ABOHNS Sleep Medicine key terms

The average number of apneas plus hypopneas per hour of sleep, calculated by dividing the total event count by total sleep time; the primary metric used to grade obstructive sleep apnea severity.

A partial upper airway obstruction event marked by a reduction in airflow lasting at least ten seconds, usually scored when accompanied by a defined oxygen desaturation or an arousal from sleep.

The number of oxygen desaturations of a specified depth per hour of recording, often used as a surrogate marker of sleep-disordered breathing when airflow signals are unavailable or unreliable.

An EEG arousal following a respiratory event that does not meet hypopnea criteria, signifying clinically relevant airway obstruction and fragmented sleep even when the AHI appears low.

A condition of excessive daytime sleepiness and sleep fragmentation caused by increased breathing effort against a narrow airway, without meeting standard apnea or hypopnea thresholds.

Unattended recording of respiratory and oximetric signals in the patient's home, used to diagnose obstructive sleep apnea in selected adults with a high pretest probability and no significant comorbidity.

An attended overnight laboratory study recording EEG, eye movements, muscle tone, airflow, respiratory effort, oxygen saturation, ECG, and body position to stage sleep and quantify sleep disorders.

Total sleep time divided by total time in bed, expressed as a percentage; a measure of sleep continuity that falls in insomnia and in many medical and psychiatric disorders.

The interval from lights out to the first epoch of sleep, used to characterize insomnia, circadian phase, and excessive daytime sleepiness in laboratory testing.

A daytime series of nap opportunities performed after overnight polysomnography that measures mean sleep latency and the presence of sleep-onset REM periods to support a diagnosis of narcolepsy.

A daytime protocol in which the patient attempts to remain awake in a quiet setting across several trials, used to assess ability to sustain wakefulness rather than propensity to fall asleep.

The appearance of rapid eye movement sleep within about fifteen minutes of sleep onset, a hallmark of narcolepsy and also seen in some other conditions and with certain medications.

A central hypersomnia caused by loss of hypothalamic orexin neurons, producing excessive sleepiness plus cataplexy and supported by low cerebrospinal fluid orexin levels.

A sudden, brief loss of skeletal muscle tone triggered by strong emotion such as laughter, occurring while awake and considered the most specific clinical feature of narcolepsy type 1.

A hypothalamic neuropeptide that stabilizes wakefulness and suppresses REM sleep; its deficiency in cerebrospinal fluid supports the diagnosis of narcolepsy type 1.

An inability to maintain wakefulness during the day, with unintended lapses into sleep or drowsiness that impairs function; a symptom requiring evaluation for sleep deprivation, apnea, medications, and central causes.

A validated eight-item self-report questionnaire rating the likelihood of dozing in common situations, producing a score from zero to twenty-four used to quantify subjective daytime sleepiness.

Repetitive collapse or narrowing of the pharyngeal airway during sleep causing apneas, hypopneas, oxygen desaturation, and arousals, typically with continued or increased respiratory effort.

Cessation of airflow during sleep without respiratory effort, arising from absent or unstable central ventilatory drive rather than upper airway obstruction.

A cyclic breathing pattern of crescendo-decrescendo tidal volume separated by central apneas or hypopneas, commonly seen in heart failure and associated with high loop gain.

A measure of the sensitivity and speed of the ventilatory control system's response to a disturbance; high loop gain promotes unstable breathing and central apneas during sleep.

Daytime hypercapnia with a body mass index of at least thirty in the absence of other causes of hypoventilation, often accompanied by obstructive sleep apnea and requiring bilevel ventilatory support.

A device that delivers pressurized air through a nasal or oronasal interface to splint the upper airway open during sleep, the first-line therapy for moderate to severe obstructive sleep apnea.

The degree to which a patient uses prescribed positive airway pressure, conventionally judged adequate at four or more hours per night on most nights, which determines whether insurance continues to cover therapy.

An implanted device that delivers electrical stimulation to the hypoglossal nerve during inspiration, stiffening the tongue and enlarging the pharyngeal airway; an option for selected patients intolerant of positive airway pressure.

Endoscopic evaluation of the upper airway under light sedation that reproduces sleep-like collapse, used to characterize the pattern and level of obstruction before selecting surgical or device therapy.

A surgical procedure removing or reshaping the uvula, soft palate, and tonsillar pillars to enlarge the retropalatal airway; outcomes depend heavily on the site and pattern of obstruction.

A bedside grading of oropharyngeal visibility with the mouth open and tongue protruded, from class one to four, used as one component of airway risk assessment.

An eight-item screening tool for obstructive sleep apnea based on snoring, tiredness, observed apneas, pressure, body mass index, age, neck circumference, and gender.

The elevated likelihood of airway complications, difficult intubation, and postoperative respiratory events in patients with untreated sleep-disordered breathing, guiding monitoring and planning of anesthesia.

A clinical situation in which mask ventilation, laryngoscopy, supraglottic device placement, or intubation is unexpectedly hard, with risk increased by obesity, craniofacial features, and obstructive sleep apnea.

Sleep-disordered breathing in children, most often caused by adenotonsillar hypertrophy, presenting with snoring, labored breathing, restless sleep, and daytime behavioral or learning problems rather than classic adult sleepiness.

Surgical removal of the tonsils and adenoids, the first-line treatment for most children with obstructive sleep apnea; residual disease may persist, particularly in obese children.

Inward movement of the chest wall during inspiration, reflecting increased respiratory effort against an obstructed airway and commonly observed in children with sleep-disordered breathing.

A structured, evidence-based treatment combining sleep restriction, stimulus control, cognitive restructuring, and education to change behaviors and beliefs that maintain insomnia; first-line therapy for chronic insomnia.

Persistent difficulty initiating or maintaining sleep, or early awakening, with adequate opportunity to sleep and associated daytime impairment lasting at least three months for the chronic form.

A behavioral treatment that limits time in bed to approximate actual sleep time, then gradually extends it as sleep efficiency improves, reducing the mismatch between time in bed and sleep.

A misalignment between the internal circadian timing system and the external day-night schedule, producing insomnia or excessive sleepiness that resolves when the schedule is shifted.

The time in the evening when melatonin secretion rises under dim light, used as a marker of circadian phase to assess whether a patient's internal clock is advanced or delayed.

A circadian disorder in which sleep timing is shifted late relative to social demands, causing difficulty falling asleep and difficulty waking, most common in adolescents and young adults.

A parasomnia in which normal muscle atonia during REM sleep is lost, so dreams are acted out with talking, thrashing, or injury; often a harbinger of synucleinopathy.

The polysomnographic finding of elevated chin muscle tone during REM sleep, the physiological substrate of REM sleep behavior disorder and a required supportive feature for its diagnosis.

Disorders of arousal such as sleepwalking, sleep terrors, and confusional arousals that arise from deep non-REM sleep, often with partial awakening, confusion, and amnesia for the event.

Recurrent episodes of eating and drinking after an arousal from sleep, often with partial awareness and later amnesia, classified among the non-REM arousal parasomnias.

An urge to move the legs, usually with uncomfortable sensations, that worsens at rest and in the evening and is relieved by movement; frequently associated with iron deficiency.

Repetitive, stereotyped limb movements during sleep, typically every twenty to forty seconds, scored by polysomnography and often coexisting with restless legs syndrome.

A wrist-worn motion sensor that estimates sleep-wake patterns over days to weeks, useful for assessing circadian rhythm, insomnia patterns, and total sleep time when history is uncertain.

Sustained elevation of carbon dioxide during sleep detected by blood gas or surrogate measures, caused by hypoventilation from lung disease, neuromuscular weakness, obesity, or central drive problems.

An abrupt shift in EEG frequency lasting at least three seconds during sleep, reflecting brief activation of the brain and contributing to sleep fragmentation when frequent.