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Types of Sleep Studies

Memorial Hermann Sleep Centers perform Polysomnograms (overnight sleep studies), Multiple Sleep Latency Tests (MSLT), and Maintenance Wakefulness Tests for the diagnosis of:

  • Sleep apnea
  • Sleep-related breathing disorders
  • Narcolepsy
  • Insomnia
  • Periodic limb movement disorder
  • Night terrors
  • Sleep walking/sleep talking
  • REM behavior disorder
  • Hyper somnolence
  • Sleep-wake schedule disruption
  • Nocturnal oxygenation problems
  • Difficulty maintaining sleep
  • Unusual behavior during sleep

Physiological parameters monitored include:

  • Respiratory effort and intercostals EMG
  • Air flow by thermistor, nasal pressure orexpired CO2
  • EEG (central and occipital)
  • EOG (electro-oculogram to monitor eye movement)
  • EMG (anterior tibialis, submental and intercostal)
  • ECG
  • SaO2
  • Arm EMG can be performed upon request with adequate notification

We perform the following sleep studies in Houston:

Overnight Sleep Studies

Memorial Hermann Southeast Hospital's Sleep Disorders Center performs the following overnight studies (daytime tests may be scheduled for shift workers):

 

Nocturnal Polysomnogram

The nocturnal polysomnogram (NPSG) is considered the “gold standard” tool for use in diagnosing sleep disorders. The NPSG is commonly ordered for patients with excessive daytime sleepiness, snoring, sleep apnea, insomnia, morning headaches, chronic fatigue, REM behavior disorder and parasomnias that include night terrors, nightmares, sleep walking and bed wetting. Specific information about preparing for an overnight sleep study is available.

Nocturnal Polysomnogram with CPAP

The NPSG with continuous positive airway pressure (CPAP) is performed for treatment of obstructive and mixed sleep apnea, upper airway resistance syndrome and snoring. CPAP systems consist of an airflow generator, air tubing and a nasal mask. Air pushed from the generator through the tubing and mask passes through your nose and into your throat, where the slight pressure keeps your upper airway open without interfering with breathing. CPAP is considered the most effective noninvasive treatment for obstructive sleep apnea (OSA).

Nocturnal Polysomnogram with BiPAP

The NPSG with BiPAP is performed with people who have difficulty tolerating the NPSG with CPAP or who have a CPAP pressure of higher than 17 cm/H2O. Bilevel therapy works by delivering two different levels of positive air pressure: a higher level of pressure when you inhale and a lower level of pressure when you exhale. BiPAP devices can help people with obstructive sleep apnea (OSA) if they have found CPAP therapy too difficult.

Split Night Sleep Study

The split night sleep study is used to initiate quick treatment for severe obstructive sleep apnea (OSA). The study consists of two parts: diagnostic tests are performed during the first half of the night and if obstructive sleep apnea is clearly evident, treatment involving the nasal CPAP is administered during the second half of the night. CPAP is administered using an airflow generator, air tubing and a nasal mask. Air pushed from the generator through the tubing and mask passes through your nose and into your throat, which the slight pressure keeps your upper airway open without interfering with breathing. CPAP is considered the most effective noninvasive treatment for obstructive sleep apnea. Call the Sleep Lab for specific criteria for the split night sleep study.

Multiple Sleep Latency Test (MSLT)

The multiple sleep latency test is a recording of brain waves, eye movements and muscle activity and EKG during five 20-minute nap periods scheduled throughout the day in two-hour intervals. Used to rule out narcolepsy, cataplexy and idiopathic hypersomnolence, the MSLT can accurately assess daytime sleepiness by measuring the length of time required to fall asleep during each nap (sleep latency).

It also measures rapid eye movement (REM) sleep (or dreaming) and the latency to REM sleep on each nap. By sampling sleep latency five times during the day, we can obtain a profile of your daytime sleepiness.

 

When is an MSLT indicated?

An MSLT is indicated for people with complaints of excessive daytime sleepiness or with a history of falling asleep inappropriately during the day. An MSLT is especially important for people whose polysomnogram overnight study results were normal, but who continue to experience daytime sleepiness, for example, people with narcolepsy.

Usually, the MSLT is scheduled the day after the overnight study, in which case you'll remain in the hospital throughout the test (the entire night and the following day). Some of the electrodes used in your overnight study will be removed, while those on the head and around the eyes, chin and the chest will be left on for the MSLT.

What about medications?

Since an MSLT is very sensitive to certain types of medication such as stimulants or antidepressants, you'll be instructed on their use or withdrawal well before the date of your study, by your physician.

Should I stay awake between nap periods?

It is important that you try to stay awake throughout the day of your test, except during nap periods. Therefore, when your overnight study is completed, you'll be asked to remain out of bed until the time of the first nap. You'll also be asked to stay up between successive naps throughout the day (approximately two hours apart). You may read, walk, eat regular meals (without caffeine) for the duration of your stay in the hospital. You may want to bring a book or something to keep you occupied during the day. Meals will be provided during the nap study.

Maintenance of Wakefulness Test (MWT)

The MWT is used to determine a patient's ability to remain awake in the daytime. You'll be asked to schedule an entire day, during which your brain waves, eye movements and muscle activity will be recorded during 20- or 40-minute nap periods scheduled in two-hour increments. Preparations are similar to those for the MSLT. A nighttime test may be scheduled for those whose work schedule requires them to be awake during the night.

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