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Abdominal 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 intrusion
Brief occurrence of alpha activity during a stage of sleep.
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.
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 per hour.
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 cardiac tissue.
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.
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