| Subject | Contents |
| Definition | A test of sleep cycles and stages through the use of continuous recordings of brain waves ( EEG ), electrical activity of muscles, eye movement (electrooculogram), respiratory rate, blood pressure , blood oxygen saturation, and heart rhythm and direct observation of the person during sleep. There are 2 states of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. REM sleep is associated with dreaming and generalized muscle paralysis sparing the eye muscles and diaphragm. NREM sleep has 4 stages distinguishable by EEG waves. REM sleep alternates with NREM sleep approximately every 90 minutes. A person with normal sleep usually has 4 to 5 cycles of REM and NREM sleep during a night. |
| Alternative Names | Sleep studies; Polysomnography; Rapid eye movement studies |
| How the test is performed | Polysomnograms may be conducted in a sleep study center. You will lie on a bed in the test center. The test may be carried out during the night so that normal sleep patterns can be reproduced. Electrodes are placed on the scalp, the outer edge of the eyelids, and to the skin on the chin in preparation for the test. Characteristic patterns from the electrodes are recorded during wakefulness with the eyes closed and during sleep. The time taken to fall asleep is measured as well as the time to enter REM sleep. Sometimes the movements of a person during sleep are recorded by video camera. |
| How to prepare for the test | Do not take any sleeping medication and do not drink alcohol or caffeine-containing beverages before the test. Infants and children: The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:preschooler test or procedure preparation (3 to 6 years) schoolage test or procedure preparation (6 to 12 years) adolescent test or procedure preparation (12 to 18 years) |
| How the test will feel | Electrodes will be placed on the skin and scalp. Monitors to record heart rate and respiratory rate (breathing) will be attached to the chest. Sometimes other test to determine breathing disorders during sleep are also performed. |
| Why the test is performed | The test is performed for insomnia , excessive daytime sleepiness , obstructive sleep apnea , breathing difficulties during sleep, or behavior disturbances during sleep. |
| Normal Values | Usual or normal patterns of brain waves and muscle movements during sleep. |
| What abnormal results mean | Abnormal results may confirm suspected sleep disorders such as insomnia , hypersomnia , obstructive sleep apnea , and narcolepsy . |
| What the risks are | The risks are negligible as long as the tests and equipment are appropriately supervised. |
| Special considerations | Sleep studies may be applied to other disorders. |
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