Sleep Laboratory Evaluation - Evaluation Of Sleep Disturbances: Sleep Disorders

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Sleep laboratory evaluation

Most people with sleep problems don't need to visit a sleep laboratory. Insomnia and circadian rhythm disorders, for example, can be diagnosed by a thorough history and physical examination. However, when a doctor suspects a sleep disorder such as narcolepsy (see "Narcolepsy"), periodic limb movement disorder (see "Movement disorders in sleep"), sleep apnea (see "Sleep apnea"), or one of the parasomnias (see "Sleepwalking and other parasomnias"), he or she may recommend formal sleep testing.

Fees depend on the level of testing required. Some people require a one-time consultation with a sleep specialist, which may run a few hundred dollars. Staying overnight in a sleep laboratory costs between $800 and $1,500. It's important to check with your insurance company in advance because reimbursement varies and may depend on your diagnosis.

The American Academy of Sleep Medicine has a listing of more than 700 accredited sleep disorder centers and more than 2,600 board-certified sleep specialists (see "Resources"). Some centers will make an appointment directly with you, while others require a physician referral. The center will request medical records and may send you a sleep questionnaire or diary to use before your visit. You may also be asked to change your sleep habits in certain ways before scheduling the visit. Sometimes these changes alone correct the problem.

Overnight sleep tests

When you spend the night in a sleep laboratory, you'll wear your own nightclothes and you can use a pillow from home. You can use your regular medications, but the clinicians will need to know what they are. The lab usually provides a regular bed in a private room with a bathroom attached. The room is kept as quiet as is possible.

Polysomnography is commonly performed in sleep labs to monitor patients' sleep. For this procedure, small electrodes, placed on the scalp and other parts of the body, take readings during the night. Lab staff examine the readings from a nearby control room.

After a technician sets up the sleep-monitoring equipment, you'll be left alone to relax until bedtime. Throughout the night, laboratory staff will monitor the instruments in a nearby control room. Some of the tests and equipment used include polysomnography, audio- and videotape, and daytime sleep tests.

Polysomnography. In this procedure, small wafer-thin electrodes and other sensors are pasted on specific body sites to take a variety of readings during the night. They may be placed on your scalp to track brain waves; under your chin to measure fluctuations in muscle tension (called an electromyogram or EMG); near your eyes to measure eye movements; near your nostrils to measure airflow; on your earlobe or finger to measure the amount of oxygen in your blood (using a device called an oximeter); on your chest or back to record heart rate and rhythm; on your legs to record twitches or jerks; and over your rib muscles or around the rib cage and abdomen to monitor breathing.

Readings are collected on a single printout (called a polysomnogram) and analyzed by a technician and physician. If a breathing problem is detected early on, you may be awakened and given treatment, such as CPAP (see "Treatments for apnea"), during the second half of the night. This allows the sleep experts to monitor how well the treatment works for you. Sometimes this process requires two nights. A standard polysomnogram cannot diagnose sleep-related epilepsy. If your doctor suspects that you may have a seizure disorder, you may undergo a full electroencephalogram (EEG) during the night.

Audio- and videotape. Audiotape equipment may be used to record snoring, talking during sleep, or other sounds. A video may also be taken to compare with the polysomnogram. This may show, for example, that you snore only when in a certain position. Signs of movement disorders (such as periodic limb movement disorder) or parasomnias will probably be apparent on the videotape.

Daytime sleep tests. Daytime sleep tests may be administered after a night in the sleep lab. The multiple sleep latency test measures how long it takes you to fall asleep while lying down in a quiet room and what stages of sleep occur during a brief nap. The procedure is usually repeated four or more times during the day at two-hour intervals. This test measures sleepiness and looks for signs of narcolepsy. Falling asleep within five minutes each time indicates extreme sleepiness.

In the maintenance of wakefulness test, which is less commonly used, you're given the opposite instructions: Try to stay awake. This ability is also affected by the degree of sleepiness. People are sometimes given both tests at different times.

Last updated:	January 23, 2007