What is polysomnography?
Polysomnography is also known as a sleep study. When a sleep study is performed in a sleep lab, extensive external monitoring is performed during sleep, which would include stickers or leads on the head to monitor sleep, a heart and a respiratory monitor, monitors on the arms and legs to evaluate movements, and a video or audio camera to watch for seizures, sleep walking, and other disturbances. There is a technician who watches these monitors all night and enters the room if one of the monitors becomes disconnected. This is a very thorough test and can evaluate for a multitude of sleep disorders.
What should you bring to a sleep study?
In general, you should pack for your overnight stay as you would if you were coming to a hotel (i.e., comfortable clothing, toiletries, medications, book or laptop, music, et cetera). If you have a particular pillow or blanket which helps you to sleep, you may want to bring this as well. Some people need medications to help them fall asleep. If you think you may need a medication, this should be reviewed with your Sleep Physician at least two weeks prior to your scheduled test date. Medications can affect the test results.
What is an MSLT?
The MSLT or multiple sleep latency test is also referred to as a nap test. It is usually performed after an overnight study. The purpose of the test is to determine the severity of daytime sleepiness and if nighttime sleep (REM) occurs during daytime naps. People are instructed to try and sleep during the naps and are awakened after about twenty minutes for each nap. Up to five naps may be performed, with the test usually ending in the early evening.
What is an MWT?
The MWT is also known as the maintenance of wakefulness tests. During this test, people are placed in their daytime clothing in a darkened, comfortable room and asked to try to stay awake. They are not permitted to perform any activities (i.e., reading, eating, watching television, et cetera). The test usually lasts about 40 minutes.
What is an esophageal pressure study or PTAF?
There is a subset of people with obstructive sleep apnea and daytime sleepiness who have only partial throat closing (not complete obstruction) and their sleep apnea is not identified on a regular polysomnogram. These partial throat closings are called RERA’s, or respiratory-related arousals. Since there is increased airway pressure, but not complete apneas, airway pressure monitors need to be added to the routine polysomnogram to detect this condition.
There are two types of monitors. The first one is called an esophageal pressure monitor. It is a small catheter (tube), a little bigger than spaghetti. The nose is numbed with lidocaine spray, and then this catheter into the nose and down to the back of the throat and remains there during the nighttime sleep study and is removed in the morning.
The second device is a PTAF or pressure transducer to measure airway flow using a nasal pressure thermistor or transducer. The device looks like oxygen tubing or cannula and just sits at the entrance to the nose and measures air pressure and flow. Both devices measure respiratory pressure.
What is an ETCO2?
The ETCO2 or end-tidal carbon dioxide monitor is used to measure how much air is exhaled while someone is sleeping. The more obstructive apnea a person has, the higher the end-tidal carbon dioxide measurement will be. This test has been found most useful in children with apnea. The device to measure this is a cannula worn on the nose, like oxygen cannulas.
What is NPT?
The NPT is a nocturnal penile tumescence test. This test can be performed on men who are undergoing evaluation for fertility or neurovascular disease. It can include a physical monitor and video or photographic evaluation as well. Few sleep centers perform this type of testing. If this type of an evaluation is desired, it is best to start with an evaluation by a Urologist rather than a Sleep Physician.
What is vigilance testing?
Psychomotor vigilance testing or PVT is a measurement of reaction time, or the time it takes someone to respond to an event. An example is how long it takes you to “hit the brakes” on your car when a squirrel runs in front of you. This test is usually performed with a device which flashes a light and the subject presses a button when they see it. Measurements of response time, lack of response or missed responses and incorrect anticipated responses are recorded and compared against standard data. While some driving simulation data (i.e., braking time) may be available, well-established normative data (or normal responses) are not yet fully available. This test does not yet have established standards regarding sleep medicine.
What is a titration study?
Patients with obstructive or central sleep apnea may require an additional sleep study to customize the mask and airway pressure that is needed at night to effectively treat their apnea. If there is not enough