Understanding Polysomnograms - Sleep Studies
What is a Polysomnogram, a Sleep Study, or PSG?
A Polysomnogram (PSG) is a multi-channel recording during sleep. Your doctor, physician or sleep disorder specialist may order polysomnography because of complaints about ailments like daytime fatigue or sleepiness that may be from troubled, problematic and/or interrupted sleep. Polysomnograms are ordered to diagnose, or to rule out, acute obstructive sleep apnea. PSGs can be accomplished during the day or night but most sleep studies are done at night because that's when most people normally have their sleep periods. Shift workers can be accommodated in some labs by having the test at other times - a good lab wants to ensure the testing is done during the patient's normal sleep time and not disrupt the patient's sleep periods.
What to expect during a Sleep Study
Normally the patient comes at a sleep lab in the early evening, and is introduced to the lab environment over a 1 or 2 hour period. Then the patient is "geared" so that multiple channels of data from the brain and body can be recorded after the patient falls asleep. To make the patient more comfortable, Yamhill Valley Pulmonary and Sleep Center is designed in an enviroment that is much like a home would be. A trained sleep technician is always in attendance and is responsible for attaching the electrodes to the patient and monitoring the patient during the study.
Different Types of Sleep Studies
Polysomnogram (overnight study).
A polysomnogram, or PSG, is the most reliable test used to diagnose certain sleep disorders. It measures abnormalities in the sleep cycle. This test can also help to rule out that the person’s symptoms stem from another medical condition. As mentioned above, the test is an overnight study that is very easy to have done; there is virtually little or no discomfort. Electrodes are placed on the skin and scalp. These electrodes are then connected to recording equipment to monitor and record the following body functions during sleep: airflow and respiratory effort, blood oxygen levels, heart rate, electrical activity in the brain, eye movement and muscle movement.
Multiple Sleep Latency Test (daytime study).
A multiple sleep latency test, or MSLT, is conducted, along with a polysomnogram, to confirm or rule out narcolepsy. This test is performed during the daytime and monitors a series of naps to reveal a person’s severity of sleepiness and whether REM sleep (deep sleep during which a person dreams) intrudes inappropriately throughout waking hours. This test is usually done immediately after an overnight study (PSG). You will remain wired with most of the wires from the polysomnogram done the previous night. Typically, a series of five naps are taken at two-hour intervals. The test is usually finished by late afternoon or 5:00pm There is little or no discomfort from the MSLT.
Positive Airway Pressure (PAP) Titration (overnight study).
A Positive Airway Pressure (PAP) titration study is an overnight sleep study that is for treatment rather than diagnosis. When you come in you are tested and fitted for a PAP mask and then hooked up to the polysomnography equipment. During the night the pressure of the air coming from the CPAP or BPAP machine is gradually increased until your breathing is normalized and your correct CPAP or BPAP pressure has been determined. You will be briefly trained that night for proper use and care of your PAP machine and for understanding how it helps you. Once patients become accustomed to the use of a CPAP/BPAP device they typically find a much better night's sleep.
Maintenance of Wakefulness Test (daytime study).
A Maintenance of Wakefulness Test, or MWT, is conducted along with a polysomnogram to determine your level of daytime sleepiness after treatment for narcolepsy or sleep apnea. This test is generally used for commercial drivers, pilots and people who work around heavy equipment to ascertain ability to perform their job safely. This test is normally provided immediately after an overnight study. You will remain wired with most of the wires from the polysomnogram performed the previous night. A series of four “naps” are taken at two-hour intervals. Each nap requires the patient to sit in a chair for 40 minutes and try to remain awake. The test is usually done by late afternoon, or 5:00pm, and there is little or no discomfort for the patient.