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71 Cards in this Set

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Alpha rhythm
Sinusoidal EEG activity in the range of 8 - 13 Hz highest in the occipital channel. The wave-form is smooth and regular. The amplitude of the signal decreases when the eyes are open. Must be distinguished from alpha frequency activity, which is 8 - 13 Hz but may be sharp and irregular and my not be most prominent in the occipital channel. Alpha frequency activity may not change with eye opening.
Alternating leg muscle activity (ALMA)
Bursts of leg muscle activity coming first from one leg and then the other. There must be at - least 4 muscle bursts The minimum frequency is Hz. (one burst every other second) and the maximum frequency is 3 Hz (3 bursts per second).
Amplitude
The magnitude of a signal, measured from the top most point (zenith) to the lowest point (nadir). For electrical signals like the EEG, the measurement unit is usually volts or portions of volts. A microvolt (uV) is 1/1,000 volt. In sleep recordings, amplitude is the height of the signal on the vertical (Y) axis.
Apnea
A pause in breathing during sleep. An apnea must last at least 10 seconds in adults and 2 missed breaths in children. Apneas are defined by at least a 90% drop in the amplitude of the thermal sensor signal.
Arousal
An awakening or lightening of sleep. The criteria for scoring an arousal are an abrupt shift in EEG frequency lasting at least 3 seconds, with at least 10 seconds of stable sleep before the event. Sleep spindles do not count in the scoring of arousals. For arousals from R, the chin EMG must increase for at least 1 second in addition to the abrupt shift of EEG frequency.
Asystole
A period with no cardiac electrical activity and no cardiac output or blood flow. For ages 6 and up the period must last 3 seconds or more Atrial fibrillation
Atrial fibrillation
The most common cardiac arrhythmia. Normally, electrical impulses in the heart are generated by the sino-atrial node. In atrial fibrillation, impulses start in the atria and pulmonary veins. Conduction through the ventricles is irregular, leading to an irregular heart rate. Atrial fibrillation is associated with congestive heart failure and increased risk of stroke.
Bradycardia
An abnormally slow heart rate. During waking, a heart rate slower than 60 beats per minute is considered abnormal. The heart rate is usually slower during sleep, and a limit of 40 beats per minute- is used to define bradycardia during a polysomnogram.
Bruxism
Tooth grinding. Bruxism can cause tooth damage and excessive wear. It can occur as chewing movements or clenching of the jaw, or as both. It is common during sleep and during brief arousals from sleep.
Central apnea
A type of apnea with no airflow and no effort to breathe. Central apneas often occur at sleep onset and at high altitude. Patients with Cheyne Stokes breathing often have periods of central apnea. Central apneas last at least 10 seconds in adults and at least 20 seconds in children.
Cheyne Stokes
A pattern of breathing in which the volume and rate of breathing increases (crescendo) and breathing decreases (decrescendo) with a cycle length of about 60 seconds. It is most often associated with heart failure, but can occur with any problem causing damage to the respiratory centers such as stroke or brain tumor.
Distribution
When used in polysomnography, distribution means the location on the scalp that is the origin of an EEG signal. In recordings using a single reference electrode (such as the standard polysomnogram montage) this is determined by the amplitude of the signal. For example, the highest amplitude of slow wave activity is M the frontal channel. This is taken to mean that the signal comes from the frontal lobes.
Dominant posterior rhythm (DPR)
The EEG activity in children that is the same as alpha rhythm in adults. Like alpha rhythm, the activity usually goes away with eye opening. It is seen in infants 3 to 4 months post term at 3.5 to 4.5 Hz, at 5 to 6 Hz by 5 to 6 months and at 7.5 to 9.5 Hz at 3 years of age. It should be in the alpha frequency range in all children by 12 years of age.
Duration
The duration of a signal is the time it takes for a full cycle ,of a waveform to occur. The duration of a signal is the inverse of the frequency (1/frequency). The duration of a 3 Hz signal is
I/3 or 0.33 seconds. The AASM Manual uses duration criteria for some signals (for example,
K complexes last more than 0.5 seconds) and frequency criteria for others (eye blinks occur
at a rate of 0.5 to 2 Hz).
Ectopic beats
A heart beat that does not originate at the sino-atrial node. These can be premature ventricular beats (coming from the ventricles) or premature atrial contractions (coming from the atria).
When they occur one at a time they are not considered significant.
EEG
The electroencephalogram or electrical recording of the brain. The EEG is a reflection of
the firing pattern of groups of neurons. The EEG is divided into'.frequency ranges. There is a
strong relationship between the EEG and sleep such that the EEG is a widely accepted measure of sleep and waking. Sleep is divided into stages based on EEG patterns as well as eye
movements (BOG) and muscle tone (EMG).
EMG
The electromyogram or electrical recording of the muscles. There are 2 EMG signals in the standard polysomnogram; the chin EMG and the leg EMG. The chin EMG is used to differentiate waking (high chin EMG) from R (low chin EMG). The leg EMGs are used to score movements during sleep.
End-tidal CO2
Measurement of the amount of carbon dioxide in the air expired from the lungs at the end of a breath. The air is analyzed on a breath-to-breath basis and provides the indication for a diagnosis of hypoventilation. It can also be used to detect apnea when the thermal sensor is
not working.
EOG
The electrooculogram or electrical recording of movement of the eyes. The eye is like a battery, with a positive charge at the front (cornea) and a negative charge at the back (retina). Movement can be recorded with electrodes near the eye because the signal will change when
the cornea or retina moves closer to the electrode. The EOG is used to determine when slow eye movements, rapid eye movements, reading eye movements and blinking occur.
Epoch
A set period of time. The epoch for scoring sleep stages is 30 seconds.
Esophageal manoetemr
A device used to measure the pressure in the esophagus. A tube is inserted in the nose and lowered into the stomach. It is then pulled back into the esophagus and a balloon is inflated. The pressure against the balloon measures the contraction of the muscles of the esophagus as well as the pressure in the chest. The pressure increases and decreases with the effort to breath.
Excessive fragmentary myoclonus (EFM)
A sleep study leg EMG finding consisting of frequent rapid bursts of activity scored during N sleep. The activity is often not associated with visible movements. EFM has not been associated with clinical consequences.
Eye blinks
Blinking of the eyes occurs during W and produces a distinctive BOG pattern. Eye blinks occur at a frequency of 0.5 to 2 Hz and are associated with a rapid upward movement of the eye.
Fibrillation
Rapid, irregular contraction of muscles, especially the muscles of the heart. In atrial fibrillation the muscles of the ventricle contract at an irregular rate and continue to pump blood.
Ventricular fibrillation is not associated with blood flow and is fatal if not reversed quickly.
Frequency
The number of cycles of a signal in a fixed period of time (usually I second). The number of cycles per second is the frequency in Hz (in honor of Heinrich Hertz). The frequency is the
inverse of duration (1/duration).
High frequency filter
A filter to reduce the amount of fast frequency noise in order to see slower frequency activity more clearly. For example, the high frequency filter is useful in reducing noise in the respiratory signals.
Hypnagogic foot tremor (HFT)
Bursts of leg muscle activity with a frequency of 0.3 to 4 Hz. A train of 4 bursts is needed to score HFT. Each burst lasts I /4 to 1 second. This may be a sleep study finding that does not relate to any clinical disorder.
Hypnagogic hypersynchrony (HH)
An EEG pattern associated with N I sleep in children.. It consists of high amplitude (up to 350mv) waves between 3 and 4.5 Hz best seen in the frontal. and central channels. It is seen .in 30% of infants at 3 months post term and is usually gone by 12 years of age.
Hypopnea
Partial closing of the airway or reduced air flow. Hypopneas do not meet the criteria for apnea. There are 2 definitions of hypopnea in the S M Manual. One definition is a 30% decrease of the
amplitude of the nasal pressure signal and a 4% oxygen desaturation. The second definition is a 50% decrease of the nasal pressure signal and either a 3% oxygen desaturation or an arousal.
Hypoventilation
Inadequate ventilation resulting in an increase of carbon dioxide. In adults this is defined by at least a 10 mm Hg increase in carbon dioxide compared to waking-levels. In children this is defined by a level of 50 mm Hg or greater lasting more than 25% of total sleep time. Two methods are used for measuring carbon dioxide during sleep: end-tidal measures the amount of carbon dioxide in the exhaled air, and transcutaneous measures the acidity of the surface of the skin after it has been warmed. Both measures are related to the amount of carbon dioxide 'm the blood.
Impedance
A measure of how much of a signal is lost when a sinusoidal wave form is passed through a circuit. Impedance is measured in Ohms (named after Georg Simon Ohm; the symbol is WΩ). High
impedance indicates that much of the signal is lost and the electrode is not in proper contact with the skin. For sleep studies, the electrode impedance should be less than 5,OOOΩ(5kΩ).
K complex
K complex waveform used in scoring N2. The K complex is a sharp wave with the first part negative
and the second part positive. It has duration of at least 0.5 seconds. It is largest in the frontal
channel. No amplitude criteria are given, but it must stand out from the background.
Limb movement (LM)
A burst of EMG activity in the leg channel with duration between 0.5 and 10 seconds. The amplitude must be at least 8μV. more than the baseline amplitude. The LM ends when the amplitude is 2 μV or less above baseline for at least 0.5 seconds.
Low amplitude mixed frequency (LAMP)
Low amplitude mixed frequency (LAMP) Background EEG activity during sleep with a mixture of frequencies with most waves between 4 and 7 Hz.
Low chin EMG tone
No amplitude measure is given for low chin EMG tone. The tone must be lower in R than in wake, but it may drop to the level of R at sleep onset. Low chin EMG tone is used in the
definition of R.
Low frequency Filter
A filter to reduce the amount of 'low frequency noise in order to see faster frequencies more clearly. The low frequency filter is useful in the EMG recordings.
Major body movement
Artifact from movement and muscle activity that makes it impossible to determine the sleep stage for more than half of an epoch. Special rules are used to assign a sleep stage to these epochs.
Mixed apnea
A type of apnea that begins as a central apnea and includes a portion with airway obstruction and respiratory effort. Mixed apneas last at least 10 seconds in adults.
The lowest point or trough of a waveform.
Narrow complex tachycardia
A series of at least 3 heart beats at a frequency of at least 100 beats per minute and with a QRS duration of no more than 0.12 seconds.
Nasal pressure transducer
A measure of airflow based on changes in the pressure in tubing that is placed in or near the nose. The nasal pressure signal is used to score Hypopneas. A square root transformation of the signal reduces the number of Hypopneas scored and is thought to improve accuracy.
Obstructive Apnea
A type of apnea with no airflow but continued effort to breathe. Obstructive apneas are caused by closing of the upp,er airway as the patient tries to breathe in. Obstructive apneas last at least 10 seconds in adults and 2 missed breaths in children.
Periodic breathing
At least 3 central apneas separated by no more than 20 seconds of normal breathing. Periodic breathing is scored in children but not in adults. It is similar to Cheyne Stokes breathing but does not have a crescendo-decrescendo pattern.
Phasic
A short lasting part of a recording arising from a tonic (long-lasting) background. The phasic
parts of R .have rapid eye movements and muscle twitches on a background of no eye movements and low chin EMG tone.
PLM Series
At least 4 limb movements each separated from the previous movement by at least 5 seconds but no more than 90 Seconds.
Posterior slow waves of youth (PSW)
Waveforms usually mixed in with the dominant posterior rhythm in children. The waves are 2.5 - 4.5 Hz and go away with eye opening and sleep onset. PSW is uncommon in children younger than 2 years, most common between the ages of 8 and 14, and are rarely seen in adults.
Pulse oximeter
A device that uses changes in the wavelength of blood in the capillaries to estimate the amount of oxygen in the blood. The signal averaging time must be less than 3 seconds. Oxygen desatu-
rations are used to score hypopnea and to provide an indicator of the severity of sleep apnea.
Rapid eye movements
Eye movements during waking and R that are sharply peaked, with the first part of the wave lasting less than 0.5 seconds. During W the eye movements occur as the patient scans the environment.
Reading eye movements
A distinctive pattern of eye movements that occur when scanning a page of text. The first part is slow as the eye tracks from left to right across the page. The second part is rapid as the eye moves to the beginning of the next line
REM sleep behavior disorder (RBD)
A disorder in which the patient acts out dreams, frequently resulting in injury The sleep study shows increased muscle activity 'in R.
Respiratory effort related arousals (RERAs)
A reduction of airflow that results in an arousal. RERAs do not meet the criteria for apnea or hypopnea. They last at least 10 seconds. Reduced air flow is best seen in the nasal pressure transducer; increasing effort is best seen in the esophageal manometer.
Respiratory inductance plethysmography (RIP)
A measure of respiratory effort that uses a coiled wire sewn into an elastic belt. A current is applied to the wire. When the patient breathes in, the wire uncoils and the frequency of the applied current is changed. The Rip provides an indirect measure of the volume of air in the lungs.
Rhythmic anterior theta (RAT)
Rhythmic 5 - 7 Hz EEG activity in the frontal channel used to score N1 sleep in children.
Rhythmic movement disorder (RMD)
Movement disorders more common in children and include head banging, body rocking and head rolling. The movements,can be recorded with EMG electrodes on the neck or shoulders. The movements have a minimum frequency of 0.5 Hz and a maximum frequency of 2 Hz. A sequence of at least 4 movements is required.
Sampling rate
The number of voltage measurements per second used to convert the continuous sleep study signals into a digital signal. The minimum sampling rate for EEG, EOG, EMG and ECG is 200 samples per second but 500 samples per second is desirable.
Sawtooth waves
Sharp or triangular waves with a frequency of 2 to 6 Hz usually largest in the central channels. The waves look like the teeth of a hand saw. They usually occur before a burst of rapid eye
movements in R.
Sino-atrial node
The heart's pacemaker located in the right atrium of the heart. All of the heart's cells can generate a heart beat, but the maximum blood flow is achieved when the sino-atrial node
paces the heart with a regular sinus rhythm. This allows the muscles to have a period of rest
(refractory period) between beats.
Sleep onset
In a sleep study, the time between lights out and the first epoch of any stage other than W
Sleep spindles
A train of waves lasting at least 0.5 seconds with a frequency of I I to 16 Hz, largest in the central leads. Sleep spindles are used in the scoring of N2. They are thought to be produced
by electrical feedback between the cortex and the thalamus.
Slow eye movements
Eye movements around sleep onset with the initial part lasting more than 0.5 seconds. Slow eye movements are used to score Nl in patients who do not have alpha rhythm.
Slow wave activity
EEG activity in the range of 0.5 to 2 Hz with amplitude from zenith to nadir of more than 75μV. Slow wave activity is used in the scoring of N3 sleep.
Sustained
In scoring cardiac arrhythmias during sleep, sustained tachycardia or bradycardia lasts at least 30 seconds.
Tachycardia - Sinus tachycardia
in sleep is defined as a heart rate faster than 90 beats per minute and lasting at least 30 seconds. Wide and narrow complex tachycardia’s have a rate faster than 100 beats
per minute and last at least 3 heart beats.
Thermal sensor
A measure of airflow based on changes in temperature. Air moving into the lungs is colder than air that has been warmed in the body and exhaled. The temperature change is related to the
amount of airflow, but not perfectly. Thermal sensor changes are used in the definition of apnea.
Theta activity
Activity in the range of 4 to 7 Hz.
Tonic
Background or long-lasting activity that provides a contrast to phasic activity. The tonic portions of R are periods with low chin EMG and L but no rapid eye movements or transient muscle activity.
Transcutaneous CO2
A measure of carbon dioxide in the blood that uses a heated probe to measure the pH of the skin. Transcutaneous carbon dioxide measures are used in the definition of hypoventilation.
Transient muscle activity
Brief bursts of EMG activity in the chin or leg EMG lasting less than 0.25 seconds. The bursts are usually associated with twitches during R. 
Vertex sharp waves
Sharp waves lasting less than 0.5 seconds largest in the central channel. They are used in the definition of Nl in patients who do not have alpha rhythm.
Waveform
The shape of a signal. The waveform can be sharp or rounded, regular or irregular, sinusoidal or triangular. Distinctive shapes are used in the definition of alpha rhythm and sawtooth waves.
Wide complex tachycardia
A series of at least 3 heart beats at a frequency of at least 100 beats per minute and with QRS duration of 0.12 seconds or longer.
Zenith
The highest point or peak of a waveform.