SECTION 5 FEATURES AND CAPABILITIES
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5-2
5.2.3 Electromyograph (EMG) Indicator
EMG 70-110 Hz Bar Graph Display Range 30 – 55dB
The power (in decibels) in the frequency range 70-110 Hz is labeled “EMG.” This
frequency range contains power from muscle activity (i.e., electromyography or “EMG”)
as well as power from other high-frequency artifacts. The EMG bar graph displays this
activity. It is optimal when the bar is empty.
5.2.4 Electroencephalogram (EEG) Waveform Display
Sweep speed – 25 mm/sec Amplitude – 25 μV/ division
Filtered EEG waveforms are displayed with a sweep rate of 25 millimeters per second
and a scale of 25 microvolts per division. Filters may be turned off in the Display
Parameters screen. The sweep speed can be changed to 15, 25 or 30 mm/sec and the
amplitude to 5, 10, 25, 50, 100 μV/ division.
5.2.5 Filters
ON (2 – 70 Hz with notch) or OFF (.25 – 100 Hz)
The A-2000 uses filters to screen out undesirable interference from the raw EEG signal
display. If you prefer to observe the raw EEG without the filters, they may be turned off.
The Notch filter includes filters for both 50 and 60 Hz. Filters ON or OFF does not affect
processing of the Trend variables (i.e., BIS, EMG, SR, and SQI), but will affect the DSA
display. Viewing the EEG signal without filters may aid in troubleshooting signal
problems.
5.2.6 Suppression Ratio (SR)
Range = 0 – 100%
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. When SR reaches 100%, the message
“Isoelectric EEG Detected” will notify the user. Suppression ratio can be plotted over
time as a secondary trend in the Graphic Display Region.
5.2.7 Burst Count (BURSTS/MIN)
Range = 0-20
Burst Count is an alternative method of quantifying suppression, available only when a
BIS Extend sensor is in use. The system defines a “burst” as a short period of EEG
activity, preceded and followed by periods of inactivity. Computed from suppression
data, it is reported as the number of EEG bursts per minute. The burst count is
displayed in the upper right corner of the screen, under the suppression ratio, and may
also be graphed as a secondary variable in the Graphic Display Region. 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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