Diagnostic Sleep Study
A sleep study, also known as polysomnography, uses measurements to identify different sleep stages and classify various sleep problems. During the study, the body's activities during sleep (brain waves, muscle movements, eye movements, breathing, snoring, heart rate and leg movements) are monitored by electrodes applied to your head and skin. Flexible elastic belts placed around your chest and abdomen measure breathing. The level of oxygen in your blood and your heart rate are monitored by a clip placed on your index finger or earlobe. As you sleep, you may also be videotaped for review of any unusual movement observed during the study.
What the test does:
This test provides information about the activities of your brain and body systems and throughout the night. A polysomnogram can help:
- Detect sleep-related breathing disorders, such as sleep apnea
- Set the correct levels of continuous positive airway pressure (CPAP) in patients with sleep-related breathing disorders
- Supplement a daytime nap study to see if someone has narcolepsy
- Observe behaviors during sleep that could be violent or harmful to the patient or others
- Provide relief to patients with a history of snoring, high blood pressure, diabetes, obesity, stroke, heart conditions, insomnia and excessive daytime sleepiness
Your doctor will order a sleep study to diagnose a potential sleep disorder or if current treatment has been unsuccessful for a previously diagnosed problem.
Preparing for the test:
The sleep lab where your study will take place is homey and comfortable like a hotel room. The electrodes and wires will be positioned so that they do not interfere with your sleeping comfort. You will be able to roll over and change positions almost as easily as you would in your own bed.
On the day of the sleep study, it is important to avoid caffeine (coffee, tea, cola and chocolate) after 2 p.m., and try not to nap. Before coming to the sleep center, wash and dry your hair, and do not apply hair sprays, oils or gels.
Pack an overnight bag with any essentials you will need. You may wish to include your own pillow and some extra clothing. If you have special needs, advise the sleep center personnel so they can accommodate you.
What to expect during the test:
You will be asked to come to the sleep center in the evening; you will be assigned your own room for the study.
You will not feel any pain during the polysomnogram. Sensors are gently placed on your skin and connected to a computer that receives electrical signals that indicate when you are asleep and awake during the night and monitor your breathing and vitals. The wires are long enough to let you move around and turn over in bed. While the electrodes may feel strange on your skin at first, most people do not find them uncomfortable or an obstacle to falling asleep. The sleep specialist is aware that your sleep at the center may not be exactly like your sleep at home. This is taken into consideration and usually does not interfere with obtaining the necessary information.
The head and face sensors are brainwave and eye-movement detectors that show when you are in REM, or "rapid eye movement," sleep. This is a deep stage of sleep where your eyes roll/move back and forth, and your brain waves are very active. It is also the stage of sleep when you have most of your dreams.
The sensor placed on your neck detects snoring, and the sensors on your chest monitor heart rate and rhythm. The leg sensors show both minor muscle twitches and major movements that occur during the night.
Two respiratory belts and two breathing sensors will also be applied around your chest and abdomen to monitor the amount of effort required for breathing.
Breathing sensors will be placed under your nose to track the number of times you stop breathing. They can also detect low air flow and minor changes in breathing levels.
The sensor placed on your finger, called a pulse-ox, measures the level of oxygen in your blood and any changes in oxygen levels.
The technologists will make sure the sensors are working by performing some bio-calibrations. You will be asked to move your eyes, clench your teeth, do some breathing exercises and move your legs during these calibrations.
You are free to read or watch TV to relax. The lights will then be turned off, and it will be time for you to try to fall asleep. A low-light video camera allows a technologist to observe you. Most people are able to sleep during the study, although often not as well as at home. This will not affect the results of the test. In most cases, a full eight hours of sleep is not necessary for accurate diagnosis.
In the morning, the bio-calibrations will be performed again to test the sensors, and then they will be removed. You can return to normal activities on the day after a sleep study.
What to expect after the test:
A technologist will examine the data from your sleep study, chart your sleep stages and look for any abnormal breathing or leg movement. The results of the sleep study are reviewed by a board-certified sleep doctor. The doctor will review the study to determine the potential for a sleep disorder and, if found, the type of disorder and treatment recommendations. Results of a sleep study will generally be available in about a week.
Your health care provider will contact you to schedule an appointment to discuss your results, and, if you are diagnosed with a sleep disorder, discuss next steps and treatment. Another study may be ordered for therapeutic reasons and as part of your treatment.