Polysomnography (PSG) – AKA Sleep Study or Sleep Test

The word Polysomnography is derived from the Greek word ‘polus’ for “many, much”, the Latin word ‘somnus’ meaning “sleep” and the Greek word ‘graphein’ meaning to write “to write”. When a patient feels that they have some sleeping problems or sleep disorders they may consult a doctor, health practitioner or specialist for diagnosis. To confirm an initial diagnosis a patient may be referred to a Chicago sleep clinic for a Polysomnogram sleep study or sleep test.

A sleep test is used as a diagnostic tool in sleep medicine. A Polysomnography (PSG) test is the most common multi-parametric test used in the study of sleep. Approximately 50 – 80 million Americans are reportedly affected by Sleep Deprivation, and/or Sleep Related Breathing Disorders. A large proportion of patients are not diagnosed either.

A polysomnogram sleep study will typically record a minimum of 11 channels requiring a minimum of 22 wire attachments to the patient (please refer to figure A). Electrodes are attached to the chin, the scalp and the outer edge of the eyelids. Monitors attached to the chest record the heart rate and breathing. Click here to view a sample polysomnogram sleep study.


A Polysomnogram sleep test measures sleep cycles and stages of sleep (please refer to figure B) and monitors and records the following elements:

  • Sleep patterns and stages
  • Blood oxygen levels
  • Body position
  • Brain waves (EEG)
  • Breathing rate
  • Electrical activity of muscles
  • Eye movements
  • Leg movements
  • Heart rate

Sleep studies or tests are conducted to confirm and gain additional information about a patient’s sleep problems. A Polysomnogram might be used to confirm or detect any of the following conditions:

  • Obstructive Sleep Apnea
  • Central Sleep Apnea
  • Insomnia
  • Narcolepsy
  • Periodic limb movement disorder (PLMD)
  • Excessive daytime sleepiness (EDS)
  • Hypersomnia
  • REM sleep disorder

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