Polysomnography

Polysomnography or PSG is the multi-parametric test used in the study of sleep. The name is derived from Greek roots: 'Poly' (many), 'somno' (sleep), and 'graphy' (writing).

Normal patterns of human sleep were first discovered by Loomis, Harvey and Hobart in 1935. In 1952, the discovery and doccumentation of REM (Rapid Eye Movement) sleep was accomplished by Eugene Aserinsky, Nathaniel Kleitman and graduate students at the University of Chicago in the 1950s, it has since been codified by the adoption in 1968 of A Manual of Standardized Terminology, Techniques, and Scoring Systems for Sleep Stages of Human Subjects, edited by Allan Rechtschaffen and Anthony Kales.

Eventhough Aserinsky and Kleitman's discovery of REM sleep was published in 1953, no other sleep laboratory findings were published until 1959.

Polysomnography is a comprehensive recording of the biophysiological changes that occur during sleep. Ploysomnography is usually performed at night during sleep. This diagnostic test monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG),heart rhythm (ECG), and breathing function or respiratory effort during sleep. In the 1970s, respiratory airflow and respiratory effort indicators were added along with peripheral pulse oximetry following the identification of the sleep disorder Sleep apnea. Polysomnography is used to diagnose many types of sleep disorders including narcolepsy, restless legs syndrome, REM behavior disorder, parasomnias, and sleep apnea.

Increasingly Polysomnography is being supplemented or replaced by Actigraphy in cases where longitudinal or large scale data sets need to be generated, or when PSG is not a cost efficient option

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