How BIS monitoring works
Monitoring Bispectral Index (BIS™)
5-4 Efficia CM Series Rack and Modules Instructions for Use
• Spectral Edge Frequency (SEF)
The Spectral Edge Frequency (SEF) is the frequency at which 95% of the total
power lies below it and 5% lies above it.
• Total Power (TP)
A measure of the absolute total power in the frequency range from 0.5 to 30.0 Hz.
The value is in dB with respect to 0.0001 V
2
• Burst Count (BC)
When a BIS Extended Sensor is in use, the Burst Count (BC) is displayed above the
EEG waveform display. The BC is an alternative method of quantifying suppression,
reported as the number of EEG bursts per minute. The system defines a “burst” as a
short period of EEG activity, preceded and followed by periods of inactivity. When
the signal quality is low or when the Suppression Ratio is less than 5, the Burst
Count is not displayed.
• Patient Interface Cable (PIC)
This cable is the connection between the electrodes and the BISx or BISx4 module.
How BIS monitoring works
A sensor placed on the patient’s forehead transmits EEG signals to the BIS module. The
BIS module filters the data, analyzes it for artifact and processes it using digital signal
techniques, then sends the data to the monitor for display. The purpose of processing the
EEG waveform data is to extract characteristic features from the complex signal in order
to provide easier pattern recognition of changes over time during the recording.
Figure 5-2 BIS Range Guidelines
BIS measurements are displayed in both a waveform pane and a numeric pane. When
using a Quatro, Extended or Pediatric sensor, EEG (BIS)/EEG2 (BIS) waveforms and BIS/
SQI
1
/SEF/EMG
2
/SR/TP parameters are available.
When using an Extended Sensor, the BC parameter is also available.
BIS Range and Clinical State
BIS
Index
Range
100 Awake
Responds to the voice normally.
80 Light/Moderate Sedation
May respond to loud commands
or mild prodding/shaking.
60 General anesthesia
Low probability of explicit recall.
Unresponsive to verbal stimulus.
40 Deep hypnotic state
20 Burst suppression
0 Flat Line EEG
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