This checks:
• the combined impedance of the signal electrodes plus the reference electrode.
This is done continuously and does not affect the EEG wave. As long as the impedances are
within the valid range, there is no notification of this check or its results.
• the impedance of the ground electrode.
This is done every ten minutes and takes approximately 4 seconds. It causes an artifact in the EEG
wave, and the message
Ground Check is shown on the monitor screen during the check. If the
ground electrode does not pass this check, another check is started. This continues until the
ground electrode passes the check.
If the Continuous Impedance Check interferes with other measurements, it can be switched off. To do
this:
1 In the Setup BIS menu, select Cont. Imp. Check.
2 Select On or Off as required.
CAUTION
Switching the continuous impedance check off will disable automatic notification to the user of
impedance value changes, which may lead to incorrect BIS values. Therefore, this should only be done
if the check interferes with or disturbs other measurements.
When a Semi-reusable Sensor is in use the continuous impedance check cannot be switched off. If it is
switched off when the sensor is connected, it will automatically be switched on again.
BIS Cyclic Impedance Check
This measures the exact impedance of each individual electrode. It causes a disturbed EEG wave, and
the INOP
BIS IMPEDANCE CHCK is shown on the monitor screen during the check.
Starting a Cyclic Impedance Check
The Cyclic Impedance Check is automatically started when a sensor is connected. To manually start a
Cyclic Impedance Check:
•select
Cyclic Check in the Setup BIS menu to toggle between On and Off, or
•select
StartCyclicCheck in the BIS window.
Stopping a Cyclic Impedance Check
The Cyclic Impedance Check stops automatically if the impedances of all electrodes are within the
valid range. To manually stop a Cyclic Impedance Check:
•select
Cyclic Check in the Setup BIS menu to toggle between On and Off, or
•select
Stop CyclicCheck in the window.
If you stop a Cyclic Impedance Check before the ground electrode has passed, a ground electrode
impedance check will be started automatically. This cannot be switched off.
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