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Electrocardiography (EKG)
A method of measuring the electrical activity of the heart.
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 tonically inhibited.
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).
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.
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.
Epworth Sleepiness Scale
Index of sleep propensity during the day as perceived by patients, and derived from the answers to 8 questions.
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
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