What To Expect During a Sleep Study

Sleep studies are painless. Parents can go with their children to a sleep study.

The polysomnogram (PSG), multiple sleep latency test (MSLT), and maintenance of wakefulness test (MWT) are usually done at a sleep center. The room the sleep study is done in may look like a hotel room. A technician makes the room comfortable for you and sets the temperature to your liking.

Most of your contact at the sleep center will be with nurses or technicians. You can ask them any questions that you may have about the sleep study.

During a Polysomnogram

Sticky patches called sensors are placed on your scalp, face, chest, limbs, and a finger. While you sleep, these devices record your brain activity, eye movements, heart rate and rhythm, blood pressure, and the amount of oxygen in your blood.

Elastic belts are placed around your chest and abdomen. They measure chest movements and the strength and duration of each exhaled breath.

Wires attached to the sensors transmit the data to a computer in the next room. The wires are very thin and flexible and are bundled together to minimize discomfort. You will be able to roll in any direction.

A technician in another room monitors the recordings as you sleep. He or she fixes any problems with the recordings that occur.

The technician also helps keep you comfortable and disconnects the equipment if you need to go to the bathroom.

When it's time for you to sleep, the room will be dark and quiet.

If you show signs of sleep apnea, you may have a split-night sleep study. During the first half of the night, the technician records your sleep patterns. At the start of the second half of the night, he or she wakes you to fit a continuous positive airway pressure (CPAP) mask over your nose and mouth.

The mask is connected to a small machine that gently blows air through the mask. This creates mild pressure that keeps your airways open while you sleep.

The technician checks how you sleep with the CPAP machine. He or she adjusts the flow of air through the mask to find the setting that's right for you.

At the end of the PSG, the technician helps you out of bed and removes the sensors. If you're having a daytime sleep study, such as an MSLT, some of the sensors may be left on for that test.

During a Multiple Sleep Latency Test

The MSLT is a daytime sleep study that's usually done after a PSG. Sensors on your scalp, face, and chin usually are used for this test. These sensors record brain activity. They show various stages of sleep and how long it takes you to fall asleep. Sometimes your breathing also is checked during an MSLT.

A technician in another room watches these recordings as you sleep. He or she fixes any problems with the recordings that occur.

Starting 1.5 to 3 hours after you wake from the PSG, you're asked to relax in a quiet room for about 30 minutes. The test is repeated three or four times throughout the day. This is because your ability to fall asleep changes throughout the day.

You get 2-hour breaks between tests. You need to stay awake during the breaks.

The MSLT records whether you fall asleep during the test and what types and stages of sleep you have. Sleep has two basic types: rapid eye movement (REM) and non-REM. Non-REM sleep has four distinct stages. REM sleep and the four stages of non-REM sleep occur in patterns throughout the night.

The types and stages of sleep can help your doctor diagnose a sleep disorder such as narcolepsy, idiopathic hypersomnia, or a circadian rhythm disorder.

During a Maintenance of Wakefulness Test

This sleep study occurs during the day. It's usually done after a PSG and takes most of the day. Sensors on your scalp, face, and chin are used to measure when you're awake or asleep.

You sit quietly on a bed in a comfortable position and look straight ahead. Then, you simply try to stay awake for a period of time.

An MWT typically includes four trials lasting about 40 minutes each. If you fall asleep, the technician will wake you after about 90 seconds. There are usually 2-hour breaks between trials. During these breaks, you can read, watch television, etc.

If you're being tested as a requirement for a transportation- or safety-related job, you may need a drug-screening test before the MWT.

During an Actigraph Test

You don't have to go to a sleep center for this study. The actigraph is a small device that's usually worn like a wristwatch. You can go about your normal daily routine while you wear it. You remove it while swimming or bathing.

The actigraph measures your sleep–wake behavior over 3 to 7 days. Results give your doctor a better idea about your sleep habits, such as when you sleep or nap and whether the lights are on while you sleep.

You may be asked to keep a sleep diary while you wear the actigraph.