Definitions and Abbreviations:
Movement - In diagnostic sleep studies,
abdominal movement is recorded. This is one of the
measures of respiratory effort, reflecting movement
of the diaphragm.
Advanced Sleep Phase Syndrome (ASPS)
- Phases of the daily sleep/wake cycle are advanced
with respect to clock time. This is classified as a
circadian rhythm disorder. The sleep phase occurs
well ahead of the conventional bedtime and the
tendency is to wake up too early.
Alpha rhythm - EEG oscillations,
prominent over the occipital cortex, with a
frequency of 8-13 Hz in adults; indicative of the
awake state; present in most, but not all, normal
individuals; most consistent and predominant during
Alpha intrusion - brief occurrence
of alpha activity during a stage of sleep.
Ambulatory Monitor - Portable
system used to record (continuously) multiple
physiological variables during sleep.
Apnea - Literally means "no
breath"; the cessation of airflow at the nostrils
and mouth for at least 10 seconds.
Apnea index (AI) - A measure of the
severity of sleep apnea; the number of apnea events
Apnea/Hypopnea index (AHI) - the
number of apneas and hypopneas per hour. 5-20=mild,
21-50=moderate, above 51 severe
Arousal - abrupt change from sleep
to wakefulness, or from a "deeper" stage of non-REM
sleep to a "lighter" stage
Arousal Disorder - parasomnia
disorder presumed to be due to an abnormal arousal
function. Classical arousal disorders: sleepwalking,
sleep terrors and confusional arousals.
Arousal Threshold - ease that a
sleeping person is awakened.
Arrhythmia - irregularity or
absence of the heart rhythm caused by disturbances
in transmission of electrical impulses through
Auto Adjusting Continuous Positive Airway
Pressure Device (SmartPAP) (Auto-PAP) - A
type of CPAP machine monitoring changes in breathing
and compensates automatically by making appropriate
adjustments in pressure.
Automatism - automatic
action--especially any action performed apparently
without intention or awareness.
Basic Sleep Cycle - progression
through orderly succession of sleep states and
stages. For the healthy adult, the first cycle is
begins by going from wakefulness to non-REM sleep.
The first REM period follows the first period of
non-REM sleep, and the two sleep states continue to
alternate throughout the night with an average
period of about 90 minutes. A night of normal human
sleep usually consists of 4-6 non-REM/REM sleep
Benzodiazepines - developed in the
1950's, this class of compounds tranquilize and
Beta Activity - brain waves with a
frequency of greater than 13 Hz (Hertz).
Bi-Level - Bi-level pressure device
used to treat sleep apnea. The "bi" refers to two
pressures: a lower pressure for exhalation and a
higher pressure for inhalation. Bi-Level machines
are more expensive than a standard CPAP, but some
patients tolerate it better because they can exhale
comfortably against the constant inhalation
pressure. (Sometimes called Bi-PAP, but that is a
trademark name of one system)
Biological Clock - term for the
brain process causing us to have 24-hour
fluctuations in body temperature, hormone secretion,
and other bodily activities. The most important
function fosters the daily alternation of sleep and
wakefulness. The biological clock is found in a pair
of tiny bilateral brain areas called the
Body Position - four positions are
identified which a patient may be sleeping; back,
left side, right side or abdomen. The time spent
sleeping in each position and the number of
respiratory events in a particular position are
Bradycardia - heart rhythm with a
rate lower than 60 beats per minute in an adult.
Brain Waves - the brain's
spontaneous electrical activity studied by
Bruxism - teeth grinding during
Cardiac Arrest - sudden cessation
of the heart beat.
Cardiovascular - Pertaining to
blood vessels and the heart
Cataplexy - sudden, dramatic
decrement in muscle tone and loss of deep reflexes
that leads to muscle weakness, paralysis, or
postural collapse. Usually caused by outburst of
emotion: laughter, startle, or sudden physical
exercise; one of the tetrad of symptoms of
Central apnea - absence of airflow
and inspiratory effort; apnea caused by irregularity
in the brain's control of breathing. Central
Nervous System (CNS) - brain and spinal
Cheyne-Stokes respiration -
breathing pattern typified by regular
"crescendo-decrescendo" or waxing and waning
fluctuations in respiratory rate and tidal volume.
Chronotherapy - treatment for
circadian rhythm sleep disorder by systemically
changing sleeping and waking times to reset the
Circadian rhythm - innate, daily,
fluctuation of behavioral and physiological
functions, including sleep waking, generally tied to
the 24 hour day-night cycle but sometimes to a
different (e.g., 23 or 25 hour) periodicity when
light/dark and other time cues are removed.
Compliance - adhering to or
conforming with a regimen of treatment such as CPAP
CPAP - Continuous Positive Airway
Pressure; the device used to treat sleep apnea by
sending positive airway pressure at a constant,
continuous pressure to help keep an open airway,
allowing the patient to breathe normally through
his/her nose and airway
- pressure needed to maintain an open airway in a
sleep apnea patient treated with CPAP, expressed in
centimeters of water (cm H20). The positive pressure
can range from 5 - 20 cm H20. Different patients
require different pressures. The value is determined
in a CPAP titration study.
Deep Sleep - refers to combined
non-REM sleep stages 3 and 4 in sleep studies
Delayed sleep phase - A condition
occurring when the clock hour at which sleep
normally occurs is moved back in time in a given, 24
hour sleep-wake cycle. The result is a temporarily
displaced (delayed) occurrence of sleep within the
24 hour cycle.
Delta sleep - stage(s) of sleep in
which EEG delta waves are prevalent or predominant
(sleep stages 3 and 4, respectively).
Delta waves - EEG activity with a
frequency less than 4 Hz. In human sleep stage
scoring, conventionally the minimum criteria for
scoring delta waves is 75 uV (peak-to-peak)
amplitude, and 0.5 second duration (2 Hz).
Diagnostic Sleep Study - monitoring
of several physiological activities in a sleeping
individual. Usually performed to determine the
absence or presence of a specific sleep disorder.
The sleep study can occur in a sleep disorders
center or in a patient's home with portable
Diaphragm - large, concave muscle
attached to the rib cage at bottom of the chest (top
of the abdomen). Inhalation occurs when diaphragm
contracts. Exhalation is passive as the muscle
Diurnal - active and wakeful in the
daytime versus active in the nighttime
DME - Durable Medical Equipment.
Equipment such as wheelchairs and walkers which are
prescribed for use by or on the order of a
physician, also includes CPAP and BI-Level machines.
Drowsiness, Drowsy - quiet
wakefulness occurring prior to sleep onset.
Dyssomnia - a disorder of sleep or
wakefulness; not a parasomnia
Electrocardiography (EKG) - a
method of measuring the electrical activity of the
Electrodes - small devices
transmitting biological electrical activity from
subject to polygraph
Electroencephalogram (EEG) -
recording through the scalp of electrical potentials
from the brain and the changes in these potentials.
The EEG is one of the three basic variables (along
with the EOG & EMG) used to score sleep stages and
waking. Surface electrodes are used to record sleep
in humans, recording potential differences between
brain regions and a neutral reference point, or
between brain regions.
Electromyogram (EMG) - recording of
electrical activity from the muscular system; in
sleep recording, synonymous with resting muscle
activity or potential. The chin EMG, along with EEG
and EOG, is one of the three basic variables used to
score sleep stages and waking. Surface electrodes
are used to record sleep in humans, measuring
activity from the submental or masseter muscles.
These reflect the changes in resting muscle
activity. During REM sleep the chin/cheek EMG is
Electro-oculogram (EOG) - recording
of voltage changes resulting from shifts in position
of the eyeball-possible because each globe is a
positive (anterior) and negative (posterior) dipole;
along with the EEG and the EMG, one of the three
basic variables used to score sleep stages and
waking. Human sleep recordings utilize surface
electrodes placed near the eyes to record the
movement of the eyeballs. Rapid eye movements in
sleep indicate a certain stage of sleep ( usually
ENT - Ear, Nose and Throat. A
doctor specializing in diseases of the Ear, Nose and
Throat. These specialists often do surgery as well,
and may be referred to as an ENT surgeon.
EPAP - Expiratory Positive Airway
Pressure. Pressure prescribed for the expiratory
(breathing out) phase of an individual on Bi-level
CPAP therapy for OSA (obstructive sleep apnea).
Epidemiology - Scientific
discipline studying the incidence, distribution, and
control of disease in a population. Includes the
study of factors affecting the progress of an
illness, and, in the case of many chronic diseases,
their natural history.
- A standard 30 second duration of the sleep
recording that is assigned a sleep stage
designation; for special purposes, occasionally
longer or shorter epochs are scored.
Epworth Sleepiness Scale - index of
sleep propensity during the day as perceived by
patients, and derived from the answers to 8
Esophageal Pressure - measurement
used to determine respiratory effort and by
inference, airway resistance. Considered an invasive
measure, generally used only in polysomnographic
testing, conducted in sleep disorders centers.
Excessive daytime sleepiness or somnolence
(EDS) - subjective report of difficulty in
staying awake, accompanied by a ready entrance into
sleep when the individual is sedentary
Expiratory Phase - air is expelled
during this phase of the breathing cycle
Fatigue - feeling of tiredness or
weariness usually associated with performance
Fiberoptic Nasopharyngoscope -
flexible fiberoptic scope used in the examination of
nasal passages, pharynx, hypopharynx and larynx.
Fibromyalgia - a disease syndrome whose primary
symptoms are muscle pain and fatigue.
Flattening Index - number
indicating the amount of airflow limitation caused
by partial closure of the upper airway. 0.3
indicates an open airway, 0.15 is mildly obstructed,
0.1 is severely limited airflow, and 0.0 reflects a
totally closed airway. Flattening Index is used to
identify the condition known as Upper Airway
Resistance Syndrome (UARS), and is continuously
recorded in both diagnostic sleep studies and CPAP
Flow Limitation - the partial
closure of the upper airway impeding the flow of air
into the lungs.
Forbidden Zone - the period of
strongest clock-dependent alerting, usually in the
evening. Prevents falling asleep.
Fragmentation (pertaining to Sleep
Architecture) - interruption of a sleep
stage as a result of the appearance of a lighter
stage, or to the occurrence of wakefulness, which
leads to disrupted non-REM-REM sleep cycles.
GABA (Gamma-Amniobutyric Acid) -
major neurotransmitter in the brain, which is
considered to be involved in muscle relaxation,
sleep, diminished emotional reaction and sedation.
Gastroesphageal Reflux Disease (GERD)
- flow of stomach acid upwards into the esophagus
that can cause arousals and disrupt sleep.
Genioglossus tongue advancement - a
possible surgical treatment used for sleep apnea
and/or snoring, improving the airway behind the base
of the tongue. The genioglossus, the main tongue
muscle, relaxes during sleep, often allowing the
tongue to fall into the airway. The muscle attaches
to the middle of the lower jaw. A segment of bone
containing this muscle is pulled forward and
stabilized, opening the airway space behind the
Habitual Snorers - those who snore
nearly every night
Heart Rate or beats per minute (bpm)
- pace/speed of the heart measured in beats per
minute. 60-80 is considered normal in adults.
Hertz (Hz) - unit of frequency;
equal to cycles per second (cps).
Histogram (sleep) - graph
indicating sleep stages though out the night.
Humidification - moisture is added
to the airflow as an adjunct to CPAP (Continuous
Positive Airway Pressure) therapy in treating
obstructive sleep apnea (OSA). Humidification can be
added to the CPAP by diverting the airflow over or
through a cool or heated water reservoir
(humidifier) to prevent the upper airway from drying
Hyoid Suspension - a possible
surgical procedure sometimes used in the treatment
of sleep apnea and/or snoring, designed to improve
the airway behind the base of the tongue. The hyoid
bone is located in the neck where some tongue
muscles attach. The hyoid bone is pulled forward in
front of the voice box and can open the airway space
behind the tongue.
Hyperactivity - typical behavior in
a child with a sleep disorder which is causing lack
of quality sleep
Hypercapnia - excessive or elevated
carbon dioxide in the blood
Hyperirritability - Extreme
irritability; seen in sleep deprived subjects.
Hypersomnia - excessive, prolonged
Hypertension - High blood pressure.
Hypnagogic imagery (hallucinations)
- Vivid sensory images occurring at sleep onset but
particularly vivid with sleep-onset REM periods;
feature of narcoleptic REM naps.
Hypnagogic startle - "sleep start"
or sudden body jerk, observed normally just at sleep
onset, resulting in at least momentary awakening
Hypnophobia - Morbid fear of
Hypnotics - Sleep-inducing drugs.
Hypopharynx - lowermost portion of
the pharynx leading to the larynx and esophagus.
Hypopnea - shallow breathing in
which the air flow in and out of the airway is less
than half of normal--usually associated with oxygen
Hypoventilation - reduced rate and
depth of breathing.
Hypoxemia - abnormal lack of oxygen
in the blood in the arteries.
Hypoxia - deficiency of oxygen
reaching the tissues of the body.
Imidazopyridines - New class of
compounds inducing sleepiness. (Zolpidem, trade name
Ambien, is in this class).
Inappropriate Sleep Episodes -
unplanned sleep periods often occuring in an unsafe
situation (i.e., while driving). These episodes are
always due to sleep deprivation.
Insomnia - complaint describing
difficulty in sleeping
Inspiratory Phase - part of the
breathing cycle in which air is inhaled.
Invasive - referring to a medical
procedure in which a bodily orifice or the skin must
be penetrated for the purpose of collecting data, or
for diagnosing or treating a disorder
IPAP - Inspiratory Positive Airway
Pressure. Physician prescribed pressure for the
inspiratory phase on a Bi-level CPAP device, used in
the treatment of OSA.
Jet Lag - disturbance induced by a
major rapid shift in environmental time during
travel to a new time zone
K-Alpha - type of microarousal; K
complex followed by several seconds of alpha rhythm.
K complex - sharp, negative,
high-voltage EEG wave, followed by a slower,
positive component. K complex, occurring
spontaneously during NREM sleep, beginning in (and
defining) stage 2. K complexes can be elicited
during sleep by external (particularly auditory)
stimuli as well.
Laser assisted uvulopalatoplasty (LAUP)
- can eliminate or decrease snoring but has not been
shown to be effective in the treatment of sleep
Leg Movement - Leg movements are
recorded in both diagnostic sleep studies and
Letter of Medical Necessity (LMN) -
certification by a physician that the prescribed
item(s) is/are medically indicated, reasonable and
necessary with reference to the standards of medical
practice and treatment of a patient's condition
Light-Dark Cycle - periodic pattern
of light (artificial or natural) alternating with
Light Sleep - term used to describe
non-REM sleep stage 1, and sometimes, stage 2.
Light Therapy - used in the
treatment of SAD (Seasonal Affective Disorder) and
other conditions. Exposes the eyes to light of
appropriate intensity and duration and at the
appropriate time of day to effect the timing,
duration and quality of sleep.
Limit-Setting Sleep Disorder -
disorder due to child's difficulty in falling asleep
by delaying and refusing to go to bed
Linear Sleepiness Rating Scale -
measure of subjective sleepiness. The scale contains
a horizontal line, 100 mm in length--the right
extreme is labeled "Very Sleepy" and the left
extreme is labeled "Very Wide Awake."
Macroglossia - large tongue;
usually a congenital disorder (present at birth)
Maxillofacial - pertaining to the
jaws and face.
Mandibular Maxillary Osteotomy and
Advancement (MMOA) - procedure developed
for patients with retrolingual obstruction, patients
with retropalatal and retrolingual obstruction who
have not responded to CPAP and
Melatonin - hormone secreted by the
brain's pineal gland
Micro-arousal - partial awakening
Micro-sleep - period lasting up to
a few seconds during which the polysomnogram
suddenly shifts from waking characteristics to
Mixed (sleep) apnea - interruption
in breathing during sleep beginning as a central
apnea then becoming an obstructive apnea.
Monocyclic - a single major sleep
period and a single major wake period in a 24-hour
Motor Activity in Sleep - any
muscular movement during sleep
Motor Atonia - the absence of
muscle activity during sleep
Movement arousal - body movement
associated with arousal or awakening; a sleep
Movement time - term used in sleep
record scoring to denote when EEG and EOG tracings
are obscured for more than 15 seconds due to
Multiple sleep latency test (MSLT)
- a series "nap tests" utilized in the assessment of
excessive daytime sleepiness.
Muscle Tone - amount of tension in
Myoclonus - muscle contractions in
the form of "jerks" or twitches.
Nap - short period of planned sleep
generally obtained at a time separate from the major
Narcolepsy - sleep disorder
characterized by excessive sleepiness, cataplexy,
sleep paralysis, hypnogogic hallucinations, and an
abnormal tendency to pass directly from wakefulness
into REM sleep
Nasal Airflow/Nasal Ventilation -
recording of the complete respiratory cycle by
measuring inspiratory and expiratory airflow
National Commission on Sleep Disorders
Research (NCSDR) - the commission (created
by the U.S. Congress in 1990) conducted a
comprehensive study of the social and economic
impact of sleep disorders in America and made
recommendations based on its findings to the
Congress in January 1993
Neurology - branch of medicine that
referring to the nervous system and its diseases
Neurotransmitters - endogenuous
chemical components that are released from axon
terminals of one neuron and transmit the signal to
the next neuron by combining with its receptor
molecules. Neurotransmitters important in the
control of sleep and wakefulness include:
norepinephrine, serotonin, acetylcholine, dopamine,
adrenaline and histamine.
Nightmare - unpleasant and/or
frightening dream occurring in REM sleep (different
from a night terror)
Night Terrors - also known as sleep
terrors, or pavor nocturnus. Night terrors are
characterized by an incomplete arousal from slow
wave sleep. If, the individual is awakened during a
night terror, he/she is usually confused and does
not remember details of the event. Night terrors are
different from nightmares; if an individual is
awakened during a nightmare, he/she functions well
and may have some recall of the nightmare.
Nocturia - excessive, often
frequent, urination during the night
Nocturnal - "Of the night;"
pertaining to events happening during sleep or the
hours of darkness.
Nocturnal Confusion - episodes of
delirium and/or disorientation near or during
nighttime sleep; often seen in victims of Alzheimers
Disease and more common in the elderly
Nocturnal sleep - related eating
disorder (NS-RED)- Getting up during the night and
eating while sleepwalking. No recall in the morning.
Nocturnal Enuresis (Bedwetting) -
urinating while asleep
Non-Invasive - Medical procedure
not penetrating the skin or a body cavity.
NREM or non-REM sleep -
characterized by slower and larger brain waves and
little or no dream behavior; quiet sleep, slow-wave
sleep; approximately 80% of sleep
NREM Sleep Intrusion - brief period
of NREM sleep patterns appearing in REM sleep; a
portion of NREM sleep not appearing in its usual
sleep cycle position
Obesity-Hypoventilation Syndrome -
term applied to obese individuals hypoventilating
Obstructive apnea - cessation of
airflow (at least 10 seconds) in the presence of
continued inspiratory effort; cessation of breathing
during sleep, due to a mechanical obstruction, such
as a semi-collapsed trachea, tongue relaxed to back
of the throat, or a large among of tissue in the
Obstructive Hypopnea - periodic and
partial closure of the throat during sleep resulting
in reduced air exchange at the level of the mouth
Ondine's Curse - the respiratory
center in the brain is unable to stimulate breathing
in response to an increased amount of carbon dioxide
in the blood. Ondine's Curse or central alveolar
hypoventilation typically worsens during sleep.
Optimum Sleep - average amount of
sleep needed every night by an individual.
Oxygen Desaturation - less than
normal amount of oxygen carried by hemoglobin in the
blood; values below 90% are considered abnormal
Oxygen Saturation - measure of
oxygen carried by hemoglobin in the blood. Normal
values 90% - 100%.
Oximeter (Pulse) - gives estimates
of arterial oxyhemoglobin saturation (SaO2) by
utilizing selected wavelengths of light to non
invasively determine the saturation of oxyhemoglobin
Oximetry (Pulse) - continuous
monitoring of oxygen saturation of arterial blood
from a pulse oximeter; the sensor is usually
attached to the finger.
O2 - Chemical symbol for oxygen.
Criterion lowest percent O2 saturation: Greater than
85%=mild, 80% to 85%=moderate, less than 80%=severe
Parasomnia - an event happening
during sleep, or induced or exacerbated by sleep,
such as sleepwalking or asthma; not a dyssomnia.
Paroxysmal nocturnal dyspnea (PND)
- respiratory distress and shortness of breath due
to pulmonary edema, appearing suddenly and often
awakening the sleeping individual.
Pathological Sleep - abnormal sleep
Pavor Nocturnus (Night Terrors) -
See Night Terrors.
Perceptual Disengagement - change
in consciousness at the onset of sleep when
environmental stimuli are no longer perceived, and
there is no longer any conscious, meaningful
interaction with the environment.
Periodic Breathing - repetitive
apneic pauses, common in premature infants.
Periodic Limb Movement Disorder -
also known as periodic leg movements and nocturnal
myoclonus. Characterized by periodic episodes of
repetitive and highly stereotyped limb movements
occuring during sleep. The movements are often
associated with a partial arousal or awakening;
however, the patient is usually unaware of the limb
movements or frequent sleep disruption. Between the
episodes, the legs are still. There can be marked
night-to-night variability in the number of
movements or in the existence of movements.
- continuing insomnia responding poorly to
Pharynx - area posterior to the
nares and the oral cavity; passageway for air from
the nasal cavity and/or the mouth to the lungs via
the larynx and the trachea, for food and liquids
from the mouth to the esophagus
Phase advance - movement to a
position earlier in the 24 hour sleep - wake cycle
of a period of sleep or wake; for example, a shift
of the sleep phase from 11 p.m. - 7 a.m. to 8 p.m. -
Phase delay - Phase delay is
exactly the opposite of phase advance, i.e., a shift
later in time.
Phasic (Event/Activity) - brain,
muscle, or autonomic related event of a brief and
episodic nature occurring in sleep. Usually occur
during REM sleep, such as eye movements and/or
Photoperiod - duration of light in
a light/dark cycle.
Pickwickian Syndrome - obesity
accompanied by somnolence, lethargy, chronic
hypoventilation, hypoxia, and secondary polycythemia
(a condition marked by an abnormal increase in the
number of circulating red blood cells); usually has
severe obstructive sleep apnea Pineal Gland
- gland in the brain secreting the hormone
PLMD-Arousal Index - number of
sleep-related periodic leg movements per hour of
sleep that are associated with an EEG arousal
Polycyclic - multiple sleep periods
and wake periods in a 24-hour day.
PO2 - partial pressure of oxygen
(O2) in the blood. A value above 60 is usually
considered a safe level: lower than 60 indicated
hypoxemia and potential danger for the patient.
Polysomnogram (PSG) - continuous
and simultaneous recording of physiological
variables during sleep, i.e., EEG, EOG, EMG (the
three basic stage scoring parameters), EKG,
respiratory air flow, respiratory excursion, lower
limb movement, and other electrophysiological
Polysomnograph - biomedical
instrument for the measurement of multiple
physiological variables of sleep
Polysomnographic Technologist -
health care professional trained in performing
diagnostic sleep studies
Post-Prandial Drowsiness -
sleepiness that occurs after a meal, usually lunch
Post-Traumatic Stress Disorder -
re-experiencing of a traumatic event in the form of
repetitive dreams, recurrent and intrusive daytime
recollections, and/or dissociative flashback
Premature morning awakening - early
termination of the sleep period in a sleep
maintenance DIMS due to inability to return to sleep
after the last of several awakenings
Prescribed CPAP Pressure -
pressure(s) or settings determined by a CPAP
titration sleep study, which a physician prescribes
for a patient's CPAP therapy machine
Pulse Oximetry - non-invasive
measure of oxygen saturation; that is the amount of
oxygen saturated in the hemoglobin in terms of
percentage; not as accurate as the values obtained
from an arterial blood gases (ABG) test and should
only be used as a gauge of oxygenation. Normal
ranges are between 95-100%.
Quiet Sleep - The term frequently
used instead of NREM sleep to describe the sleep of
Radiofrequency (RF) -
Electromagnetic radiation in the frequency range 3
kilohertz (kHz) to 300 gigahertz (GHz); considered
to include microwaves and radio waves. Microwaves
occupy the spectral region between 300 GHz and 300
MHz, while RF or radio waves include 300 MHz to 3
Radiofrequency (RF) Procedure (also known as
Somnoplasty) - procedure for treating nasal
obstruction, snoring and in some cases, sleep apnea.
The procedure uses radiowave energy to reduce
snoring and the size of the soft palate.
RDI - Respiratory Disturbance
Index, includes all respiratory events per hour.
REM sleep, rapid eye movement sleep
- sleep characterized by the active brain waves,
flitting motions of the eyes, and weakness of the
muscles; most dreaming occurs in this stage, which
accounts for about 20% of sleep in adults.
REM Density - A function that
expresses the frequency of eye movements per unit of
time during REM sleep.
REM-Associated Disorders - Sleep
disturbances that occur in REM sleep.
REMS latency - The period of time
in the sleep period from sleep onset to the first
appearance of stage REMS.
REM Motor Atonia - The active
suppression of activity in the antigravity and
voluntary muscles during REM sleep. The muscles are
completely flaccid and limp.
REM onset - designation for
commencement of a REM period; used also as a
shorthand term for a sleep-onset REM period
REM period - REM portion of a
NREM-REM cycle; early in the night it may be as
short as a half-minute, whereas in later cycles
longer than an hour.
REM rebound or recovery -
lengthening and increase in frequency and density of
REM periods, which results in an increase in REM
percent above base line. REM rebound follows REM
deprivation once the inhibitory influence is removed
REM Sleep Behavior Disorder (RBD) -
disorder in which REM motor atonia is partially or
completely absent and the individual acts out the
ongoing dream. The behavior in REM behavior disorder
is often correlates with the ongoing, hallucinatory
REM dream episode.
REM Sleep Episode - REM sleep
portion of a NREM-REM sleep cycle. Early in the
first sleep period, episodes may be only several
minutes in duration. Later REM episodes almost are
always longer, 20 to 30 minutes up to an hour.
REM Sleep Intrusion - brief
interval of REM sleep appearing out of its usual
positioning in the NREM-REM sleep cycle.
REM Sleep Latency - interval from
sleep onset to the first appearance of REM sleep
REM Sleep Onset - designation for
the first epoch of a REM sleep episode
REM Sleep Percent - proportion of
total sleep time occupied by REM sleep
REM Sleep Rebound - compensatory
increase in REM sleep following experimental
reduction. Extension of time in, and an increase in
frequency and density of REM sleep episodes; usually
an increase in REM sleep percent of total sleep time
above baseline values
Respiratory Care Practitioner (RCP)
- licensed health care professional specifically
trained in cardiopulmonary assessment, diagnostics,
therapy administration, and patient education,
including the identification and treatment of sleep
Restless Legs Syndrome (RLS) -
sleep disorder characterized by a deep creeping, or
crawling sensation in the legs that tends to occur
when an individual is not moving. There is an almost
irresistible urge to move the legs; the sensations
are relieved by movement.
Restlessness (Referring to
Quality of Sleep)
- Persistent or recurrent body movements, arousals,
and/or brief awakenings in the course of sleep
Sedatives - compounds tending to
calm, and reduce nervousness or excitement and
Sedentary Situation - not requiring
physical activity, e.g. working at a desk, sitting
in a meeting or in a theater, watching television.
Septoplasty - surgery on the nasal
septum (dividing the nasal passage)
Serotonin - neurotransmitter in the
brain that modulates mood, appetite, sexual
activity, aggression, body temperature and sleep
Shiftwork - working hours outside
of the conventional daytime hours of 9:00 a.m. to
Sleep - a state marked by lessened
consciousness, lessened movement of the skeletal
muscles, and slowed-down metabolism
Sleep Apnea - cessation of
breathing for 10 or more seconds during sleep
Sleep Architecture - NREM/REM stage
and cycle infrastructure of sleep understood from
the vantage point of the quantitative relationship
of these components to each other
Sleep cycle - synonymous with NREM-REM
Sleep Debt - result of recurrent
sleep deprivation which occurs over time when an
individual does not experience a sufficient amount
of the restorative daily sleep that is required to
maintain a sense of feeling rested and refreshed.
Sleep Deprivation - acute or
chronic lack of sufficient sleep.
Sleep Disorders - broad range of
illnesses arising from many causes, including,
dysfunctional sleep mechanisms, abnormalities in
physiological functions during sleep, abnormalities
of the biological clock, and sleep disturbances that
are induced by factors extrinsic to the sleep
Sleep efficiency (SE) - proportion
of sleep in the period potentially filled by
sleep--ratio of total sleep time to time in bed
Sleep Episode - interval of sleep
that may be voluntary or involuntary
Sleep Extension - extending sleep
time by increasing the time in bed
Sleep Fragmentation - brief
arousals occurring throughout the night, reducing
the total amount of time spent in the deeper levels
Sleep hygiene - conditions and
practices that promote continuous and effective
sleep, including regularity of bedtime and arise
time; conforming time spent in bed to the time
necessary for sustained and individually adequate
sleep (i.e., the total sleep time sufficient to
avoid sleepiness when awake); restriction of alcohol
and caffeine beverages in the period prior to
bedtime; employment of exercise, nutrition, and
environmental factors so that they enhance, not
disturb, restful sleep
Sleep Hyperhydrosis - excessive
sweating during sleep.
Sleep Inertia - feelings of
grogginess and/or sleepiness that persist longer
than 10 to 20 minutes after waking up
Sleep interruption - breaks in the
sleep architecture resulting in arousal and
Sleep latency - time period
measured from "lights out," or bedtime, to the
beginning of sleep
Sleep log (diary) - daily, written
record of an individual's sleep-wake pattern
containing such information as time of retiring and
arising, time in bed, estimated total sleep period,
number and duration of sleep interruptions, quality
of sleep, daytime naps, use of medications or
caffeine beverages, nature of waking activities, and
Sleep - maintenance DIMS or
insomnia - disturbance in maintaining sleep once
achieved; persistently interrupted sleep without
difficulty falling asleep
Sleep Mentation - thoughts,
feelings, images, perceptions, hallucinations, and
active dreams taking place during sleep
Sleep onset - transition from wake
to sleep, normally into NREM stage 1 (but in certain
conditions, such as infancy and narcolepsy, into
Sleep Onset Imagery - images and
experiences during the moments following the
transition from wake to sleep
Sleep-onset REM period - atypical
beginning of sleep by entrance directly into stage
Sleep paralysis - waking and not
being able to move for a short period of time,
usually occurs out of REM (dream) sleep.
Sleep pattern (24 hour sleep-wake pattern)
- individual's clock hour schedule of bedtimes and
rise times as well as nap behavior: may also include
time and duration of sleep interruptions
Sleeping Pills - compounds that
have a sedative effect, used to produce sleepiness
Sleep Related Accidents - accidents
caused by individuals who were sleep deprived and
who, as a result, had impaired judgment
Sleep Restriction - limitation of
the number of hours in bed
Sleep spindle - episodically
appearing, spindle-shaped aggregate of 12-14 Hz
waves with a duration of 0.5-1.5 seconds, one of the
identifying EEG phenomena of NREM stage 2 sleep
Sleep Stage Demarcation -
significant polysomnographic characteristics that
distinguish the boundaries of the sleep stages.
Sleep stage NREM - major sleep
state apart from REMS; comprises sleep stages 1-4
Sleep stage 1 - a stage of NREM
sleep occurring after wake. Its criteria consist of
a low-voltage EEG with slowing to theta frequencies,
alpha activity less than 50%, EEG vertex spikes, and
slow rolling eye movements; no sleep spindles,
K-complexes, or REMS. Stage 1 normally assumes 4-5%
of total sleep.
Sleep stage 2 - a stage of NREM
sleep characterized by sleep spindles and K
complexes against a relatively low-voltage,
mixed-frequency EEG background; high-voltage delta
waves may comprise up to 20% of stage 2 epochs;
usually accounts for 45-55% of total sleep time.
Sleep stage 3 - a stage of NREM
sleep defined by at least 20 and not more than 50%
of the period (30 second epoch) consisting of EEG
waves less than 2 Hz and more than 75 uV (high
-amplitude delta waves); a "delta" sleep stage; with
stage 4, it constitutes "deep "NREM sleep; appears
usually only in the first third of the sleep period;
usually comprises 4-6% of total sleep time.
Sleep stage 4 - all statements
concerning NREM stage 3 apply to stage 4 except that
high-voltage, slow EEG waves, cover 50% or more of
the record; NREM stage 4 usually takes up 12-15% of
total sleep time. Somnambulism, sleep terror, and
sleep-related enuresis episodes generally start in
stage 4 or during arousals from this stage
Sleep stage REM - the stage of
sleep found in all mammal studies, including man, in
which brain activity is extensive, brain metabolism
is increased, and vivid hallucinatory imagery, or
dreaming occurs (in humans). Also called
"paradoxical sleep" because, in the face of this
intense excitation of the CNS and presence of
spontaneous rapid eye movements, resting muscle
activity is suppressed. The EEG is a low-voltage,
fast-frequency, non alpha record. Stage REMS is
usually 20-25% of total sleep time.
Sleep structure - similar to sleep
architecture. Sleep structure, in addition to
encompassing sleep stage and cycle relationships,
assesses the within-stage qualities of the EEG and
other physiological attributes.
Sleepiness (somnolence, drowsiness)
- difficulty in maintaining the wakeful state so
that the individual falls asleep if not actively
kept aroused; not simply a feeling of physical
tiredness or listlessness
Sleep talking - talking in sleep
takes place during stage REMS, representing a motor
breakthrough of dream speech, or in the course of
transitory arousals from NREMS and other stages.
Full consciousness is not achieved and no memory of
the event remains. Sleepwalker or Sleepwalking -
individual subject to somnambulism (one who walks
while sleeping). Sleepwalking typically occurs in
the first third of the night during deep NREM sleep
(stages 3 and 4).
Sleep-wake, 24 hour cycle - the
clock hour relationships of the major sleep and wake
phases in the 24 hour cycle: similar to sleep
Sleep-wake shift (change, -reversal)
- sleep wholly or partially moved to a time of
customary waking activity, and the latter is moved
to the habitual sleep period; common in jet lag and
Sleep-Wake Transition Disorder -
disorder occuring during the transition from
wakefulness to sleep or from one sleep stage to
another; a form of parasomnia
Slow wave sleep (SWS) - sleep
stages 3 and 4
SmartPAP (Smart CPAP) - (Smart
[Continuous] Positive Airway Pressure) Medical
device used in the treatment of obstructive sleep
apnea providing preset levels of continuous airflow,
and automatically adjusting to keep the breathing
passages open by sensing changes in airway
integrity. The air flows from the device through a
tube that connects to a nose or face mask.
Snoring - noise produced primarily
with inspiratory respiration during sleep owing to
vibration of the soft palate and the pillars of the
oropharyngeal inlet. Many snorers have incomplete
obstruction of the upper airway, and may develop
obstructive sleep apnea.
- membranous and muscular fold
suspended from the posterior margin of the hard
palate and partially separating the oral cavity from
Somatic Complaints - awareness of
pain or problems in the body
Somnambulism - walking while asleep
Somnifacient - inducing sleep;
hypnotic, as in a drug
Somnolence - prolonged drowsiness
Somnoplasty - commercial name for
radiofrequency treatment of certain sleep disorders
Soporific - causing or tending to
Spindle REMS - condition in which
sleep spindles persist atypically in REMS; seen in
chronic DIMS conditions
Stanford Sleepiness Scale (SSS) -
7-point rating scale consisting of seven numbered
statements describing subjective levels of
Subjective Sleepiness - feelings of
Substance Abuse - excessive use of
alcohol or drug; substances can cause sleep
Subwakefulness syndrome - syndrome
defined as a defect in the CNS support system for
waking. The few individuals reported with
subwakefulness syndrome have daytime drowsiness and
daytime sleep episodes that are always composed of
NREMS stages 1 or 2. The naps occur repetitively
Sudden Infant Death Syndrome (SIDS)
- sudden and unexpected death of an apparently
healthy infant, whose death remains unexplained
after the performance of an adequate postmortem
investigation. Death usually occurs during sleep.
SIDS is a classification that is used to describe a
deceased infant. It is not a disease, nor can it be
a diagnosis for a living baby.
Synchronization - chronobiological
term used to indicate that two or more rhythms recur
with the same phase relationship. In an EEG tracing,
the term is used to indicate an increased amplitude
with an occasional decreased frequency of the
Synchrony - scheduling sleep to
synchronize with the biological clock
Tachycardia - rapid heart rate,
usually defined by a pulse rate of over 100 beats
per minute (bpm).
Thermocouples - small devices
placed near the nostrils or mouth to measure air
flow by sensing temperature changes; expired air is
warmer than inspired air.
Thermoregulation - regulation of
body temperature in mammals.
Theta waves - EEG activity with a
frequency of 4-8 Hz
Thoracic Excursion - thoracic
(chest) movement, indicating respiratory effort.
Usually measured by the placement of a sensor band,
which includes a strain gauge around the chest. The
sensor band records chest wall movement associated
Tidal Volume - amount of air that
passes in and out of the lungs in an ordinary
breath; usually expressed in liters
Titration - progressive, stepwise
increase in CPAP pressure applied during a
polysomnogram to establish the optimal treatment
Tolerance - in pharmacology, refers
to the reduced responsiveness to a drug's action as
the result of previous continued and/or multiple
Tonic (Event/Activity) - brain,
muscle, or autonomic events, which are continuous.
Usually refers to continuous activity (e.g. muscle
atonia) during REM sleep.
Tonsils - pair of prominent masses
of lymphoid tissue that are located opposite each
other in the throat between the anterior and
posterior pillars of the fauces (the narrow passage
from the mouth to the pharynx situated between the
soft palate and the base of the tongue). Composed of
lymph follicles grouped around one or more deep
Tonsillectomy - surgical removal of
Total Recording Time - duration of
time from sleep onset to final awakening. I n
addition to total sleep time, it is comprised of the
time taken up by wake periods and movement time
Total sleep period - period of time
measured from sleep onset to final awakening. In
addition to total sleep time, it is comprised of the
time taken up by arousals and movement time until
Total sleep time (TST) - amount of
actual sleep time in a sleep period; equal to total
sleep period less movement and awake time. Total
sleep time is the total of all REMS and NREMS in a
Tracheotomy - surgical procedure to
create an opening in the trachea (windpipe) so that
one can breathe
Tracheostomy - refers to the
opening in the trachea. As a treatment for severe
obstructive sleep apnea, a tube to assist
oxygenation and ventilation and/or to overcome an
obstruction in the airway located superiorly.
Transducer - device designed to
convert energy from one form to another
Transient Arousals - brief
awakenings from sleep
Transient Insomnia - difficulty
sleeping for only a few nights
Tricyclic Antidepressants -
medication for depression. Most tricyclic
antidepressants also reduce REM sleep; also used to
control cataplectic attacks, hypnogogic
hallucinations, and sleep paralysis.
Tumescence (penile) - hardening and
expansion of the penis: penile erection. Commonly
referred to as nocturnal penile tumescence (NPT) in
Turbinate - small, shelf-like,
cartilaginous structures covered by mucous
membranes, which protrude into the nasal airway to
help warm, humidify, and cleanse inhaled air on its
way to the lungs.
Twilight Zone - slang popular term
to describe the waking state of individuals whose
MSLT scores are 5 minutes or less. Such individuals
are usually sleep deprived or suffer from a sleep
Twitch (Body Twitch) - very small
body movement such as a local foot or finger jerk
which is not usually associated with an arousal.
Unattended CPAP Titration Study -
sleep study that is usually performed in the home,
after determining that a patient has a sleep related
breathing disorder such as OSA or Upper Airway
Resistance Syndrome, and is likely to benefit from
Unintended Sleep Episode - sleep
episode that is not planned and may happen during an
activity in which such an episode is hazardous, such
as when driving a car or working with machinery
Upper Airway - part of the
respiratory anatomy that includes the nose,
nostrils, sinus passages, septum, turbinates; the
tongue, jaws, hard and soft palate, muscles of the
tongue and throat, etc.
Upper Airway Resistance Syndrome (UARS)
- part of the spectrum of obstructive sleep-related
breathing disorders in which repetitive increases in
resistance to airflow in the upper airway lead to
brief arousals and daytime fatigue. Apneas and
hypopneas (see RDI) may be totally absent. Blood
oxygen levels can be in the normal range.
Uvula - small soft structure
hanging from the bottom of the soft palate in the
midline above the back of the tongue.
Uvulopalatopharyngoplasty (UPPP) -
also abbreviated as UPP or UP3 this operation is
performed on the throat to treat snoring and sleep
apnea. UPPP is an accepted means of surgical
treatment has a curative rate of less than 50%.
Scientific evidence suggests that UPPP works best in
retropalatal and combination retropalatal and
Wake time - total time that is
scored awake in a polysomnogram occurring between
sleep onset and final wake-up
White Noise - mixture of sound
waves extending over a wide frequency range that may
be used to mask unwanted noise that may interfere
Wilkinson Addition Test -
performance test; numbers added for one hour. Often
included in a battery of tests to measure the impact
of acute or chronic sleep loss.
Withdrawal - effects experienced
when a patient stops taking sleeping pills
Zeitgeber - environmental time cue
that entrains biological rhythms to a specific
periodicity. Known Zeitgebers are light, melatonin
and physical activity. To be effective, these
signals must occur when the biological clock is in a
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