Polysomnography is a sleep study. A sleep study monitors you as you sleep, or try to sleep.

There are two states of sleep:

• Rapid eye movement (REM) sleep
• Non-rapid eye movement (NREM) sleep

REM sleep is associated with dreaming. Your body muscles (except your eyes and lungs) do not move during this stage of sleep.

NREM sleep has four stages that can be detected by brain electrical activity (EEG) waves.

REM sleep alternates with NREM sleep approximately every 90 minutes. A person with normal sleep usually has four to five cycles of REM and NREM sleep during a night.

A sleep study measures your sleep cycles and stages by recording the following information:

• Air flow in and out of the lungs during breathing
• Blood oxygen levels
• Body position
• Brain waves (EEG)
• Breathing effort and rate
• Electrical activity of muscles
• Eye movement
• Heart rate

Sleep study; Polysomnogram; Rapid eye movement studies

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Sleep studies

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Review Date: 09/15/2010
Reviewed By: Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)