Sleep Disorders Glossary E

Sleep Disorders Glossary - E

Electrocardiography [EKG] [ECG]

Electrocardiography is a commonly used, noninvasive procedure for recording electrical changes in the heart. The record, which is called an electrocardiogram (ECG or EKG), shows the series of waves that relate to the electrical impulses that occur during each beat of the heart.


Electrodes are small devices that send brain waves or other biological electrical signals from a patient to a polysomnogram machine, where the signal is amplified and displayed.

Electroencephalogram [EEG]

Electroencephalogram is the record of the electrical activity of the brain. Electroencephalograms are useful in studying and detecting brain disorders.

Characteristic frequency and amplitude patterns of the activity define which stage of sleep the patient is experiencing. Brain waves are recorded in both diagnostic and CPAP titration sleep studies.

Electromyogram [EMG]

An electromyogram (EMG) is a test that is used to record the electrical activity of muscles. When muscles are active, they produce an electrical current. This current is usually proportional to the level of the muscle activity. An EMG is also referred to as a Myogram.

Electrooculogram [EOG]

Electrooculogram is a recording of the resting potential of the retina. The main applications are in ophthalmological diagnosis and in recording eye movements. As opposed to the electroretinogram, the EOG does not represent the response to individual visual stimuli.

Endogenous Circadian Pacemaker

Endogenous circadian pacemaker in an internal mechanism in the brain, thought to be at the site of the suprachiasmatic nucleus, that drives periodic processes, such as the sleep-wake cycle, cortisol release, and body temperature, in the circadian timing system of humans.

Endocrine system

Endocrine system is body control system composed of a group of glands that maintain a stable internal environment by producing chemical regulatory substances called hormones.

Endogenous rhythms

Endogenous rhythms are the rhythms driven by an internal, self-sustaining biological clock rather than by signals that are external to the organism.


Entrain to rearrange or align with the biological clock.


Enuresis is also called bed-wetting or sleep enuresis, is the involuntary passage of urine while asleep. Inherent in the definition of NE is satisfactory bladder control while the child is awake.


Epidemiology is t he study of the distribution and determinants of health-related states and events in populations and the control of health problems, the study of epidemic disease.


Epilepsy is a neurological disorder involving repeated seizures. A seizure, also called convulsion, is a sudden change in behavior caused by increased electrical activity in the brain. The increase in electrical activity may result in unconsciousness and violent body shakes or simply a staring spell that may go unseen.


Epoch is a standard 30-second page of the sleep recording that is allocated a sleep stage description; occasionally, for particular purposes, longer or shorter epochs are scored.

Epworth sleepiness scale

Epworth Sleepiness Scale is an index of sleep propensity during the day as perceived by patients, and derived from the answers to 8 questions. The scale was developed by researchers in Australia and is widely used by sleep professionals around the world to measure sleep deprivation.

Esophageal Pressure

Esophageal Pressure is a measurement used to determine respiratory effort and by inference, airway resistance. Considered an invasive measure, it is sometimes used in polysomnogram testing.

Excessive daytime Sleepiness / EDS/ Somnolence / Hypersomnia

Excessive daytime sleepiness is also called excessive sleepiness or EDS or Somnolence or Hypersomnia, refers to either excessive sleepiness during the day or extended, overly long periods of nighttime sleep. It may be associated with difficulty in awakening.

Expiratory Phase

Expiratory Phase is the phase of the breathing cycle in which air is expelled.

Expiratory Positive Airway Pressure/EPAP

Expiratory Positive Airway Pressure is the pressure prescribed for the expiratory phase of an individual on Bi-level CPAP therapy for obstructive sleep apnea. It is also referred as EPAP.

Exogenous Rhythms

Exogenous rhythms are the rhythms that are directly regulated by an external influence, such as an environmental cue.


All Article Categories