3.12 Depth of Anesthesia and Sedation Module
177
Before analyzing the EEG, its primary processing is carried out, the purpose of which is to re-
move motor artifacts, bursts on the EEG caused by the action of various kinds of external elec-
trical interference. In the course of this processing, the detected interfering components are re-
moved from the EEG signal and the original form of the EEG signal is restored.
If the interference cannot be removed without distorting the shape of the initial EEG, then this
EEG fragment is discarded and does not participate in further analysis.
The signal quality index SQI considers the values of EEG cable electrodes impedance, the
presence of artifacts, high-frequency interference, network noise in the EEG and decreases lin-
early from 100% to 0%:
with increasing of total duration of rejected EEG signal fragments from 0 to 30 s;
with increasing of level of power mains disturbances in the EEG from 100 to 5100
μV;
with increasing of level of high-frequency interference from 40 to 80 dB;
with increasing of electrodes impedance from 10 to 60 kOhm.
At zero SQI coefficient, display of values of the brain activity index AI, the SR coefficient and the
EMG component level are blocked. At the same time, the message about the most significant
reason of SQI decrease is displayed.
Measurement of the interference level in EEG signal is performed continuously. The measure-
ment of electrodes impedance is performed automatically every 6 minutes, or can be started
manually by the user (p. 3.12.4). In addition, the measurement of electrodes impedance is au-
tomatically triggered when there are sharp changes in the noise background in the EEG signal
in order to detect changes in the impedance or reset of the electrode.
An increase in the impedance of electrodes can lead to an increase in the
level of noise in the EEG. The control of values of these parameters is car-
ried out in a separate window of EEG signal quality indicators (p. 3.12.4).
To track the dynamics of the patient's state change, the values of the brain activity index AI and
the level of the EMG component are displayed in the graphical trend window. Range of AI
presentation in graphic form is from 0 to 100 rel. units The EMG level measured in the range
from 0 to 100 dB is graphically displayed in the most significant clinical range from 30 dB (back-
ground level under anesthesia) to 70 dB (typical level when awake).
3.12.2. Preparing for the Monitoring of the Depth of Anesthesia
The skin has poor electrical conductivity, so skin preparation is very important to ensure good
contact of the electrodes with it. Before applying electrodes, prepare the patient's skin:
If nesessary, shave off the hair in places where electrodes are applied;
to improve electrical contact, you can carefully remove the upper layer of the epi-
dermis (stick and remove the adhesive plaster several times);
thoroughly wipe the skin with a sponge with ethyl alcohol and dry with a gauze or
cotton sponge.
Attach the disposable electrodes to the clips on the ends of the EEG cable.
Peel off the protective film from its adhesive surface. When using old electrodes with a long
shelf life or when its gel layer dries up, if you cannot achieve an impedance value of less than
25 k
Ω, apply contact paste or several drops of physiological 0.9% sodium solution to the central
part of the electrode chloride.
Application of electrodes with
sufficient
reserve of storage period and their
careful placing on a patient is essential condition to get high-quality signal.
Place electrodes on prepared area of patient's skin and press them carefully to make electrodes
closely fitting and to ensure secure fixation of the electrode. It is recommended to evaluate ac-
tivity index AI after few minutes of electrodes application, after their impedance reduces below
25 kΩ
Summary of Contents for MPR6-03
Page 1: ...Patient Monitor MPR6 03 User Manual RM 501 01 000 01 01 UM Version 7 05 2020 ...
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