Sleep Terms Definitions

Melatonin

hormone secreted by the brain's pineal gland

Epworth Sleepiness Scale

index of sleep propensity during the day as perceived by patients, and derived from the answers to 8 questions.

Macroglossia

large tongue; usually a congenital disorder (present at birth)

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 out.

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 relaxed wakefulness

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).

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 process

Laser assisted uvulopalatoplasty (LAUP)

can eliminate or decrease snoring but has not been shown to be effective in the treatment of sleep apnea.

Soporific

causing or tending to cause sleep

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

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 uvula area.

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.

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

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 dominant activities.

Somnoplasty

commercial name for radiofrequency treatment of certain sleep disorders

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

Insomnia

complaint describing difficulty in sleeping

Sedatives

compounds tending to calm, and reduce nervousness or excitement and foster sleep

Sleeping Pills

compounds that have a sedative effect, used to produce sleepiness

Spindle REMS

condition in which sleep spindles persist atypically in REMS; seen in chronic DIMS conditions

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

Persistent Insomnia

continuing insomnia responding poorly to treatment

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 variables.

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 other data

Hypoxia

deficiency of oxygen reaching the tissues of the body.

REM onset

designation for commencement of a REM period; used also as a shorthand term for a sleep-onset REM period

REM Sleep Onset

designation for the first epoch of a REM sleep episode

Benzodiazepines

developed in the 1950's, this class of compounds tranquilize and sedates

Transient Insomnia

difficulty sleeping for only a few nights

Limit-Setting Sleep Disorder

disorder due to child's difficulty in falling asleep by delaying and refusing to go to bed

Sleep-Wake Transition Disorder

disorder occuring during the transition from wakefulness to sleep or from one sleep stage to another; a form of parasomnia

Sleep-maintenance DIMS or insomnia

disturbance in maintaining sleep once achieved; persistently interrupted sleep without difficulty falling asleep

Jet Lag

disturbance induced by a major rapid shift in environmental time during travel to a new time zone

Photoperiod

duration of light in a light/dark cycle.

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 until wake-up.

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

Arousal Threshold

ease that a sleeping person is awakened

Neurology

branch of medicine that referring to the nervous system and its diseases

Transient Arousals

brief awakenings from sleep

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 responsive phase.

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

Fiberoptic Nasopharyngoscope

flexible fiberoptic scope used in the examination of nasal passages, pharynx, hypopharynx and larynx.

Gastroesphageal Reflux Disease (GERD)

flow of stomach acid upwards into the esophagus that can cause arousals and disrupt sleep.

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 tabulated.

Oximeter (Pulse)

gives estimates of arterial oxyhemoglobin saturation (SaO2) by utilizing selected wavelengths of light to non invasively determine the saturation of oxyhemoglobin (SpO2)

Pineal Gland

gland in the brain secreting the hormone melatonin.

Histogram (sleep)

graph indicating sleep stages thoughout the night

Tumescence (penile)

hardening and expansion of the penis: penile erection. Commonly referred to as nocturnal penile tumescence (NPT) in sleep recordings.

Polysomnographic Technologist

health care professional trained in performing diagnostic sleep studies

Bradycardia

heart rhythm with a rate lower than 60 beats per minute in an adult

Sleep Onset Imagery

images and experiences during the moments following the transition from wake to sleep

Tolerance

in pharmacology, refers to the reduced responsiveness to a drug's action as the result of previous continued and/or multiple exposure

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).

Somnifacient

inducing sleep; hypnotic, as in a drug

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.

Mixed (sleep) apnea

interruption in breathing during sleep beginning as a central apnea then becoming an obstructive apnea

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

REM Sleep Latency

interval from sleep onset to the first appearance of REM sleep

Sleep Episode

interval of sleep that may be voluntary or involuntary

Arrhythmia

irregularity or absence of the heart rhythm caused by disturbances in transmission of electrical impulses through cardiac tissue.

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 relaxes.

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

Oxygen Desaturation

less than normal amount of oxygen carried by hemoglobin in the blood; values below 90% are considered abnormal

Sleep Restriction

limitation of the number of hours in bed

Hypopharynx

lowermost portion of the pharynx leading to the larynx and esophagus

Sleep stage NREM

major sleep state apart from REMS; comprises sleep stages 1-4

Oxygen Saturation

measure of oxygen carried by hemoglobin in the blood. Normal values 90% - 100%.

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."

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.

Tricyclic Antidepressants

medication for depression. Most tricyclic antidepressants also reduce REM sleep; also used to control cataplectic attacks, hypnogogic hallucinations, and sleep paralysis.

Soft Palate

membranous and muscular fold suspended from the posterior margin of the hard palate and partially separating the oral cavity from the pharynx

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 recording equipment.

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. - 4 a.m.

Polycyclic

multiple sleep periods and wake periods in a 24-hour day

Myoclonus

muscle contractions in the form of "jerks" or twitches.

Serotonin

neurotransmitter in the brain that modulates mood, appetite, sexual activity, aggression, body temperature and sleep

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.

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%.

Sedentary Situation

not requiring physical activity, e.g. working at a desk, sitting in a meeting or in a theater, watching television.

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 titrations.

PLMD-Arousal Index

number of sleep-related periodic leg movements per hour of sleep that are associated with an EEG arousal

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.

Tachycardia

rapid heart rate, usually defined by a pulse rate of over 100 beats per minute (bpm).

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 episodes.

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

Apnea/Hypopnea index (AHI)

the number of apneas and hypopneas per hour. 5-20=mild, 21-50=moderate, above 51 severe

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

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.

Theta waves

EEG activity with a frequency of 4-8 Hz

REM Motor Atonia

The active suppression of activity in the antigravity and voluntary muscles during REM sleep. The muscles are completely flaccid and limp.

Diurnal

active and wakeful in the daytime versus active in the nighttime

Compliance

adhering to or conforming with a regimen of treatment such as CPAP

Expiratory Phase

air is expelled during this phase of the breathing cycle

Muscle Tone

amount of tension in a muscle.

Hypercapnia

excessive or elevated carbon dioxide in the blood

Sleep Hyperhydrosis

excessive sweating during sleep.

Nocturia

excessive, often frequent, urination during the night

Hypersomnia

excessive, prolonged sleep

Sleep Extension

extending sleep time by increasing the time in bed

Fatigue

feeling of tiredness or weariness usually associated with performance decrements

Sleep Inertia

feelings of grogginess and/or sleepiness that persist longer than 10 to 20 minutes after waking up

Post-Prandial Drowsiness

sleepiness that occurs after a meal, usually lunch

Thermocouples

small devices placed near the nostrils or mouth to measure air flow by sensing temperature changes; expired air is warmer than inspired air.

Electrodes

small devices transmitting biological electrical activity from subject to polygraph

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.

Delta sleep

stage(s) of sleep in which EEG delta waves are prevalent or predominant (sleep stages 3 and 4, respectively).

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

Cardiac Arrest

sudden cessation of the heart beat.

Tonsillectomy

surgical removal of the tonsils

Sleep cycle

synonymous with NREM-REM cycle

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.

Bruxism

teeth grinding during sleep

Obesity-Hypoventilation Syndrome

term applied to obese individuals hypoventilating during wakefulness.

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 suprachiasmatic nuclei.

Movement time

term used in sleep record scoring to denote when EEG and EOG tracings are obscured for more than 15 seconds due to movement.

Motor Atonia

the absence of muscle activity during sleep

Brain Waves

the brain's spontaneous electrical activity studied by electroencephalography (EEG).

Sleep-wake, 24 hour cycle

the clock hour relationships of the major sleep and wake phases in the 24 hour cycle: similar to sleep pattern.

Electrocardiography (EKG)

a method of measuring the electrical activity of the heart

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.

REM Density

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

Apnea index (AI)

A measure of the severity of sleep apnea; the number of apnea events per hour.

Epoch

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.

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.

Hypnagogic startle

"sleep start" or sudden body jerk, observed normally just at sleep onset, resulting in at least momentary awakening

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

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.

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.

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

Drowsiness

Drowsy - quiet wakefulness occurring prior to sleep onset.

Pavor Nocturnus (Night Terrors)

- See Night Terrors.

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 interruption

- breaks in the sleep architecture resulting in arousal and wakefulness

Transducer

- device designed to convert energy from one form to another

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

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 disorders

GABA (Gamma-Amniobutyric Acid)

- major neurotransmitter in the brain, which is considered to be involved in muscle relaxation, sleep, diminished emotional reaction and sedation.

White Noise

- mixture of sound waves extending over a wide frequency range that may be used to mask unwanted noise that may interfere with sleep

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 wake-up

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 uvulopalatopharyngoplasty (UPPP).

Deep Sleep

- refers to combined non-REM sleep stages 3 and 4 in sleep studies

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.

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 disorder.

Sleep onset

- transition from wake to sleep, normally into NREM stage 1 (but in certain conditions, such as infancy and narcolepsy, into stage REMS)

Stanford Sleepiness Scale (SSS)

7-point rating scale consisting of seven numbered statements describing subjective levels of sleepiness/alertness

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)

O2 -

Chemical symbol for oxygen. Criterion lowest percent O2 saturation: Greater than 85%=mild, 80% to 85%=moderate, less than 80%=severe

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-trough) amplitude, and 0.5 second duration (2 Hz).

Nocturnal sleep-related eating disorder (NS-RED)-

Getting up during the night and eating while sleepwalking. No recall in the morning.

Hypertension

High blood pressure

Abdominal Movement

In diagnostic sleep studies, abdominal movement is recorded. This is one of the measures of respiratory effort, reflecting movement of the diaphragm.

IPAP

Inspiratory Positive Airway Pressure. Physician prescribed pressure for the inspiratory phase on a Bi-level CPAP device, used in the treatment of OSA.

Leg Movement

Leg movements are recorded in both diagnostic sleep studies and titration studies.

Apnea

Literally means "no breath", the cessation of airflow at the nostrils and mouth for at least 10 seconds

Non-Invasive

Medical procedure not penetrating the skin or a body cavity.

Hypnophobia

Morbid fear of falling asleep

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

Imidazopyridines

New class of compounds inducing sleepiness. (Zolpidem, trade name Ambien, is in this class).

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.

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

Restlessness (Referring to Quality of Sleep)

Persistent or recurrent body movements, arousals, and/or brief awakenings in the course of sleep

Cardiovascular

Pertaining to blood vessels and the heart

Phase delay

Phase delay is exactly the opposite of phase advance, i.e., a shift later in time.

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.

Ambulatory Monitor

Portable system used to record (continuously) multiple physiological variables during sleep.

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.

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 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.

RDI

Respiratory Disturbance Index, includes all respiratory events per hour.

REM Sleep Intrusion

brief interval of REM sleep appearing out of its usual positioning in the NREM-REM sleep cycle

Alpha intrusion

brief occurrence of alpha activity during a stage of sleep.

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.

REM-Associated Disorders

Sleep disturbances that occur in REM sleep.

Hypnotics

Sleep-inducing drugs

REMS latency

The period of time in the sleep period from sleep onset to the first appearance of stage REMS.

Quiet Sleep

The term frequently used instead of NREM sleep to describe the sleep of infants.

Hypnagogic imagery (-hallucinations)

Vivid sensory images occurring at sleep onset but particularly vivid with sleep-onset REM periods; feature of narcoleptic REM naps.

Fibromyalgia

a disease syndrome whose primary symptoms are muscle pain and fatigue.

Dyssomnia

a disorder of sleep or wakefulness; not a parasomnia

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 tongue.

Multiple sleep latency test (MSLT)

a series "nap tests" utilized in the assessment of excessive daytime sleepiness.

Monocyclic

a single major sleep period and a single major wake period in a 24-hour day.

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 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

a state marked by lessened consciousness, lessened movement of the skeletal muscles, and slowed-down metabolism

Hypoxemia

abnormal lack of oxygen in the blood in the arteries

Pathological Sleep

abnormal sleep patterns

Arousal

abrupt change from sleep to wakefulness, or from a "deeper" stage of non-REM sleep to a "lighter" stage

Central apnea

absence of airflow and inspiratory effort; apnea caused by irregularity in the brain's control of breathing.

Sleep Related Accidents

accidents caused by individuals who were sleep deprived and who, as a result, had impaired judgment

Sleep Deprivation

acute or chronic lack of sufficient sleep.

Upper Airway Resistance Syndrome (UARS)

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 retrolingual obstruction

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.

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.

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 sleep period.

Tidal Volume

amount of air that passes in and out of the lungs in an ordinary breath; usually expressed in liters

Parasomnia

an event happening during sleep, or induced or exacerbated by sleep, such as sleepwalking or asthma; not a dyssomnia.

Motor Activity in Sleep

any muscular movement during sleep

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

Sleep-onset REM period

atypical beginning of sleep by entrance directly into stage REM

Automatism

automatic action - especially any action performed apparently without intention or awareness

Optimum Sleep

average amount of sleep needed every night by an individual

Somatic Complaints

awareness of pain or problems in the body

Polysomnograph

biomedical instrument for the measurement of multiple physiological variables of sleep

Movement arousal

body movement associated with arousal or awakening; a sleep scoring variable

Central Nervous System (CNS)

brain and spinal cord.

Beta Activity

brain waves with a frequency of greater than 13 Hz (Hertz).

Tonic (Event/Activity)

brain, muscle, or autonomic events, which are continuous. Usually refers to continuous activity (e.g. muscle atonia) during REM sleep.

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 muscle twitches

Cheyne-Stokes respiration

breathing pattern typified by regular "crescendo-decrescendo" or waxing and waning fluctuations in respiratory rate and tidal volume.

Sleep Fragmentation

brief arousals occurring throughout the night, reducing the total amount of time spent in the deeper levels of sleep.

Sleep efficiency (SE)

proportion of sleep in the period potentially filled by sleep--ratio of total sleep time to time in bed

REM Sleep Percent

proportion of total sleep time occupied by REM sleep

CPAP Pressure

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.

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

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 cycles.

Titration

progressive, stepwise increase in CPAP pressure applied during a polysomnogram to establish the optimal treatment pressure

Somnolence

prolonged drowsiness or sleepiness

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

Heart Rate or beats per minute (bpm)

pace/speed of the heart measured in beats per minute. 60-80 is considered normal in adults.

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 crypts.

Arousal Disorder

parasomnia disorder presumed to be due to an abnormal arousal function. Classical arousal disorders: sleepwalking, sleep terrors and confusional arousals.

Inspiratory Phase

part of the breathing cycle in which air is inhaled.

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.

Micro-arousal

partial awakening from sleep

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.

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.

Obstructive Hypopnea

periodic and partial closure of the throat during sleep resulting in reduced air exchange at the level of the mouth and/or nostril.

Light-Dark Cycle

periodic pattern of light (artificial or natural) alternating with darkness

Maxillofacial

pertaining to the jaws and face

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 tonically inhibited.

Nasal Airflow/Nasal Ventilation

recording of the complete respiratory cycle by measuring inspiratory and expiratory airflow

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 REM sleep).

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.

Hypoventilation

reduced rate and depth of breathing

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

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.

Thermoregulation

regulation of body temperature in mammals

Periodic Breathing

repetitive apneic pauses, common in premature infants

Paroxysmal nocturnal dyspnea (PND)

respiratory distress and shortness of breath due to pulmonary edema, appearing suddenly and often awakening the sleeping individual.

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. .

Synchrony

scheduling sleep to synchronize with the biological clock

Hypopnea

shallow breathing in which the air flow in and out of the airway is less than half of normal--usually associated with oxygen desaturation.

Nap

short period of planned sleep generally obtained at a time separate from the major sleep period.

Sleep Stage Demarcation

significant polysomnographic characteristics that distinguish the boundaries of the sleep stages

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.

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.

Narcolepsy

sleep disorder characterized by excessive sleepiness, cataplexy, sleep paralysis, hypnogogic hallucinations, and an abnormal tendency to pass directly from wakefulness into REM sleep

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

Slow wave sleep (SWS)

sleep stages 3 and 4

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 CPAP therapy.

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 shift work.

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.

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.

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 narcolepsy.

Septoplasty

surgery on the nasal septum (dividing the nasal passage)

Tracheotomy

surgical procedure to create an opening in the trachea (windpipe) so that one can breathe

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

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.

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 with respirations..

Habitual Snorers

those who snore nearly every night

Sleep Mentation

thoughts, feelings, images, perceptions, hallucinations, and active dreams taking place during sleep

Sleep latency

time period measured from "lights out," or bedtime, to the beginning of sleep

Wake time

total time that is scored awake in a polysomnogram occurring between sleep onset and final wake-up

Chronotherapy

treatment for circadian rhythm sleep disorder by systemically changing sleeping and waking times to reset the biological clock.

K-Alpha

type of microarousal; K complex followed by several seconds of alpha rhythm.

Hyperactivity

typical behavior in a child with a sleep disorder which is causing lack of quality sleep

Hertz (Hz)

unit of frequency; equal to cycles per second (cps).

Inappropriate Sleep Episodes

unplanned sleep periods often occuring in an unsafe situation (i.e., while driving). These episodes are always due to sleep deprivation.

Nightmare

unpleasant and/or frightening dream occurring in REM sleep (different from a night terror)

Nocturnal Enuresis (Bedwetting)

urinating while asleep

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.

Twitch (Body Twitch)

very small body movement such as a local foot or finger jerk which is not usually associated with an arousal.

Sleep paralysis

waking and not being able to move for a short period of time, usually occurs out of REM (dream) sleep.

Somnambulism

walking while asleep

Shiftwork

working hours outside of the conventional daytime hours of 9:00 a.m. to 5:00 p.m.