What are the various types of Sleep Studies?

To diagnose sleep-related problems, doctors may use one or more of the following sleep studies:

1. Polysomnogram (pol-e-SOM-no-gram), or PSG
   
2. Multiple sleep latency test, or MSLT
   
3. Maintenance of wakefulness test, or MWT
   
4. Home-based portable monitor (PM)
   
5. Your doctor may use actigraphy if he or she thinks you have a circadian rhythm disorder. 

Polysomnogram

A PSG usually is done while you stay overnight at a sleep center. A PSG records brain activity, eye movements, heart rate, and blood pressure.

A PSG also records the amount of oxygen in your blood, how much air is moving through your nose while you breathe, snoring, and chest movements. The chest movements show whether you're making an effort to breathe.

PSG results are used to help diagnose:

• Sleep-related breathing disorders (such as sleep apnea)
• Narcolepsy (PSG and MSLT results will be reviewed together)
• Sleep-related seizure disorders

Your doctor also may use a PSG to find the right setting for you on a CPAP (continuous positive airway pressure) machine. CPAP is the most common treatment for sleep apnea.

Sleep apnea is a common disorder in which you have one or more pauses in breathing or shallow breaths while you sleep. In obstructive sleep apnea, the airway collapses or is blocked during sleep. A CPAP machine uses mild air pressure to keep your airway open while you sleep.

If your doctor thinks that you have sleep apnea, he or she may schedule a split-night sleep study. During the first half of the night, your sleep is checked without a CPAP machine. This will show whether you have sleep apnea and how severe it is.

If the PSG shows that you have sleep apnea, you may use a CPAP machine during the second half of the split-night study. A technician will help you select a CPAP mask that fits and is comfortable.

While you sleep, the technician will check the amount of oxygen in your blood and whether your airway stays open. He or she will adjust the flow of air through the mask to find the setting that's right for you. This process is called CPAP titration.

In some cases, this isn't done all in the same night. Some people need to go back to the sleep center for the CPAP titration study.

Your doctor may recommend a followup PSG to:

• Adjust your CPAP settings after weight loss or weight gain
• Recheck your sleep if symptoms return despite treatment with CPAP
• Find out how well surgery has worked to correct a sleep-related breathing disorder

Multiple Sleep Latency Test

This daytime sleep study measures how sleepy you are. It's typically done the day after a PSG. You relax in a quiet room for about 30 minutes while a technician checks your brain activity.

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

The types and stages of sleep you have during the day can help your doctor diagnose sleep disorders such as narcolepsy and idiopathic hypersomnia.

An MSLT is repeated four or five times throughout the day. This is because your ability to fall asleep also changes throughout t...