Sleep Procedures Overview

Overview of Overnight Sleep Study (or Polysomnography or PSG)
The most popular test performed at most sleep centers is polysomnography, or sleep study, during which a patient sleeps overnight in a special room designed to record heart function, breathing, sleepwalking and symptoms of insomnia and sleep deprivation. Using this information, a sleep expert is able to diagnose such sleep disorders as obstructive sleep apnea and move forward with the patient toward an appropriate treatment option. In the special room, several measurements are recorded, including movement of air throughout the lungs while breathing, heart rate, level of oxygen in the blood, position of the sleep person’s body, brain activity, muscle activity, eye movement and difficulty sleeping and staying asleep. Sleep Technologists observe movement and activity throughout the night, along with video cameras.

Overview of Multiple Sleep Latency Test
The Multiple Sleep Latency Test (MSLT) is a nap study used to assess how quickly a person falls asleep during the day. The test measures how much time elapses between starting to nap and the first signals of sleep, called sleep latency. Sleep centers offer multiple sleep latency testing as a way for doctors to diagnose excessive daytime sleepiness. Excessive daytime sleepiness is a condition wherein a person feels sleepy during waking hours for no apparent reason, in settings where other people are normally more awake and alert, such as at work or while driving. Diagnosable daytime sleepiness affects only about 5 percent of Americans, but it can indicate the presence of rarer sleep disorders such as narcolepsy.

The MSLT was created on the basis that a sleep doctor can measure how sleepy a person is by measuring how quickly and how often that person can fall into deep sleep during the day. As a person’s level of sleepiness increases, it theoretically takes an increasingly shorter amount of time for that person to enter rapid eye movement sleep, or REM sleep. During an MSLT, sleep doctors equip the patient to wires and sensors designed to monitor brain activity, heart rate and facial muscle movement. The end result of the MSLT is a detailed record of how quickly and how often a person is able to enter the REM stage of sleep when asked to nap during the day.

Multiple Sleep Latency Test Procedure
During a multiple sleep latency test, external factors such as temperature, noise, and light, which can make it difficult to fall asleep, are controlled as best as possible. Approximately 2 weeks before undergoing an MSLT, patients are typically asked to stop taking any regular stimulant medications.

Generally, a polysomnography or overnight sleep study will have been conducted on the night preceding the nap study. The patient has generally had at least 6 hours of monitored sleep, via the sleep study, and the MSLT serves as an expansion of the test. The MSLT is performed 1 to 3 hours after the sleep study is over, so that doctors who suspect the presence of hypersomnia or narcolepsy can gather additional information before making an official diagnosis.

During the MSLT, patients are given 4 to 5 opportunities to nap, with approximately 2-hour breaks in between each nap. If someone can’t fall asleep within 20 minutes, the test is usually cancelled, as this makes it quite unlikely that the test will lead to a diagnosis of narcolepsy or hypersomnia. Approximately 15 minutes into each nap, the patient is woken up and asked to keep active and awake until it is time for the next nap trial to begin. Once enough data is collected, the MSLT is over and the patient can leave the sleep center.

A board-certified sleep medicine physician may recommend an in-lab sleep study to:

  • Test for sleep-related breathing disorders including sleep apnea.
  • Evaluate behaviors during sleep due to parasomnias
  • Diagnose narcolepsy or hypersomnia along with the MSLT.
  • Titrate or calibrate the levels of continuous positive airway pressure in patients who receive CPAP therapy for sleep related breathing disorders.
  • Determine why treatment for a sleep disorder is not working.

For some patients suspected of obstructive sleep apnea, the sleep physician may recommend a home sleep apnea test instead of an in-lab study. A home sleep apnea test uses different equipment that you can set up yourself.
An in-lab sleep study is the way to ensure that you have the proper diagnosis for a sleep disorder. Speak with your health care provider if you think you might need a sleep study.

There are three common types of overnight sleep studies:

Diagnostic Evaluation
This study measures your sleep without any intervention. It’s typically used to diagnose or rule out a disorder

Continuous Positive Airway Pressure (CPAP) Titration
During a CPAP titration, the technologist adjusts the setting on the CPAP machine to determine how much air pressure is needed to normalize your breathing.

Split Night Study
A split night study is a combination of a diagnostic and CPAP titration study. The first half is used to diagnose sleep apnea and then midway through the night CPAP is started. The sleep tech spends the rest of the night adjusting the pressure until breathing has been normalized.

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