The American Academy Of Sleep Medicine, the governing body for sleep medicine and sleep disorders centers. www.aasmnet.org


Auto Positive Airway Pressure, a CPAP machine that automatically titrates a patient’s pressure at home. See CPAP.

Apnea/Hypopnea Index (AHI)

The frequency of abnormal respiratory events per hour of sleep as determined by an overnight polysomnogram. These events are classified as Apneas or Hypopneas. Generally, an AHI of 5-15 is considered Mild Sleep Apnea, 15-30 is Moderate, and >30 is Severe.


A cessation of breathing for 10 seconds or more, resulting in decreases in blood oxygen level and disruptions of sleep.

Arousal (Microarousal)

A change in EEG activity lasting from 2 to 15 seconds. Usually represents a shift to a higher stage of consciousness or wake.

Auto Servo Ventilation (Auto SV)

A machine used to treat complex sleep apnea and other sleep breathing disorders. Uses an algorithm to compute when a patient is not breathing and compensates.

Bedwetting (Nocturnal Enuresis)

Nighttime bedwetting usually occurs during childhood but can sometimes progress into adulthood. Its causes can be both physical and psychological.


Class of medications developed in the 1950's that tranquilize and sedate. For example, Diazepam (Valium) is a benzodiazepine.

Berlin Sleep Questionnaire

A questionnaire consisting of 10 questions in 3 categories designed to gauge the likelihood that a person suffers from sleep apnea.


Bi-level Positive Airway Pressure, Positive airway pressure like a CPAP but at two different varying pressures, one for inhalation and a lower one for exhalation.


Teeth grinding while asleep.


A sudden loss of muscle tone and reflexes that leads to muscle weakness, paralysis, or postural collapse. Usually caused by an outburst of emotion such as laughter. Considered to be one of the major 4 of symptoms of Narcolepsy.

Centimeters of water (cm H2O)

Measurement used to quantify air pressure on a CPAP.

Central Sleep Apnea (CSA)

Pauses in breathing while asleep that are not caused by an obstruction but rather by a disorder of the central nervous system.

Cheyne-Stokes Breathing

Breathing pattern with a characteristic waxing and waning appearance. Usually related to heart conditions.

Chronic Insomnia

Insomnia that continues beyond the occasional occurrence.

Circadian Rhythm

The body’s 24 hour cycle of sleep and wake. It is related to exposure to light and shifts in hormone levels.

Complex Sleep Apnea

Sleep apnea that displays both obstructive and central characteristics.

CPAP Humidification

Moisture added to the airflow during CPAP therapy. Humidification is an important part of CPAP, preventing the patient’s airway from becoming too dry during the night.


Continuous Positive Airway Pressure, a machine that creates a pneumatic split of a person’s airway. A CPAP is generally interfaced with the patient by way of a nasal breathing mask; this mask is worn during sleep and delivers pressurized air to keep the person’s airway from collapsing as a result of obstructive sleep apnea.

Deep Sleep

The combined non-REM sleep stages 3 and 4 in polysomnograms. Deep Sleep is especially important to repair body tissue and is often when important hormones are released during sleep.

Durable Medical Equipment (DME)

Medical equipment prescribed for use by or on the order of a physician, also includes CPAP and BI-Level machines. Many facilities, such as Oregon Sleep Associates, have an on-site DME service.

Electrocardiogram (EKG, ECG)

A recording of the electrical activity of the heart.

Electroencephalogram (EEG)

A recording of the electrical activity of the Brain e.g. brainwaves.

Excessive Daytime Sleepiness (EDS)

Feeling of excessive sleepiness during the day. Often measured by using a subjective assessment such as the Epworth Sleepiness Scale.

Full Face Mask

CPAP mask covering the nose and mouth, helps when patients on CPAP are mouth breathing.

Gastroesophageal Reflux Disease (GERD)

Movement of stomach acid up into the esophagus. Positional therapy during the night can help lessen the effects of GERD.

Home Sleep Testing

Sleep testing conducted by an accredited sleep center but carried out at home using portable monitoring. Should only be used in certain cases when the patient has been evaluated as needing it by a board certified sleep specialist.


Excessive, prolonged sleep. May be a symptom of an underlying sleep disorder.

Hypnagogic Jerks (Hypnic Jerks)

Normal involuntary kicks or jerks of the legs that occur as a person falls asleep.

Hypnogogic Hallucinations

Vivid, frightening, dream-like experiences that occur in the transition from wake to sleep. Can be a symptom of Narcolepsy.


Sleep-inducing drugs or substances.


A reduction or obstruction in nocturnal breathing for at least 10 seconds results in decrease in blood oxygen level and disrupts sleep.


Newer class of compounds used to induce sleepiness. For example, Zolpidem (Ambien) is an Imadaopyridine.


The inability to initiate or maintain sleep.

Jet Lag

Condition caused by the body trying to adapt to rapid changes in time zones while traveling. Symptoms include hypersomnia, insomnia, depression, and fatigue.

Light Therapy

Therapy involving exposure to intense light for a certain duration of time to help regulate the sleep/wake cycle. Light Therapy is used in the treatment of SAD (Seasonal Affective Disorder) and other conditions.

Maintenance of Wakefulness Test (MWT)

Test used to prove whether a person can stay awake during the day. Usually conducted on workers that have a job where vigilance is requires i.e. truck drivers, safety workers, etc.


A hormone secreted in the body to help regulate the sleep/wake cycle. Studies have been inconclusive as to whether taking Melatonin supplements has any real benefit on sleep.

Multiple sleep latency test (MSLT)

A sleep test consisting of a series of 4 to 5 naps during the day after a nocturnal polysomnogram. The MSLT is used to help diagnose Narcolepsy and other disorders of excessive daytime sleepiness.


Sleep disorder characterized by excessive sleepiness, cataplexy, sleep paralysis, hypnagogic hallucinations, and an abnormal tendency to pass directly from wakefulness into REM sleep. Narcolepsy’s causes are not fully known, but may be related to a deficiency of certain neurotransmitters in the brain.

Nasal Mask

CPAP mask that covers the nose only.

Nasal Pillows

CPAP mask that covers only the nostril openings.

Night Terrors

Night terrors are characterized by an incomplete arousal from slow wave sleep. Generally, they occur mostly during childhood and adolescence. The patient may scream out or act frightened during the night terror, but usually has no recollection of the event if awakened.


Frightening dream that may be disturbing enough to cause the patient of wake from sleep. These differ from night terror in that they usually occur during REM sleep rather than non-REM and many times the patient retains recollection of the event.


Frequent urination during the night, may be a sign of underlying sleep disorders.

Obstructive Sleep Apnea (OSA)

A sleep disorder that affects almost 25% of the population. In OSA a person’s airway tissue including the tongue, soft palate, and pharynx relax or collapse during sleep. This leads to obstruction of the airway and lack of oxygen to the lungs. After a period of fighting to breathe, sometimes as long as 2 minutes, the person briefly arouses from sleep and regains airway muscle tone. Obstructive Sleep Apnea is a very serious condition with connections to obesity, diabetes, heart disease, and stroke.

Periodic Limb Movement Syndrome (PLMD)

A disorder where a person moves or twitches their limbs involuntarily during sleep. These movements can disrupt their sleep and the sleep of those around them.

Polysomnogram (PSG)

A recording of sleep, a sleep study usually performed in a sleep center. Polysomnograms involve hooking a patient up to recording sensors that monitor breathing, heart rate, movement, brainwaves, etc. This test is the gold standard for diagnosing sleep disorders.


The study of sleep.

Pressure Transducer

A pressure transducer is a device used to observe a person’s breathing function by sampling the changes in pressure during inhalation and exhalation. This device is used to help diagnose Sleep Apnea during a polysomnogram.

Radiofrequency Procedure (Somnoplasty)

Medical procedure for treating nasal obstruction, snoring and in some cases, sleep apnea. Somnoplasty uses radio wave energy to reduce snoring and the size of the soft palate, but generally is ineffective in treating Obstructive Sleep Apnea (OSA).

REM Behavior Disorder (RBD)

A disorder characterized by acting out of a person’s dreams physically while the patient remains asleep. These episodes can be quite vivid and even dangerous to the dreamer and to those around them.


A stage of sleep that occurs 4 to 5 times per night on average characterized by decrease in body muscle tone and a marked increase Rapid Eye Movements. During this stage, the brain becomes more active than the other stages of sleep. It is commonly believed to be when a person dreams the most and might have connections to memory functions. In a patient with Sleep Apnea, REM usually produces the most severe breathing events.

Restless Legs Syndrome (RLS)

A condition marked by the extreme urge of needing to move one’s legs during times of rest. The feeling is usually temporarily relieved by movement but can disrupt sleep and relaxation time.

Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder, a seasonal shift to depression and excessive sleepiness during the winter months. SAD is related to a lack of exposure to sunlight and shorter daylight hours.

Sleep Debt

The result of sleep deprivation in which an individual does not experience a feeling of being rested or refreshed.

Sleep Hygiene

Practices that aid in falling asleep or maintaining sleep. Examples include a calming bedtime ritual, a quiet environment, and removal of televisions or computers from the bedroom.

Sleep Maintenance Insomnia

Inability to maintain sleep throughout the night.

Sleep Onset Insomnia

Inability to initiate sleep

Sleep Paralysis

Brief muscle atonia or paralysis that occurs upon falling asleep or awakening. Related to the normal atonia that occurs during REM sleep, this condition can be a sign of Narcolepsy.

Sleep talking

Talking that occurs during sleep as the result of a motor breakthrough during a dream in REM stage sleep or from an arousal out of non-REM sleep. Full consciousness is not achieved and generally the patient has no recollection of the event.


Walking while asleep. Usually occurs during deep sleep and is not necessarily related to dreaming. Contrary to popular belief, waking someone who is sleepwalking will not do them harm.


Loud noise produced with breathing during sleep. Caused by 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.


Prolonged drowsiness or sleepiness.


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

Transient Insomnia

Insomnia that is temporary, usually connected to a stressful time or event. When the stress ends usually the insomnia stops.

Uvulopalatopharyngoplasty (UPPP)

Operation performed on the throat to treat snoring and sleep apnea. During UPPP portions of the airway are surgically removed, including the uvula, tonsils, adenoids, and tissue of the soft palate. This is done to physically open the airway. UPPP is an accepted means of surgical treatment has a curative rate of less than 50%.