For those with snoring issues and/or sleep difficulties, you have probably been recommended to take a sleep test at a sleep clinic. If your family physician has recommended that you take a sleep test, it is very possible that you are showing symptoms of sleep apnea, insomnia, and/or other sleep related disorders. However, what is a sleep test? And what happens at a sleep clinic during this test?
A sleep test or sleep study is also known as a Polysomnography. This test is used by sleep disorder specialists to diagnose sleep disorders, and are done within a hospital or sleep centre. The sleep test records and measures your sleep patterns: brain activity, blood oxygen level, heart rate, breathing, as well as leg and eye movements.
In Ontario, the sleep test is covered under the Ontario Health Insurance Plan (OHIP) and you may do a test every two years. To schedule a sleep test, you will be required to get a referral through your family physician. The test will take place in a private room within a sleep clinic overnight. You will be assigned a single room with a private bathroom. Each room is monitored by the clinic technicians through video cameras, and they can also communicate with you through the room’s audio system. In the case that you require assistance throughout the night, you may alert the technicians through the audio system.
Electrode sensors will be attached to your scalp, temples, chest, and legs with the use of an adhesive; a gel may also be used. The sensor wires will be connected to a computer, but are still long enough for minimal movement. An oximeter clip will be attached to your finger or ear to monitor your blood oxygen level.
How Do I Prepare For a Sleep Test?
As you will be expected to sleep for the duration of the sleep test, it is recommended that you avoid any consumption of alcohol or caffeine throughout the afternoon and evening before the test. You can still have your morning coffee or tea, as long as it does not heavily affect your sleep cycle that night. It is also discouraged to take any naps before your sleep study appointment.
Some–but not all–clinics may offer a shower facility; it is usually suggested by the sleep clinic for you to bathe or shower before you arrive at your appointment. It is also not recommended that you apply any lotions, gels, perfumes/colognes, or makeup before the appointment as these may interfere with the use of the monitoring electrodes.
For comfort, you may bring your bedtime essentials. You may bring some items that you use for your bedtime routine, such as reading materials, as well as wear your sleeping attire. Even if you do not sleep well during the night, it is still possible to get accurate results.
Results from the sleep study will not be available for approximately 3~4 weeks. After the sleep test, you will return home and the sleep clinic will contact you again directly to book a follow-up consultation with a sleep specialist once the results are ready. The information–sleep stages and cycle data–from the sleep test will first be evaluated by a sleep test technician, and then the data would be inputted into a database. The doctor will review the results with you and discuss any diagnosis, treatments, and/or further evaluations that may be required.
The results from the sleep test will provide information in regards to your brain waves and eye movements, which can identify: narcolepsy or REM sleep behaviour disorder; heart rate, breathing rate, and blood oxygen changes that may be caused by sleep apnea; frequent leg movements such as restless leg disorder; and other unusual movements, such as sleep walking.
For those who are diagnosed with sleep apnea after the test, you will usually see certain numbers in accordance to your diagnosis. The most often heard is the measurement called Apnea Hypopnea Index, the AHI. The AHI is the measurement of the amount of apneas or hypopnea events that occur per hour. Simply speaking, it is the amount of times your airways close up per hour during sleep. If the AHI number is recorded to be 5 or higher, you are considered to be suffering from obstructive sleep apnea.
Another measurement linked with the AHI would be the oxygen desaturation index. The ODI measures the average number of desaturation events per hour. Desaturation occurs when the body experiences a decrease in oxygen. It is a measurement linked to sleep apnea as a decrease in oxygen is a sign that you may be suffering from an obstructed airway during sleep.
Through the two above measurements, the sleep specialist can evaluate the level of sleep apnea you may have. The higher the AHI, the more severe the condition. Once diagnosed with sleep apnea, you may be required to take a secondary test with a PAP machine.
For those who are uncomfortable or find it inconvenient to visit a sleep clinic, there are in-home tests available. There are certain clinics or vendors that loan in-home sleep tests for you to use in the comfort of your own home. However, the in-home device can only measure AHI and ODI, and cannot detect any sleep disorder other than sleep apnea. The in-home sleep test is a private test that is not subsidized by the Ontario government nor any private insurance.
The in-home sleep test device is simpler than the devices used in a sleep clinic. In-home devices are generally small machines that are attached to your chest with a strap. Connected from the device are two tubes: one of the tubes go under your nose to measure your breathing, while the other tube is connected to a finger oximeter in order to measure blood oxygen levels. The results will be taken from the machine by the technician and can be processed within a week. Once the results have been processed, you can bring the results to your family physician for evaluation.
If you suspect that you may have sleep apnea or other sleep disorders and/or difficulties, it is best to consult with your family physician to acquire a referral to do an overnight sleep test. The idea of the sleep study may cause you to be nervous but the process will ensure that you sleep safe and sound in the future.