SECTION 3 OPERATING THE A-2000
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3-6
3.3.2 The Signal Quality Region
The Signal Quality Region is located in the upper right section of the screen. When the
[MENU/EXIT] key has been pressed, this area is used to display the Setup Menu. In the
BIS Log display, it displays instructions. In all other modes, the following signal quality
information is displayed. (Refer to Figure 11.)
3.3.2.1 The Signal Quality Index (SQI) Bar Graph
The SQI is an indication of the quality of the EEG signal that is received and processed
into screen data. The SQI graph represents a scale of 0 - 100, marked off at intervals of
10. Optimal signal quality for the EEG channel source is indicated when the bar extends
to the right side (+) of the graph.
3.3.2.2 The Electromyograph (EMG) Bar Graph
The EMG graph shows the power (in decibels) in the frequency range 70 - 110 Hz. This
frequency range contains power from muscle activity (i.e., electromyography or “EMG”)
as well as power from other high-frequency artifacts. A low level of EMG is indicated
when the bar is not present or at the left side of the graph.
3.3.2.3 The Electroencephalogram (EEG) Waveform Display
Filtered EEG waveforms are displayed with a sweep rate of 25 millimeters per second
and a scale of 25 microvolts per division (default). EEG filters can be turned off and the
sweep speed and amplitude can be changed in the Display Parameter Setup screen.
3.3.2.4 The Suppression Ratio (SR) Number
Suppression ratio is a calculated parameter to give the user an indication when an
isoelectric (flatline) condition may exist. Suppression ratio is the percentage of time over
the last 63-second period that the signal is considered to be in the suppressed state.
For example: SR=11 (isoelectric over 11% of the last 63 second review). The SR is
displayed in the upper right corner of the screen.
3.3.2.5 The Burst Count (BURSTS/MIN)
When a BIS Extend sensor is in use, the Burst Count is displayed just below the SR
number. Burst Count is an alternative method of quantifying suppression, reported as
the number of EEG bursts per minute. When the signal quality is low (SQI less than 15)
or when the suppression ratio is less than 5, the burst count is not displayed.
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