Sleep Disorder - Glossary

Front 1

AC Amplifier

Back 1

An amplifier designed to process relatively fast signal frequencies such as EEG, EOG, EMG, ECG. Has both High and Low Frequency filters.

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AC signal

Back 2

Alternating current signal that can either be negative or positive and are high frequency signals such as EEG or EMG waves.

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Actigraph

Back 3

A biomedical instrument for the measurement of body movement.

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Active Sleep

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A stage of sleep in neonates and infants equivalent to REM sleep in adults.

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Alpha Activity

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EEG waveform activity in the 8‐13 Hz (cycles per second) range. Considered as the “wake” state.

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Alpha‐Delta Sleep overriding/superimposing on delta/slow wave sleep.

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Alpha waves overriding/superimposing on delta/slow wave sleep.

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Alpha Intrusion

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Alpha waves overriding/superimposing on all other sleep stages.

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Alpha Rhythm

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EEG waveform on the 8‐13 Hz range. Considered as the “wake” state and seen predominately in the occipital regions of the brain.

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Alpha Sleep

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Stage of sleep considered to be “wake”

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Alpha Wave

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A type of brain wave detected by EEG and predominately originates from the occipital lobe during wakeful relaxation with the eyes closed. Alpha waves have a frequency range of 8‐12 Hz.

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Alternating Leg Muscle Activation (ALMA)

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Alternating Leg Muscle Activation (ALMA): A sleep disorder where there is repetitive movement in the legs that alternates between them.

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Amplifier

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A device that changes the amplitude of a signal.

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Amplifier Calibration

Back 13

A test to determine the integrity of the recording system.

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Anterior Tibialis

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A muscle that originates in the upper two‐thirds of the lateral surface of the tibia.

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Apnea

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An interruption of airflow lasting at least 10 seconds in adults or the equivalent of 2 breaths is children.

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Apnea‐Hypopnea Index (AHI)

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The total number of apneic and hypopneic episodes per hour of sleep.

Front 17

Apnea Index (AI):

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The total number of apneic episodes (obstructive, mixed, and central) per hour of sleep.

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Arousal

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An interruption in sleep continuity

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Arousal Index

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The total number of EEG arousals per hour of recorded sleep time.

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Artifact

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Anything not naturally made or present; an unwanted or irrelevant signal

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Atria

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An anatomical structure of the heart.

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Asystole

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Interruption of cardiac rhythm lasting more than 3 seconds

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Atonic

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Without normal tension or tone (muscle)

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Atrial Fibrillation

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Irregular ventricular rhythm associated with replacement of consistent P waves by rapid electrical oscillations

Front 25

Atrial Flutter

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An abnormal heart rhythm that occurs in the atria of the heart.

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Atrioventricular Node (AV Node)

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Atrioventricular Node (AV Node): A part of the electrical control system of the heart that coordinates heart rate. It electrically connects atrial and ventricular chambers.

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Attenuation

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The gradual loss in intensity of waves and signals.

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AV Block

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The impairment of the conduction between the atria and ventricles of the heart.

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Beta Rhythm

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EEG waveform with a frequency of 13 Hz‐30 Hz (cycles per second).

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Bigeminy

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An abnormal arrhythmia of the heart when beats occur every other concurrent beat.

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Bio‐Calibrations

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A series of simple maneuvers performed by the patient prior to ”lights out” and again at “lights on” to ensure tracing reliability on the sleep study.

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Bi‐Polar Derivation

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Signal obtained by comparing voltages from two exploring electrodes.

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B‐PAP

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Bi‐level pressure device used to treat sleep apnea, including EPAP for exhalation and a higher IPAP for inhalation.

Front 38

Body Mass Index (BMI)

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A calculation used to estimate a healthy body weight based on a person’s height.

Front 40

Body Movement

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Any event in which the patient moves any large group of muscles causing movement artifact on the Polysomnogram.

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Bradycardia

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Sustained heart rate less than 40 beats per minute

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Brain Waves

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Electrical activity of the brain.

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Bruxism

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Grinding or clenching of the teeth during sleep that is often associated with an arousal

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Bundle Branches

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Three branches from the bundle of HIS in the heart that run along the

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inter‐ventricular septum.

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Calibration

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A process of testing and adjusting all diagnostic equipment in response to varying voltages of a known value to ensure the integrity of the recorded signals.

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Canthus

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The corner of the eye.

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Capnograph

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Instrument used to measure the carbon dioxide concentration at the end of expiration.

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Cardiac Arrest

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A complete cessation of beating in the heart requiring immediate medical attention.

Front 54

Cataplexy

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Refers to a sudden loss of muscle tone usually associated with a strong emotional stimulus. Appears to be a sudden onset of REM‐related muscle atonia but without loss of consciousness

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Central Apnea

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A period of no airflow or respiratory effort for at least ten seconds during sleep.

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Central Nervous System (CNS)

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The part of the human body involving the brain, spinal cord, and nerves.

Front 57

Central Sleep Apnea

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A disorder characterized by the presence of central apneas.

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Channel

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Refers to a single display of electrical signals on a Polysomnogram displaying certain desired biological potentials.

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Cheyne‐Stokes Respiration

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A breathing pattern characterized by regular “crescendodecrescendo” fluctuations in respiratory rate and tidal volume

Front 60

Chin EMG

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The channel in the recorded PSG displaying a recording of muscle activity from the chin.

Front 61

Circadian Rhythm

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A daily fluctuation of physiological or behavioral functions, including sleep‐wake states generally tied to the 24 hour daily dark‐light cycle, but sometimes at a measurably different periodicity when light‐dark and other time cues are removed

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Common Mode Rejection

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A function of a differential amplifier by which identical signals received through both of its input terminals are greatly attenuated. Primary method of eliminating undesirable electrical interference within bio‐electrical potential recordings.

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Confusional Arousal

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Occasional thrashings or inconsolable crying among children that are characterized by movements in bed.

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Consensus

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Specified agreement of appropriateness amongst a minimum of 8 individuals using RAND/UCLA methods.

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Cycles per Second (cps)

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The number of “peaks” (EEG waves) occurring in a one second time frame.

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DC Amplifier

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An amplifier designed to process relatively slow/low signal frequencies such as oximeter.

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Deep Sleep

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Also known as Stage 3, slow wave sleep, restorative sleep; Delta sleep.

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Delayed Sleep Phase

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A condition where one’s internal clock is moved back (delayed) in a given 24 hour sleep‐wake cycle.

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Delta Rhythm

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EEG rhythm consisting of 1‐4Hz

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Delta Wave

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EEG waveform with a frequency of 0.5‐2 Hz with an amplitude of at least 76 μV from peak to peak in at least 20% of the epoch.

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Diaphragm

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The large muscle attached to the rib cage at the bottom of the chest and top of the abdomen. Inhalation is caused by the diaphragm contracting, and exhalation occurs as the diaphragm relaxes.

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Differential Amplifier

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An amplifier whose output is proportional to the voltage differences between two incoming signals. Also known as AC amplifier.

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Diurnal

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Happening in the daytime

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Dominant Posterior Rhythm

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Age appropriate frequency of wakefulness or attention with eye closed and attenuates with eye opening or attention.

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Dopamine

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A chemical produced in the brain that is responsible for arousal of the cortex, movement, and responsiveness.

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Double Referencing

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Using cables to connect two reference leads to each other in order to decrease or eliminate artifact by increasing common mode rejection ratio.

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Drowsiness

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State of subtle wakefulness prior to sleep onset.

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Duration

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An amount of time or a particular time interval.

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Electrode

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An electrically‐conductive wire or device applied to the scalp or body to transmit bio‐electrical potentials to the amplifier.

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Electrode Impedance

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Resistance to the flow of electricity from the scalp or body to the sensor or electrode. Optimal impedance levels should be below 5 Kohms (5000 ohms) to produce a high quality recording.

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Electrode Popping

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An artifact characterized by an occasional brief burst of 60Hz activity.

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Electroencephalogram (EEG)

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A recording of electrical activity of the brain by means of electrodes placed on the surface of the head. Use to score stages of sleep.

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Electromyogram (EMG)

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A recording of electrical activity from the muscular system by means of surface electrodes placed in designated areas during sleep (Chin, anterior tibialis).

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Electro‐oculogram (EOG)

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A recording of voltage changes resulting from shifts in position of the ocular globes by means of electrodes placed near the eyes to record movement of the eyeballs.

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End‐Tidal Carbon Dioxide (EtCO2)

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Carbon dioxide value usually determined at the nares by an infrared carbon dioxide gas analyzer. The value reflects the alveolar or pulmonary arterial blood carbon dioxide level.

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Enuresis

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Enuresis: The inability to control urination.

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Epoch

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Corresponds to a page of the Polysomnogram. Typically an epoch is 30 seconds in duration.

Front 88

Epworth Sleepiness Scale (ESS)

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A short questionnaire used to measure daytime sleepiness.

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Esophageal Balloon

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A device inserted into the esophagus used to measure small changes in airway resistance.

Front 90

Esophageal Pressure

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Esophageal Pressure: The amount of pressure produced by the esophagus that is measured by inserting a catheter into the esophagus. This helps to detect Upper Airway Resistance.

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Excessive daytime Sleepiness (EDS

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Excessive daytime Sleepiness (EDS) : A subjective report of maintaining wakefulness and a rapid initiation into sleep when the individual is sedentary. Most commonly occurs during the daytime however excessive sleepiness may be present at night in an individual who has major sleep period during the daytime.

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Excessive Fragmentary Myoclonus:

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Limb EMG activity of a specified frequency and duration often unassociated with visible movement; not a defined disorder

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Exploring Electrode

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Exploring Electrode: An electrode or sensor used to detect electrical activity in a specified area of the head or body.

Front 94

Eye Blinks

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EOG events consisting of conjugate vertical eye movements at a frequency of 0.5‐2 Hz present in wakefulness with the eyes open or closed.

Front 95

Fall Time

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Fall Time: The amount of time it takes for a calibration wave to fall from peak to 37% of peak.

Front 96

Filter

Back 96

A feature of an amplifier which limits the range of frequencies allowed to pass through the amplifier. Filters seen during a PSG include: High Frequency Filters (also known as Low Pass Filters), Low Frequency Filters (also known as High Pass Filters), and 61 Hz or Notch Filters.

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First Degree AV Block

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PR interval greater than 0.20 sec

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First Night Effect

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Reduced quality compared to that which would be expected in the subject’s usual sleeping environment without recording equipment. Habitation to the laboratory setting is found by the second night of recording.

Front 99

Fragmentary Myoclonus

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Very brief and often times high amplitude leg movements.

Front 100

Frequency

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Measured in cycles per second (cps) or Hertz (Hz), the number of times a wave oscillates in one second.

Front 101

Ground

Back 101

A common reference for all electrodes to use as a measurement tool for voltage differences in Polysomnography.

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Guideline

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A recommendation based on level 2 evidence or a consensus of level 4 evidence.

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Heart Rate

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The number of heartbeats per unit of time – typically expressed as beats per minute. (BPM)

Front 104

Hertz (Hz)

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A unit of frequency; preferred to the synonym, cycles per second.

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High Frequency Filter

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A tool or device on a PSG which sets a limitation to the high frequency signals that are allowed to pass through the amplifier.

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High Impedances

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Increased resistance to the flow of electricity, resulting in poor signal tracings.

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Histamine

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A chemical produced in the brain that is responsible for activation of the cortex helping to maintain wakefulness.

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Histogram

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A display of sleep stages achieved throughout the recorded sleep period.

Front 109

Home Sleep Study

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Also referred to as a Type 3 sleep study. It is performed in the patient’s home and monitored at a remote location.

Front 110

Humidification

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The process of adding moisture (usually heated) to supplemental oxygen or PAP to increase compliance and decrease side effects such as upper airway dryness.

Front 111

Hypercapnia

Back 111

Excessive CO2 levels in the blood.

Front 112

Hypersomnia

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Excessive sleepiness; deep or prolonged major sleep period; may be associated with difficulty awakening.

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Hypertension

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Also known as high blood pressure which can lead to a variety of health complications.

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Hyperventilation

Back 114

Hyperventilation: Period of increased PCO2 greater than 50 mmHg in children or PaCO3 greater than or equal to 10 mmHg in adults.

Front 115

Hypnagogic

Back 115

Occurrence of an event during the transition from wakefulness to sleep.

Front 116

Hypnagogic Foot Tremor

Back 116

Trains of EMG activity of the lower limb with a specified frequency; not a defined disorder.

Front 117

Hypnagogic Hypersynchrony

Back 117

Paroxysmal runs or bursts of diffuse high amplitude sinusoidal 3‐4.5 Hz waves of 75‐350 μV amplitude that begins abruptly, is widely dispersed, but often maximal over the frontal and central regions.

Front 118

Hypnagogic imagery (hallucinations)

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Vivid sensory images occurring at sleep onset, but particularly vivid with sleep‐onset REM periods. A feature of narcoleptic naps when the onset occurs with REM sleep.

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Hypnopompic

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Occurrences of an event during the transition from sleep to wakefulness.

Front 120

Hypopnea

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An episode of shallow breathing (Diminished airflow) during sleep lasting 11 seconds or longer; usually associated with a fall in blood oxygen saturation value.

Front 121

Hypoventilation

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Period of increased PCO2 >50mmHg in children or PaCO2 ≥10mmHg in adults.

Front 122

Hypoxemia

Back 122

Abnormally low blood oxygen levels

Front 123

Impedance

Back 123

Resistance to the flow of electricity. During the recording of a Polysomnogram, EEG electrode impedances should be kept below 5000 Ohms.

Front 124

Impedance Meter

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The device that measures electrode impedances.

Front 125

Inductive Plethsmography

Back 125

A mechanism used to measure respiratory effort involving magnetic properties of a coil of wire. A change in current flowing through this coil of wire induces an electromotive force. (EMF)

Front 126

Inion

Back 126

An anatomical landmark on the back of the head where the occipital bone protrudes out from the skull that is used in the International 10‐20 System of Electrode Placement used to locate measured electrode sites.

Front 127

Input

Back 127

A location for signals to enter the diagnostic recording equipment.

Front 128

Insomnia

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Difficulty initiating and/or maintaining sleep.

Front 129

Intercostal EMG

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An EMG channel used to measure respiratory effort by detecting activity in the intercostal muscles.

Front 130

Interface

Back 130

A device used to assist in the connection between two electronic devices.

Front 131

International 10/20 System of Electrode Placement

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A system of measuring standards of EEG electrode placement which utilizes specified anatomical landmarks and measurement percentages to locate EEG electrode placement sites.

Front 132

Internodal Pathways

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Tracts of cardiac cells carrying electrical impulses between the sinoatrial node and the atrioventricular node of the heart. These tracts allow distribution of electrical impulses across the atria allowing for depolarization of these cardiac chambers.

Front 133

Jet Lag Disorder

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A sleep disorder characterized by a disturbance to sleep induced by travel to a new time zone. Traveling from West to East seems to have a greater negative impact on the circadian cycle.

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K Complex

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A sharp, biphasic EEG wave followed by a high voltage slow‐wave. The complex duration is at least 0.5 seconds and may be accompanied by a sleep spindle

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Latency

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The period of time between sleep stages or recorded events.

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Lead

Back 136

The wire that connects an electrode or sensor to the head box.

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Leg Movement

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An event recorded during a PSG which may indicate a disturbance to sleep.

Front 138

Light Sleep

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A term used to describe sleep stages N1 and N2 as a person may be easier to awaken.

Front 139

Light Therapy

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A treatment commonly used to treat insomnia and certain other circadian rhythm disorders that is done by exposing the eyes to additional levels of light in the morning hours to boost the circadian rhythm.

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Lights Off

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A notation made on the sleep study indicating the start of the recording time.

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Lights On

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Lights On: A notation made on the sleep study indicating the end of the recording time.

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LOC

Back 142

Abbreviation for Left outer canthus of the eye.

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Low Amplitude, Mixed Frequency Activity

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EEG pattern of low amplitude in the theta range

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Low Chin EMG tone

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Chin EMG amplitude at the lowest level of the entire study.

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Low Frequency Filter

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A device used to reduce the amplitude of slower frequency filter as they pass through an amplifier

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Maintenance of Wakefulness Test (MWT)

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A series of measurements to assess wakefulness in a darkened room while in a semi‐reclined position. Long latencies to sleep are indicative of the ability to remain awake. Most useful for assessing the effects of medications upon the ability to remain awake.

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Masseter

Back 147

A muscle of the jaw and chin area.

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Mastoid

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Used as a location for the reference electrodes M1 and M2 and is the lower part of the bone behind the ears.

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Material Safety Data Sheet (MSDS)

Back 149

Information provided by the manufacturer of a potentially hazardous product which discloses proper use, disposal, and potential dangers.

Front 150

Mechanical Baseline

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The vertical placement of a pen when the power to the amplifier is turned off.

Front 151

Melatonin

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A hormone secreted by the pineal gland which affects wakefulness.

Front 152

Micro‐arousal

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A brief EEG arousal or a partial awakening from sleep.

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Micro‐sleep

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A brief interlude of sleep during a wake state

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Microvolt (μV)

Back 154

An electrical term referring to one millionth of a volt. This is the unit for measuring the amplitude of EEG signals.

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Mixed Apnea

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A complete cessation of airflow for at least 10 seconds that begins as a central apnea (no associated respiratory effort) and ends as an obstructive apnea (respiratory effort).

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Montage

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The particular arrangement by which a number of derivations are displayed simultaneously in a Polysomnogram.

Front 157

Movement Arousal (MA)

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A body movement associated with an EEG pattern of arousal or a full awakening; a sleep scoring variable.

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Movement Artifact

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An unwanted signal caused by movements from the patient.

Front 159

Movement Time (MT)

Back 159

EEG and EOG tracings are obscured for more than half the scoring epoch because of movement. The preceding and succeeding epochs are sleep.

Front 160

Multiple Sleep Latency Test (MSLT

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A series of measurements whereby subjects are allowed a fixed number of opportunities to fall asleep during their customary awake period. Excessive sleepiness is characterized by short latencies. Long latencies are helpful in distinguishing physical tiredness or fatigue from true sleepiness.

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Muscle Tone

Back 161

The level of tension in a muscle.

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Myocardial Infarction (MI)

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More commonly referred to as a heart attack.

Front 163

Myoclonus

Back 163

Muscle contractions in the form of abrupt jerks or twitches.

Front 164

Narcolepsy

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A chronic sleep disorder characterized by excessive daytime sleepiness (EDS) in which a person experiences extreme fatigue and may fall asleep at inappropriate times such as while driving.

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Narrow Complex Tachycardia

Back 165

Sustained cardiac rhythm of 3 consecutive beats at a rate >100 beats and QRS duration <120 msec.

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Nasal Airflow

Back 166

Usually recorded by a pressure transducer, thermistor, thermocouple, or similar recording device, nasal airflow is a recording of respirations by measuring inspiratory and expiratory airflow through the nose.

Front 167

Nasion

Back 167

An anatomical landmark used in the International 10‐20 System of Electrode Placement that is located on the top or bridge of the nose where the forehead and nose meet.

Front 168

Neurotransmitters

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Chemicals in the brain that allow for the exchange of impulses from one neuron to the next.

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Nightmare

Back 169

A term used to denote an unpleasant and frightening dream that usually occurs in REM sleep.

Front 170

Nightmare Disorder

Back 170

A sleep disorder characterized by the occurrence of frequent nightmares.

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Nocturnal

Back 171

A term referring to events that occur during the night.

Front 172

Nocturnal Confusion

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Occurs during, immediately before, or immediately after nighttime sleep.

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Nocturnal sleep‐related eating disorder

Back 173

A sleep disorder when a person gets up during the night and eats while sleeping.

Front 174

Normal Sinus Rhythm (NSR)

Back 174

An EKG rhythm characterized by a normal heart rate and rhythm wilh all wave intervals in the normal ranges.

Front 175

Notch Filter

Back 175

A frequency filter used for a small range of frequencies from 50‐60 Hz. It helps to eliminate AC line frequency interference.

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Oculogram

Back 176

Tracings derived from the recording and detection of eye movement activity.

Front 177

“Ondine’s Curse”

Back 177

Adequate ventilation while awake, but severe hypoventilation or apnea when asleep

Front 178

Ohm

Back 178

Unit of electrical measurement of impedances.

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Outer Canthus

Back 179

Located at the outside area of the eye where the eyelids meet.

Front 180

Output signals

Back 180

Electrical signals which have passed through the amplifier and are displayed on a PSG.

Front 181

Oximeter

Back 181

Also known as pulse oximeter, it is a device used to estimate oxygen saturation levels in the blood.

Front 182

Oxygen Desaturation

Back 182

A temporary decrease in oxygen levels in the blood.

Front 183

Oxygen Saturation

Back 183

The measure of oxygen carried by the hemoglobin in the blood.

Front 184

Paradoxical Sleep

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Synonymous with REM sleep, the preferred term.

Front 185

Parasomnia

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Disorder of arousal, partial arousal, or sleep stage transition.

Front 186

Paroxysmal Nocturnal Dyspnea

Back 186

Respiratory distress and shortness of breath due to pulmonary edema, which appears suddenly and often awakens the sleeper.

Front 187

Patient Chart

Back 187

The file containing all patient information such as initial questionnaire, medical history, medications, etc. and can either be maintained in paper form or digitally.

Front 188

Patient Questionnaire

Back 188

An in‐depth questionnaire used to determine the severity of a patient’s condition before they have a sleep study performed.

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Peak

Back 189

The point of a wave that is highest or lowest in amplitude. Alternating current signals are measured from peak to peak.

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Pediatric Sleep Medicine

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Refers to an area of sleep medicine that focuses on children under the age of 18.

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Pen Blocking

Back 191

An artifact caused when there is a high gain setting which causes the signal to reach beyond the upper and/or lower channel parameters.

Front 192

Periodic Breathing

Back 192

Refers to episodes of repetitive apneas.

Front 193

Periodic Limb Movement (PLM)

Back 193

A rapid, partial flexion of the foot at the ankle, extension of the big toe, and the partial flexion of the knee and hip that occurs during sleep. The movements occur with a periodicity of 5‐90 seconds in a pattern lasting 0.5‐11 seconds in duration and amplitude increase of 8μv.

Front 194

Periodic Movements of Sleep (PMS)

Back 194

Same as Period Limb Movement

Front 195

Phasic Event (activity)

Back 195

Brain, muscle or autonomic event of a brief and episodic nature occurring in sleep; characteristic of REM sleep, such as eye movements or muscle twitches.

Front 196

PLM/Arousal Index

Back 196

The number of sleep‐related periodic limb movements per hour of

Front 197

PLM Index

Back 197

The number of periodic limb movements per hour of total sleep time

Front 198

Polarity

Back 198

The positive or negative orientation of electrical signal.

Front 199

Polysomnogram (PSG)

Back 199

The continuous and simultaneous recording of physiological variables during sleep (EEG, EOG, EMG‐the three basic stage scoring parameters) EKG, respiratory airflow, respiratory movements, limb movements, and other physiological variables.

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Potential

Back 200

An electrical signal or voltage.

Front 201

Preauricular Point

Back 201

An anatomical landmark used in the International 10‐20 Electrode Placement System. It is a small notch located at the midpoint of the ear in front of the opening of the ear canal.

Front 202

Premature Atrial Contraction (PAC)

Back 202

Type of premature or irregular heart beat which occur in the upper two chambers of the heart or atria.

Front 203

Premature Ventricular Contraction (PVC)

Back 203

An EKG rhythm characterized by a wide, irregular QRS complex.

Front 204

Pressure Transducer

Back 204

A monitoring device that uses pressure from expired air to detect airflow.

Front 205

Pretest Questionnaire

Back 205

A brief questionnaire relating to a patient’s sleep‐related events the day of a sleep study.

Front 206

Purkinje Fibers

Back 206

Located in the inner ventricular walls of the heart, these fibers conduct an electrical impulse that enables the heart to contract in a coordinated fashion.

Front 207

Quality Control

Back 207

A group of practice parameters designed to improve quality of specific procedures in the sleep center.

Front 208

Quiet Sleep

Back 208

The term now referred to as NREM sleep which was primarily used to describe the sleep of infants.

Front 209

Reading Eye Movement

Back 209

EOG events of conjugate eye movements trains with a rapid phase following a slow phase in the opposite direction.

Front 210

Rebound Sleep

Back 210

Sleep after periods of sleep deprivation. This usually consists of decreased sleep latency, and increased N3 sleep and stage R sleep.

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Reference Electrode

Back 211

An electrode or sensor used as a standard when comparing potentials from an exploring electrode.

Front 212

REM Behavior Disorder

Back 212

Parasomnia with intermittent loss of atonia during REM and associated with potentially harmful movements as subject enacts the dreams.

Front 213

REM Density

Back 213

A function that expresses the frequency of eye movements per unit time during sleep stage REM

Front 214

REM Sleep Latency

Back 214

The interval from sleep onset to the first appearance of stage REM sleep in the sleep episode.

Front 215

REM‐Sleep Rebound (recovery)

Back 215

REM‐Sleep Rebound (recovery): Lengthening and increase in frequency and density of REM sleep episodes which result in a increase in REM‐sleep percent above baseline. REM‐sleep rebound follows REM‐sleep deprivation once the deprivation influence is removed.

Front 216

Re‐referencing

Back 216

The process of referencing to another electrode in order to eliminate an artifact.

Front 217

Respiratory Belt

Back 217

A belt containing a sensor that is secured around the diaphragm of the patient to measure respiratory effort.

Front 218

Respiratory Disturbance Index (RDI)

Back 218

Respiratory Disturbance Index (RDI): The number of apneas (obstructive, mixed, and central) and hypopneas per hour of total sleep time. Also termed Apnea‐Hypopnea Index (AHI)

Front 219

Respiratory Effort Related Arousal (RERA)

Back 219

Breathing pattern lasting at least 11 seconds that does not meet a hypopnea or apnea criteria that results in an arousal from increasing respirations.

Front 220

Restless Leg Syndrome (RLS)

Back 220

A common sleep disorder characterized by a creepycrawly sensation in the legs that usually occurs when the patient is awake and notmoving.

Front 221

Reticular Activating System (RAS)

Back 221

A system in the brain causing wakefulness and alertness.

Front 222

Rhythmic Movement Disorder

Back 222

Repetitive rhythmic movements occurring with drowsiness or sleep involving large muscle groups.

Front 223

Rhythmic Theta Activity

Back 223

Runs of 6‐7 Hz rhythmic theta activity best seen in the frontal or frontocentral regions.

Front 224

Rise Time

Back 224

The amount of time for a calibration signal to rise from baseline to 63% of the peak.

Front 225

ROC

Back 225

The name of the EOG electrode site located near the right eye.

Front 226

Sampling Rate

Back 226

The designated number of bits recorded per second in a channel.

Front 227

SaO2

Back 227

The amount of oxygen in the blood as read by an arterial blood gas.

Front 228

Sawtooth Waves

Back 228

A form of theta rhythm that occurs during REM sleep and is characterized by a notched appearance in the waveform. Occurs in bursts lasting up to 11 seconds in duration

Front 229

Second Degree AV Block, Type I

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Aka Mobitz I, Encroach – Progressive prolongation of PR interval with dropped beats, the PR interval gets longer and longer, finally one beat drops.

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Second Degree AV Block, Type II

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Aka Mobitz II – PR interval remains unchanged prior to the P wave which suddenly fails to conduct to the ventricles.

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Sedatives

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A class of drugs designed to calm and reduce anxiety or excitement allowing a patient to fall asleep.

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Seizure Activity

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EEG activity which indicates the occurrence of a seizure.

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Sensitivity Setting: A setting on the Polysomnograph which adjusts the height of the

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Sensitivity: The ratio of signal input to the resulting wave which is usually measured in μV/mm.

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Sensitivity Setting

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A setting on the Polysomnograph which adjusts the height of the wave.

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Serotonin

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A chemical produced in the brain that affects mood, appetite, aggression, body temperature, and sleep.

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Signal

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An electrical impulse or voltage.

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Sinoatrial Node (SA Node)

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Impulse generating tissue located in the right atrium of the heart.

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Sinus Arrhythmia

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A naturally occurring variation in heart rate that occurs during a breathing cycle.

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Sinus Bradycardia

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A heart rhythm that originates from the sinus node and has a rate of under 60 beats per minute.

Front 240

Sinus Tachycardia

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A heart rhythm with elevated rate of impulses originating from the Sinoatrial node with a rate greater than 100 beats/minute in an average adult.

Front 241

Sixty Hertz Filter

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A filter pointed specifically at electrical activity in the 59‐61Hz range to eliminate or attenuate 60Hz activity.

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Sleep Architecture

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The non‐REM / REM sleep stage and cycle infrastructure of sleep

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Sleep Cycle

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A complete NREM‐REM cycle.

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Sleep Debt

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The cumulative effort of not getting enough sleep. A large sleep debt may lead to mental and/or physical fatigue.

Front 245

Sleep Diary

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The record of an individual’s sleeping and waking times with related information, usually over a period of several weeks.

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Sleep Disorders

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A medical disorder of the sleep pattern. Some sleep disorders are serious enough to interfere with normal physical, mental, and emotional functioning.

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Sleep Deprivation

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A condition of having too little sleep. It can be chronic or acute.

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Sleep Efficiency

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The proportion of sleep in the episode potentially filled by sleep. The ratio of total sleep time to time in bed expressed as a %.

Front 249

Sleep Hygiene

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Conditions and practice that promote continuous and effective sleep.

Front 250

Sleep Latency

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The duration of time measured from “lights out’, or bedtime to the onset of sleep.

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Sleep Log

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A diary of an individual’s time in bed that includes estimated total sleep time, lights out time, lights on time, and daily activities.

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Sleep Onset REM Period (SOREM)

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Sleep Onset: The transition from awake to sleep.

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Sleep Onset REM Period (SOREM)

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Sleep Onset REM Period (SOREM): The beginning of sleep by entrance directly into

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stage REM sleep. The onset of REM sleep occurs within 10 minutes of sleep onset.

Front 256

Sleep Paralysis

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Sleep Paralysis: Immobility of the body that occurs in the transition from sleep to

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wakefulness which is a partial manifestation of REM sleep.

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Sleep Related Erections (SRE’s)

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Sleep Related Erections (SRE’s): The natural periodic cycle of penile erections that

Back 259

occur during sleep, typically associated with REM sleep. Consists of four phases: T‐up

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(ascending tumescence), T‐mas (plateau maximal tumescence), T‐down

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(detumescence), and T‐zero (no tumescence) Preferred term over NPT)

Front 262

Sleep Stages

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Sleep Stages: Periods of sleep with distinct characteristics seen in the EEG, EOG, and

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EMG channels which includes: N1 sleep, N2 sleep, N3 sleep, and R.

Front 264

Sleep Start

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Sleep Start: Also known as a hypnic jerk, this event is characterized by a sudden jerk or

Back 265

movement at sleep onset resulting in wakefulness and often alarm.

Front 266

Sleeptalking (Somniloqui)

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Sleeptalking (Somniloqui): Talking in sleep that usually occurs during stage REM sleep,

Back 267

at which time it represents a motor breakthrough of dream speech.

Front 268

Sleep Terror

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Sleep Terror: A sleep disorder occurring during stage N3 sleep in which the patient

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jumps out of bed with a loud scream and exhibits dangerous or threatening behaviors.

Front 270

Sleep‐Wake Cycle (SWS)

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Sleep‐Wake Cycle (SWS): The clock hour relationships of the major sleep and wake

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episodes in the 24 hour cycle.

Front 272

Sleepwalking (Somnambulism)

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Sleepwalking (Somnambulism): Movement disorder, usually occurring in delta sleep.

Front 273

Slow Eye Movements:

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Slow Eye Movements: Conjugate regular sinusoidal eye movements with initial

Back 274

deflection >500 msec.

Front 275

Slow Wave Artifact: An unwanted low frequency often caused by sweat.

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Slow Wave: An EEG wave that is at least 75μV and is 0.5‐2Hz.

Front 276

Slow Wave Artifact

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Slow Wave Artifact: An unwanted low frequency often caused by sweat.

Front 277

Snore Artifact

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Snore Artifact: A high frequency artifact caused by vibrations in the upper airway. This

Back 278

is usually seen in the chin EMG, EEG’s and EOG’s.

Front 279

Snore Sensor

Back 279

Snore Sensor: A device that reads vibrations from the upper airway and is recorded in a

Back 280

Polysomnogram.

Front 281

Split Night Study

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Split Night Study: A type of sleep study performed in which the first half of the night is

Back 282

diagnostic and the second half is therapeutic with a PAP titration.

Front 283

SpO2 : Oxy‐hemoglobin Saturation

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SpO2: The amount of oxygen in the blood as read by a pulse oximeter.

Front 284

Stage N1

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Stage N1: A stage of NREM sleep occurring during the transition from wake to sleep and

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normally comprises 2‐5% of the total sleep period.

Front 286

Stage N2

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Stage N2: A stage of NREM sleep characterized by sleep spindles and K complexes

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comprising of approximately 45‐55% of total sleep period.

Front 288

Stage N3

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Stage N3: A stage of NREM sleep defined by at least 20% of the 30 second epoch

Back 289

consisting of EEG slow waves with frequencies less than 2Hz and amplitudes greater

Back 290

than 75μV. This stage of sleep comprises up to 40% of the total sleep period in normal

Back 291

children and 13‐22% of the total sleep period in normal adults.

Front 292

Stage R

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Stage R: The stage of sleep during which the brain activity is similar to wakefulness, but

Back 293

muscle tone is absent. Stage R or REM sleep is characterized by the presence of rapid

Back 294

eye movements, and is the stage in which dreaming usually occurs. This stage of sleep

Back 295

comprises 20‐25% of total sleep period.

Front 296

Stage W:

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Stage W: An epoch score in which the patient is awake. It is characterized by alpha

Back 297

activity in the occipital EEG channels, eye blinks, high amplitude chin EMG, and muscle

Back 298

movements.

Front 299

Standard

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Standard: Recommendation based on level 1 evidence or overwhelming level 3

Back 300

evidence.

Front 301

Supplemental Oxygen

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Supplemental Oxygen: Additional oxygen delivered to the patient through nasal

Back 302

cannula.

Front 303

Suprachiasmatic Nucleus (SCN)

Back 303

Suprachiasmatic Nucleus (SCN): A structure in the brain responsible for the 24 hour

Back 304

circadian rhythm.

Front 305

Sweat Artifact

Back 305

Sweat Artifact: A slow wave artifact caused by excessive sweating from the patient.

Front 306

Tachycardia

Back 306

Tachycardia: An EKG arrhythmia characterized by a rapid heart rate, usually defined by

Back 307

a pulse rate of over 100 bpm.

Front 308

Thalamus

Back 308

Thalamus: The structure in the brain responsible for relaying certain sensory

Back 309

information from the body to different parts of the brain.

Front 310

Thermistor

Back 310

Thermistor: A sensor which measures changes in temperature resulting from a

Back 311

patient’s inhalations and exhalations.

Front 312

Theta Rhythm

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Theta Rhythm: EEG rhythm of 4‐8 Hz activity.

Front 313

Third Degree (Complete) AV Block

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Third Degree (Complete) AV Block: No association between P waves and QRS

Back 314

complexes.

Front 315

Tidal Volume

Back 315

Tidal Volume: The estimated volume of air passed in and out of the lungs in a breath,

Back 316

usually measured in liters.

Front 317

Time Axis

Back 317

Time Axis: The horizontal time line of the Polysomnogram.

Front 318

Time Constant

Back 318

Time Constant: The fall time of a calibration wave to 37% of its amplitude.

Front 319

Titration

Back 319

Titration: A term referring to a steady increase in CPAP levels or oxygen flow applied

Back 320

during a sleep study to determine the optimal level of treatment.

Front 321

Tolerance

Back 321

Tolerance: The patient’s ability to use a treatment such as CPAP without additional

Back 322

disturbances to sleep.

Front 323

Tonic

Back 323

Tonic: Continuous EMG or EEG events, usually referring to activity during REM sleep.

Front 324

Tonic REM

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Tonic REM: Periods of stage R in which no eye movements occur.

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Total Recording Time (TRT)

Back 325

Total Recording Time (TRT): The duration of time from sleep onset to final awakening.

Back 326

In addition to total sleep time, it is comprised of the time taken up by wake periods and

Back 327

movement time until wake‐up. AKA: Time in bed.

Front 328

Total Sleep Time (TST)

Back 328

Total Sleep Time (TST): The amount of actual sleep time in a recording period

Front 329

Total Wake Time (TWT)

Back 329

Total Wake Time (TWT): The amount of time the patient spends awake during the

Back 330

recording time of the sleep study

Front 331

Tracé alternant

Back 331

Tracé alternant: EEG pattern of sleeping newborns, characterized by bursts of slow

Back 332

waves, at times intermixed with sharp waves, and intervening periods of relative

Back 333

quiescence with extreme low‐amplitude activity.

Front 334

Transducer

Back 334

Transducer: A device that converts energy from one form to another.

Front 335

Transient Muscle Activity

Back 335

Transient Muscle Activity: EMG activity with a duration of <0.25 seconds seen with low

Back 336

EMG tone in the chin or anterior tibial EMG derivations and in the EEG or EOG

Back 337

derivations (indicating cranial nerve innervated muscle activity) associated with rapid

Back 338

eye movements.

Front 339

Trigeminy

Back 339

Trigeminy: A cardiac arrhythmia identified when every third beat of a cardiac rhythm is

Back 340

a Premature Ventricular Contraction (PVC).

Front 341

Universal Precautions

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Universal Precautions: A group of practices such as hand washing that reduce or stop

Back 342

the spread of infection.

Front 343

Upper Airway

Back 343

Upper Airway: The portion of the respiratory anatomy that includes the nose, nostrils,

Back 344

hard and soft palates, septum, sinus passages, tongue and jaw.

Front 345

Uvula

Back 345

Uvula: A small soft structure hanging from the soft palate above the back of the

Back 346

tongue.

Front 347

Uvulopalatopharyngoplasty (UPPP)

Back 347

Uvulopalatopharyngoplasty (UPPP): A surgical procedure in which tissues are removed

Back 348

from the upper airway to treat OSA.

Front 349

Ventricles

Back 349

Ventricles: Chambers of the heart that receive blood from the atria and pumps it to the

Back 350

arteries.

Front 351

Ventricular Fibrillation (V‐Fib)

Back 351

Ventricular Fibrillation (V‐Fib): A severe EKG arrhythmia in which the heart is quivering

Back 352

rather than beating, resulting in no discernible waveforms.

Front 353

Ventricular Standstill (Asystole)

Back 353

Ventricular Standstill (Asystole): An EKG arrhythmia in which there is no ventricular

Back 354

activity whatsoever.

Front 355

Ventricular Tachycardia (V‐Tach)

Back 355

Ventricular Tachycardia (V‐Tach): An EKG rhythm characterized by three or more

Back 356

consecutive PVC’s.

Front 357

Vertex sharp transient

Back 357

Vertex sharp transient: Sharp negative potential, maximal at the vertex, occurring

Back 358

spontaneously during sleep or in response to a sensory stimulus during sleep or

Back 359

wakefulness. Amplitude varies but rarely exceeds 250 μv.

Front 360

Volt

Back 360

Volt: A measurement of electrical force.

Front 361

Wakefulness

Back 361

Wakefulness: A state of consciousness characterized by mixed frequency, low voltage

Back 362

EEG waves, eye blinking, eye and muscle movement, and muscle artifact. Also referred

Back 363

to as stage W.

Front 364

Wake Time

Back 364

Wake Time: The total time scored as wakefulness in a Polysomnogram occurring

Back 365

between sleep onset and final wake‐up.

Front 366

Wave

Back 366

Wave: A graphical display of an electrical signal.

Front 367

Wide Complex Tachycardia

Back 367

Wide Complex Tachycardia: Sustained cardiac rhythm of at least 3 consecutive beats

Back 368

with QRS duration ≥120 msec at a rate > 100 beats / minute.

Front 369

Zeitgeber

Back 369

Zeitgeber: German term for an environmental time cue that usually helps entrainment

Back 370

to the 24‐hour day, such as sunlight, noise, social interaction, alarm clock.