When it comes to diagnosing sleep apnea, there are several testing options that can be difficult to understand and navigate. Offering clarity on this topic is just one of many covered in detail in the Mayo Clinic Guide to Better Sleep. Learning the pros and cons of at-home versus sleep clinic testing is seen in the following excerpt. Mayo Clinic sleep experts Timothy I. Morgenthaler, M.D., and Bhanu Prakash Kolla, M.B.B.S., M.D., explain how each option works and when an individual should consider getting a sleep clinic test. Many other topics covered in detail throughout the guide include understanding sleep, sleep disorders, sleep medications and others. Help yourself get higher quality sleep by reading the Mayo Clinic Guide to Better Sleep.
Sleep apnea tests: Which one is right for you?
A definitive diagnosis of obstructive sleep apnea can be made only after a sleep test is performed, either at home or in a sleep clinic. Making a diagnosis without a sleep test could result in expensive and burdensome treatment that’s unnecessary and ineffective, or in failure to offer treatment to someone who could benefit from it.
There are two types of sleep tests: one that you perform in your own home and the other that’s done in a sleep lab or clinic. The test done in the clinic is typically called a sleep study, or polysomnography. The type you complete at home is called a home sleep apnea test.
If your doctor believes you may have moderate or severe obstructive sleep apnea with no complications, then a home sleep apnea test may be appropriate. Home tests are far more convenient than those performed in a lab or clinic, and they may yield sufficient high-quality data about your breathing during sleep to make a diagnosis. This is especially helpful in parts of the country where there isn’t a sleep clinic nearby and undergoing a sleep study can be difficult. A home sleep apnea test may even be delivered to you by mail after an in-person or telemedicine visit with a doctor.
Sometimes a home sleep test comes back negative or inconclusive, even in people with a high likelihood of having obstructive sleep apnea. In those cases, doctors will generally recommend an overnight sleep study be performed in a sleep clinic.
An overnight sleep test in a clinic is the appropriate choice for people who have other medical conditions that could be related to obstructive sleep apnea. These include certain cardiovascular and respiratory diseases, opioid use, severe insomnia, a sleep-related breathing disorder called hypoventilation and some neuromuscular conditions. A sleep study might also be appropriate if your doctor is concerned that a home sleep apnea test might not be sensitive enough to make a diagnosis.
Sleep study (polysomnography)
A sleep study consists of many elements. The term polysomnography was coined in the 1970s as sleep scientists bundled together several different diagnostic tests to produce a single exam that creates a full portrait of the brain and body during the night. The study provides a wealth of insights into your breathing, heart rate and rhythm, and sleep stages in the course of the night.
A sleep study is most often used to determine if a person has obstructive sleep apnea or other breathing-related disorders, but it also may be used in the diagnosis of other sleep-related conditions, such as narcolepsy, REM sleep behavior disorder, parasomnias that include sleepwalking or talking, and unexplained long-lasting insomnia.
People undergoing a sleep study often worry if they’ll be able to sleep in a clinic setting. Nearly everyone does fall asleep during the test. Also, sleep specialists are well aware that a night in a sleep lab — attached to sensors and wires as you try to relax in unfamiliar surroundings — will be quite different from sleeping at home. The test, however, doesn’t require a normal night’s sleep. Instead, its primary goal is to gather information about your breathing, brain waves, heart rhythms and movements during sleep. Even short periods of sleep — two hours or more — can reveal much to the specialist evaluating your sleep.
What’s being monitored?
The components that make up a sleep study focus on several aspects of sleep that may be altered by obstructive sleep apnea. During an overnight stay in a sleep clinic, this is commonly what sleep specialists are monitoring:
• Brain waves. They’re recorded with a test known as electroencephalography (EEG). Using sensors placed at multiple points on your scalp, this test monitors the electrical activity in the brain that characterizes the different stages of sleep. Breathing disruptions can upset how your body cycles through stages of light, deep and REM sleep. EEG is a key difference between a sleep study performed in a sleep clinic and a home sleep apnea test. Most home sleep apnea tests don’t measure brain waves and can’t track the stages of sleep and wakefulness precisely.
• Oxygen levels. Oxygen in your blood is measured with a pulse oximeter clipped to your finger. A dip in oxygen levels is one of the most harmful effects of obstructive sleep apnea. A pulse oximeter is painless and uses light beamed through your skin to take measurements and gather data.
• Breathing. It’s measured in multiple ways to reveal different bits of information about apnea episodes. Airflow is measured with pressure sensors at the nostrils. Belts around your chest and stomach measure how much effort is used in breathing, which can help distinguish between obstructive sleep apnea and central sleep apnea.
• Heart rate and rhythm. These are tracked with electrocardiography (ECG or EKG) to detect variability or irregular heart rhythm patterns during sleep.
• Chin muscles. Activity in the muscles is monitored with a test called electromyography, which uses small sensors to measure changes in muscle tone during different stages of sleep, especially REM.
• Leg movements. Sensors placed on your legs measure movement in your lower legs.
• Eye movement. Rapid eye movement (REM) is identified and monitored with small sensors attached to the skin near each eye.
• Body position. Sensors are placed at specific locations on your body to help determine if your breathing disruptions are related to the way you lie in bed.
Home sleep apnea tests
While a sleep study is considered the gold standard for sleep tests, home tests are sufficient for many people. Technological advances have made it possible to gather many of the measurements included in a sleep study at home. A home sleep apnea test generally is less costly and more convenient than a full sleep apnea study conducted in a sleep center. For individuals with signs and symptoms indicating obstructive sleep apnea, this test can accurately identify the condition 90% of the time.
A home test is generally best suited for individuals who may have moderate to severe sleep apnea and whose condition is likely to be uncomplicated, meaning that it isn’t related to another illness, such as cardiovascular disease.
A doctor will generally determine if you qualify for a home test after gathering your medical history and meeting with you — either in person or via a telemedicine visit — to discuss your symptoms and concerns.
Most people prefer the convenience of sleeping in their own bed during the test instead of going to a sleep center. Numerous studies have demonstrated that home tests can effectively diagnose moderate to severe obstructive sleep apnea in individuals who meet certain criteria after meeting with their doctor. In many cases, insurance will cover a sleep study in a sleep center only after a home test has been performed and is inconclusive or raises new questions.
During a home sleep apnea test, an electronic device is attached to your body while you sleep. Home tests are available in different brands and models, vary from one manufacturer to another and may measure different aspects of sleep. As the hardware and software in the devices advance, manufacturers continue to add new features.
Most home sleep apnea tests typically monitor the following:
• Oxygen level. A device placed on your fingertip or ear measures the percentage of oxygen saturation in your blood. Oxygen saturation is a telling sign of how well you are breathing.
• Breathing. Chest movement during breathing is measured via what’s called respiratory inductance plethysmography, which uses elastic bands to measure the expansion and contraction of your chest.
• Blood volume. The amount of blood in tiny arteries is measured with peripheral arterial tonometry (PAT), which can identify breathing disturbances that make the arteries constrict.
• Movement. It can be picked up with a test called actigraphy, which helps determine if you’re asleep or awake.
• Nasal pressure. Some tests monitor nasal pressure by way of a tube fitted with a soft cannula or prongs that is inserted into your nose.
Unlike a sleep study, a home sleep apnea test primarily monitors breathing, not how you cycle through the different sleep stages or how long you’re asleep. Most home sleep apnea tests, therefore, can’t count how many breathing interruptions occurred during total sleep, but instead deliver a number based on breathing interruptions during the test.
Some home tests use pattern recognition to estimate total sleep time and sleep stages. It’s not exactly the same as what’s measured during a sleep study but can provide additional information that may be helpful. When you’ve completed the test, you send it to a laboratory where the data is interpreted and reviewed by a sleep medicine specialist.
An excerpt from Mayo Clinic Guide to Better Sleep by Timothy I. Morgenthaler, M.D., and Bhanu Prakash Kolla, M.B.B.S., M.D.
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