Environmental artifacts in EEG recordings can stem from various sources and devices present in the patient's surroundings.
1. 50/60 Hz Ambient
Electrical Noise:
oDescription: This type of
artifact is often caused by the alternating current (AC) present in the
electrical power supply.
oCharacteristics: It typically
manifests as medium to low amplitude noise with a monomorphic frequency
corresponding to the AC frequency (e.g., 60 Hz in North America).
oDistribution: The artifact
may be present across all EEG channels or in isolated channels with poorly
matched impedances.
2. Intravenous Drips:
oDescription: Electrical
artifacts can be produced by intravenous or other drip infusions, particularly
those with electrostatically charged droplets falling near the recording
electrodes.
oCharacteristics: These artifacts
may appear as spike-like EEG potentials and are associated with the movement of
electrically charged droplets.
o Identification: Regularity and
occurrence with the drips are key factors in identifying this type of artifact.
3. Electrical Noise
from Devices:
oDescription: Various
electrical devices can produce high-amplitude irregular activity resembling
spikes, polyspikes, or muscle potentials due to switching electromagnetic
fields within the devices.
oCharacteristics: The artifact
occurs with the device's activity and may exhibit a fixed recurrence pattern
according to the device's settings.
4. Mechanical Noise
from Devices:
oDescription: Mechanical
devices such as ventilators and circulatory pumps can generate artifacts with
slower components than electrical motors.
oCharacteristics: Mechanical
artifacts often exhibit rhythmicity related to the vibrations produced by the
device and may repeat with a fixed interval, showing slow waves or a complex
mixture of frequencies.
5. Modern Infusion
Pumps:
oDescription: Modern infusion
pumps can produce intermittent electrical artifacts related to the pump motor,
while drip infusions without a motor can also generate electrical artifacts.
oCharacteristics: The artifact is
due to the moving electrical field of electrostatically charged droplets
falling with the drip infusion, appearing as spike-like EEG potentials.
Understanding the
different types of environmental artifacts and their characteristics is
essential for recognizing and distinguishing them from physiological or
pathological patterns in EEG recordings. Proper identification and
differentiation of environmental artifacts contribute to the accurate
interpretation of EEG data and help ensure the quality and reliability of EEG
analysis in clinical practice and research.
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