Polysomnography (PSG) is a non-invasive, painless test commonly known as a sleep study. It is used to diagnose the myriad of sleep disorders by recording your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study over the entire course of the night.
You should avoid any major change in your daytime activities prior to the study. You should also avoid excessive caffeine or alcohol. If you normally use sleep medications, you should bring them to the study, along with any of your other bedtime medications.
When you arrive at the sleep center in the evening for polysomnography, you should be prepared to stay overnight. You may bring items you use for your bedtime routine, and you can sleep in your own nightclothes.
The room where polysomnography is done is similar to a hotel room. It’s is usually both dark and quiet during the test. You don’t share the room with anyone else (unless it is a child study for which a parent is able to stay in a separate bed within the same room). The room has its own bathroom and shower.
The room also has a video camera, so the polysomnography technologists monitoring you can see what’s happening in the room when the lights are out. It also has an audio system, so they can talk to you and hear you from their monitoring area outside the room.
After you get ready for bed, one of the technologists places sensors on your scalp, temples, chest and legs using a mild adhesive, such as glue or tape. The sensors are connected by wires to a computer, but the wires are long enough to let you move normally in bed. A small clip also is placed on your finger or ear to monitor the level of oxygen in your blood.
While you sleep, a technologist monitors your:
All of these measurements are recorded on a continuous computerized graph.
Polysomnography technologists monitor you throughout the night. If you need assistance, you can talk to them through the monitoring equipment. They can come into the room to detach the wires if you need to get up during the night.
In the morning, the sensors are removed, and you may leave the sleep center. You can return to your usual activities after polysomnography. Our staff will call you when the study has been scored and the Sleep Physician can see you for review.
The overnight continuous positive airway pressure (CPAP) titration study involves all the same procedures as done in the overnight polysomnography except with the addition of CPAP. This is a device that consists of a tight-sealing nosepiece through which a gentle stream of air is delivered to enhance your breathing.
You will have the opportunity to trial CPAP at home prior to this study so that you won’t have to adjust to it during the actual titration study. During the night, the technologist will remotely adjust the amount of pressure that the device delivers in order to find that pressure setting that prevents your airway from collapsing. As OSA is made worse while you are sleeping on your back (gravity pushes down on your jaw), the technologist may encourage you to try sleeping in that position at some point during the night.
While CPAP machines are now commonplace, recent advances have introduced Automatic Positive Airway Pressure (APAP) machines. Instead of a continuous fixed pressure, these machines automatically adjust by increasing or decreasing the pressure in response to the amount of resistance it measures in your airway. For individuals who require higher pressures of CPAP (i.e. greater than 10 cmH20) or who show great pressure variability between sleeping on their back versus side sleeping, APAP may be a better choice and improve compliance with therapy at home.
The multiple sleep latency test (MSLT) test is designed to evaluate symptoms of excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet environment during the day. Also known as a daytime nap study, the MSLT is the standard tool used to diagnose narcolepsy and idiopathic hypersomnia.
The MSLT is a full-day test that consists of five scheduled naps separated by two-hour breaks. During each nap trial, you will be asked to lie quietly in bed and try to go to sleep. Once the lights go off, the test will measure how long it takes for you to fall asleep. You will be awakened after sleeping 15 minutes. If you do not fall asleep within 20 minutes, the nap trial will end.
Each nap will be taken in a dark and quiet sleep environment that is intended for your comfort and to isolate any external factors that may affect your ability to fall asleep. A series of sensors will measure whether you are asleep. The sensors also determine your sleep stage.
Excessive daytime sleepiness occurs when you are sleepy when you should be awake and alert. Your sleep medicine physician will recommend an MSLT if they suspect that you have excessive daytime sleepiness related to narcolepsy or a hypersomnia.
The Maintenance of Wakefulness Test (MWT) is used to measure how alert you are during the day. It provides a measure of ability to stay awake for a defined period of time. This is an indicator of how well you are able to function and remain alert in quiet times of inactivity.
The reason for this test is based on the idea that in some situations, e.g. driving, your ability to stay awake may be more important to know in some cases than how fast you fall asleep.
It is a daytime study and you will be given up to 5 opportunities whereby you will be asked to stay awake for 20 minutes while sitting in a comfortable chair located in a darkened, quiet room. Even in this very passive situation with little ambient stimuli, it is expect that you will be able to maintain a level of alertness during the testing period.
