Artifact Recognition & Troubleshooting

Artifacts

Artifacts Definition : A Weed Can affect any channel Range from annoyance to

nightmare

An Ounce of Prevention… Electrode Impedances

Low & Equal Common mode rejection

G1> Signal + BN + ENG2 > - BN + EN = Signal

Artifacts aren’t always easy to see at 4:00 am and the screen looks like

this

Non-Physiologic Artifact

60 HzPoor electrode connectionImportance of low

impedanceUse of notch and High

Frequency filters

60 Hz Artifact

Going………………..Going………………..GONENo filters applied

60 Hz Artifact

HFF at 35 Hz

60 Hz Artifact

HFF set at 15 Hz

Popping Baseline sway

Recording from too large an area

Non-Physiologic Artifact

HFR or sleep with a beat

Dissimilar metals Different

impedance properties

Non-Physiologic Artifact

Sampling Rate

Aliasing Sampling rate too low

Power surges Surge protection

Loose connections Headbox, amplifier, computer

Non-Physiologic Artifact

Non-Physiologic Artifact Amplifier blocking

A type of overload, may be due to popping Amplifier sensitivity may be too high if waveforms

are clipped Typically low so all amplitude waveforms get

recorded This keeps high amplitude waves from clipping

Low Sens Too High

150uV

Non-Physiologic Artifact Sampling skew - when all channels are not

sampled simultaneously

First Chan.

Last Chan

Erroneous output when data is Reformatted

Simultaneous Data Sample

Non- Simultaneous

Data Sample

Physiologic ArtifactsSometimes its in the eye of the beholder

Physiologic Artifacts

Muscle Reposition leads Let patient fall asleep

Movement

Movement & Muscle Artifact

Physiologic Artifacts Other Movement artifacts

Eye movement Bruxism

Can resemble spike & wave complexes or synchronous delta

Head Tremor Tongue movement

Physiologic Artifacts EKG Artifact

Place reference leads high

Move references to earlobes

Join A1 & A2 Pulse Artifact

Reposition leads Pacemaker

ECG Artifact

*Atlas of Sleep Medicine – Nic Butkov

Physiologic Artifacts

Respiration Raise LFF or Lower TC Reposition

wires

Respiratory Artifact

Physiologic Artifacts Sweat

Cool patient off

Remove blankets

Lower room temp

Add fan etc. Raise LFF or

decrease TC

Sweat Artifact

Importance of Re-referencing to Troubleshoot Verify Impedance during the

recording to zero in on bad lead

Find the problem electrodeDid it come off, come out,

break? Re-reference if possible or use

back-up leads

Troubleshooting A1+A2

*Atlas of Sleep Medicine – Nic Butkov

Anticipate Exam

QuestionsIt will help in case you don’t have a bigger brain to pull

out during the exam

Exam Content Areas Related to Artifacts

Domain 2, Task 4 Observe cal tracings to verify

signals are artifact free and make adjustments

Consider questions related to: Correct software settings Amplifier function

Exam Content Areas Related to Artifacts

Domain 2, Task 5 Perform appropriate physiologic

calibrations to ensure proper signals Consider questions related to:

Appearance of any artifacts Troubleshooting prior to lights out

• As opposed to after lights out• Check leads, hookup, etc.

Poor impedance leads to what artifacts

Exam Content Areas Related to Artifacts

Domain 3, Task 3 Monitor study tracing quality to ensure signals

are artifact free and make adjustments Consider questions related to:

Troubleshooting after lights out• Determining bad lead• Re-referencing• Use/abuse of software filters

Change in environment Effect of reference or ground coming off Sensor displacement When to intervene

Exam Content Areas Related to Artifacts

Domain 3, Task 5 Document routine observations, changes

in procedure, and significant events in order to facilitate scoring and interpretation

Consider questions related to: What is important to document Documentation of:

• Electrode & sensor replacement

• Changes to the environment Accuracy & timeliness of documentation

Exam Content Areas Related to Artifacts

Domain 4, Task 1 Score sleep/wake stages by

applying professionally accepted guidelines

Consider questions related to: What artifacts impair scoring What to do if staging is

compromised Use/abuse of software filters

Exam Content Areas Related to Artifacts

Domain 4, Task 2 Score clinical events according to

current professionally accepted guidelines

Consider questions related to: What artifacts impair scoring What to do if event scoring is

compromised Use/abuse of software filters