Artifacts and Troubleshooting

Question 1

____ refers to an extraneous
signal appearing in a recording
channel on the PSG.

Answer 1

Artifact

Question 2

____ are electrical signals
recorded in a channel that cause
the desired signal to become
harder to read.

Answer 2

Artifacts

Question 3

After electrodes are placed on the patient, an _____
should be performed to assess the quality of the signals.

Answer 3

impedance check

Question 4

______ refers to
resistance to a current.

Answer 4

Electrical impedance

Question 5

When electrical flow is impeded or resisted, a signal is more likely to be contaminated with ___ or extraneous electrical activity.

Answer 5

artifact

Question 6

Impedance values should be __
and fairly ___ in measurement.

Answer 6

low / equal

Question 7

The AASM recommends that
impedance values below _____ be achieved.

Answer 7

5 kiloohm

Question 8

Low and equal impedance values
are associated with _____ that are less likely to contain artifacts.

Answer 8

higher-quality recordings

Question 9

______ are associated with an increased chance of contamination with
artifacts and occur when an
electrode is not securely placed
against the skin or scalp, when the electrode site has not been
properly cleaned, or when the
sensor is faulty, broken, or dirty.

Answer 9

High impedance values

Question 10

Artifacts can originate from the
____, the ____, or ____, and _____
vary.

Answer 10

patient, equipment, external
sources, corrective methods

Question 11

_____ is a fast-wave
activity that depicts the
electrical activity of the
patient’s heart and appears in a
channel other than the ECG
channel.

Answer 11

ECG artifact

Question 12

This is a common artifact in
patients with hypertension. The
increased blood pressure in
hypertensive patients causes
the ____ to be felt easily in
areas of the body away from
the heart.

Answer 12

pulse / ECG Artifact

Question 13

_____ is most commonly
seen in the EEG,
electrooculogram (EOG), chin
EMG, and leg EMG channels
and presents itself as a single
fast wave appearing
approximately every ___,
depending on the underlying
heart rate.

Answer 13

ECG artifact / second

Question 14

The ____ can be easily
identified by lining up the
extraneous signal with the
patient’s QRS complex in the
ECG channel.

Answer 14

artifact

Question 15

The primary cause of ECG
artifact is _____

Answer 15

poor electrode
placement.

Question 16

An electrode that is placed
directly over a ____ or an
_____ is likely to detect the
pulse and transmit this signal
to the polysomnograph.

Answer 16

large vein / artery

Question 17

Correction of ECG artifact
relies on identification of the
_____.

Answer 17

source electrode

Question 18

Because the ____ is usually associated with poor electrode placement, the best method of correction is to move any affected electrode to an appropriate ______.

Answer 18

artifact / alternate
location

Question 19

For example, the reference
electrodes M1 and M2 are
usually placed on the ___
process behind the ear. If they
are recording the ECG, these
electrodes can be moved
higher up behind the ear or to
the earlobes.

Answer 19

mastoid

Question 20

If ECG artifact is identified after
the patient falls asleep, it can
be corrected by either _____ or ____

Answer 20

re- referencing or double
referencing.

Question 21

____
is accomplished by changing one of the channel’s inputs
(G2) to an alternate electrode.

Answer 21

Re-referencing

Question 22

_____ is characterized by high-amplitude, high-frequency signals that obscure many or all of the channels and occur as a result of a body movement.

Answer 22

Movement artifact

Question 23

_____ is probably the most
frequently occurring artifact during a sleep study.

Answer 23

Movement

Question 24

Even small muscle
movements can cause ____, ____ changes as the skin moves across the tissues underneath it.

Answer 24

high- amplitude, high-frequency

Question 25

During ____ and _____ procedures, the technologist should instruct the patient to lie still, preferably in the supine position, reducing or eliminating movement artifact.

Answer 25

impedance checks and calibration

Question 26

_____ can be subdivided into several types that include sweat, respiratory, and sway artifact.

Answer 26

Slow-wave artifact

Question 27

Slow-frequency artifacts are characterized by a _____, usually _____ waveforms intruding into one or several channels.

Answer 27

slow frequency / high-amplitude

Question 28

_____ is a type of slow- frequency artifact caused by sweat on the patient’s skin.

Answer 28

Sweat artifact

Question 29

___ from sweat causes a chemical reaction that, in turn, causes slow changes in the frequency of electrical signals.

Answer 29

Salt

Question 30

The ___ and ___ channels are most frequently affected by sweat artifact.

Answer 30

EOG and EEG

Question 31

As the patient sweats from the forehead, often the ground lead is affected, which serves as a reference for all the ___ and ___ channels.

Answer 31

EOG and EEG

Question 32

______ is a slow-frequency artifact that it caused by slow, subtle head movements associated with breathing.

Answer 32

Respiratory artifact

Question 33

____ is commonly caused by swinging movements of the electrode wires or the headbox.

Answer 33

Sway artifact

Question 34

This artifact is usually recognized by ruling out the other two causes or visualizing motion of the head box. (____)

Answer 34

Sway artifact

Question 35

Slow-wave artifacts can be masked by increasing the ______

Answer 35

low-frequency filter (LFF).

Question 36

If the artifact is caused by breathing, as in a respiratory artifact, repositioning the patient’s head on the ___ can be helpful.

Answer 36

pillow

Question 37

if a patient is sweating and slow artifact is noted, it is appropriate to ______ affected by the sweat, dry the area, replace them, and use a fan to keep the patient cool.

Answer 37

remove electrodes

Question 38

Lastly, resecuring the head box can effectively eliminate ____ if that is the source of the artifact.

Answer 38

sway

Question 39

____ is an artifact caused by snoring.

Answer 39

Snore artifact

Question 40

This usually appears in the EEG channels or in the chin EMG.

Answer 40

Snore Artifact

Question 41

____ appear as high- amplitude, high frequency bursts of activity for a short period of time, corresponding with and ending when the snore ends.

Answer 41

Snore artifacts

Question 42

Snore artifact is not correctable by changing filter or gain settings, but it will correct itself when the patient ___.

Answer 42

stops snoring

Question 43

When an electrode is broken or disconnected from the patient or head box, it works as an ___ and detects electrical activity from ____.

Answer 43

antenna / external sources

Question 44

This electrical activity is often referred to as ___ and is usually in the frequency range of ___, because this is the frequency used by most electrical devices and outlets in the United States.

Answer 44

electrical noise , 60 Hz

Question 45

This ____ usually ___ signal appears to dominate any affected channel, obscuring relevant waveforms.

Answer 45

high frequency, / high-amplitude

Question 46

Occasionally ______ may be present when all connections are stable, but an electrical device resides close to the diagnostic equipment.

Answer 46

60-Hz interference

Question 47

Today’s sleep diagnostic systems include a built-in 60-Hz filter, also called a ___ or a ____.

Answer 47

notch filter / line filter

Question 48

This sets a special frequency filter from _____ to help reduce 60-Hz artifact.

Answer 48

59 Hz to 61 Hz

Question 49

____ filters merely attenuate signals outside the filter ranges rather than completely eliminate them.

Answer 49

frequency

Question 50

Therefore, if a ___ signal is present, it will likely affect the quality of the tracing even if the notch filter is applied. As with other artifacts, the optimal method of correction is at the ___.

Answer 50

60- Hz / source

Question 51

The most common cause of 60-Hz artifact is ____ or improper cleaning of the site.

Answer 51

poor electrode application

Question 52

Faulty, broken, or disconnected electrodes can permit the entrance of _____ into the pathway, as can loose cable connections or electrical devices sitting close to the diagnostic equipment.

Answer 52

60-Hz signals

Question 53

_____ and other ____ items touching the electrode also can be potential sources of 60-Hz interference.

Answer 53

Metal jewelry and other metal

Question 54

_____ occurs when high- frequency muscle activity contaminates a channel that is not designed to collect muscle activity.

Answer 54

Muscle artifact

Question 55

___ appears to mimic the activity that is collected in the EMG channels.

Answer 55

artifact

Question 56

On a sleep study, muscle artifact is commonly seen in the __ and ___ channels when a patient is anxious or clenches the jaw or grinds his or her teeth.

Answer 56

EEG and EOG

Question 57

______ is most often observed when the patient is awake and tends to gradually disappear as the patient relaxes and enters sleep.

Answer 57

Muscle artifact

Question 58

______ is characterized by occasional pops or bursts of 60- Hz activity in a channel.

Answer 58

Electrode popping

Question 59

This is usually caused by a loose connection in the signal pathway or a faulty or broken wire.

Answer 59

Electrode Popping

Question 60

_______ often displays itself as just one fast high- amplitude wave, or it may pop for a few seconds at a time before returning to normal.

Answer 60

Electrode popping

Question 61

______ is characterized by a blocking of the pens at the highest and lowest points of the channel parameters.

Answer 61

Pen blocking

Question 62

This artifact occurs when the gain setting in a channel is too high, causing the pen to attempt to reach beyond the upper and lower parameters of the channel.

Answer 62

Pen blocking

Question 63

_____ are two terms used interchangeably to describe the amplitude settings on the polysomnograph.

Answer 63

Gain and sensitivity

Question 64

Although the _____ of the signal remains unchanged and is defined at the source of the signal (the patient), the display of the height of the signal can be adjusted.

Answer 64

actual amplitude

Question 65

When the ____ is increased, the height of the waveform display increases.

Answer 65

gain setting

Question 66

The sensitivity setting is measured in terms of _____

Answer 66

microvolts per vertical millimeter (μV/mm).

Question 67

the ______ is increased, the waveform appears shorter in height.

Answer 67

sensitivity setting

Question 68

Some polysomnographs use a _____, some use a _____, and some have options to use either one or both.

Answer 68

gain setting / sensitivity setting

Question 69

Changing the gain setting from _____ would double the height of the waveform, while changing the sensitivity from ____ μV/mm would half the display of the waveform.

Answer 69

1 to 2 / 20 to 40

Question 70

______ can also negatively affect the signals on a PSG.

Answer 70

Improper filter settings

Question 71

As a general rule, ____ should not be used to correct artifacts because it is likely to eliminate relevant waveforms intended to be recorded from the patient.

Answer 71

filters

Question 72

If the LFF on an EEG channel is increased from the recommended setting of ____, it will attenuate the ____ and _____ will be missed.

Answer 72

0.3 to 3 Hz / slow EEG waves / delta waves

Question 73

If the HFF is decreased from the recommended setting of ____, it will attenuate _____, _____, and other _______.

Answer 73

35 to 10 Hz / alpha waves, spindles, and other fast EEG waveforms.

Question 74

Because of the potential effects of over ____, frequency filters should be used conservatively.

Answer 74

filtering