Sweat artifacts
,technical or other disturbances which are not due to brain activity.
The Massive amplification magnifies all manner of disturbances such as
EKG and Pulse artifacts, electrode
and movement, and IV and 60 Hz artifacts and
Sweat artifacts
,
which represent salt solution between electrodes shorting them out.
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Both artifacts are illustrated and are recognized by their periodicity.
The EKG shows periodic QRS complexes
as the EKG is a much larger electrical signal than EEG.
Pulse artifact is caused by a pulse under an electrode moving that electrode
periodically. Both are easily recognized usually but can be a problem.
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ELECTRODE AND
OTHER MOVEMENT ARTIFACTS
Patient movement artifacts are abrupt with a rapid upstroke in almost all instances.
They are large in amplitude and last a long time by EEG standards.
A 'POP' is a brief electrode shift which can be mistaken for a spike by the
naive but it is seen usually in only two adjascent channels and not three as.
occurs with epileptic spikes.
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INTRAVENOUS ARTIFACT and 60 Hz
ARTIFACTS
These artefacts are seen commonly in ICU recordings and both are electrical
interference. The 'drip' artifact is shown in red; it is periodic and small in
amplitude and easily recognized. Sixty Hz is seen where the electrode
contacts are poor, grounding is inadequate and electrical contrivances
are in use close by. This causes spikes at 60 per second - an inkblot at
at usual paper speeds.
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