Adapted from Improve sleepMedical Editor: Lawrence Epstein, MD, Instructor in Medicine, Harvard Medical School.
Snoring may seem like just a nuisance, but it can sometimes indicate a more serious condition called sleep apnea, in which breathing stops and starts repeatedly throughout the night. In simple snoring, the airways remain at least partially open. But in obstructive sleep apnea, the soft tissue of the palate or pharynx completely closes the airway. The brain, sensing a drop in oxygen, sends an emergency message: “Breathe now!” a signal that briefly awakens the sleeper and makes him gasp for air.
In the past, diagnosing sleep apnea always required an overnight stay in a sleep lab. While this remains the gold standard in certain cases, many people can now get tested at home, a more convenient and comfortable option for those with simple symptoms.
Home Sleep Apnea Tests
For people whose symptoms suggest they have moderate to severe sleep apnea and who have no other major medical problems, home sleep monitoring is almost as accurate at detecting apnea as a night in a sleep lab. Home tests are not recommended for people with significant heart, lung, or neurological conditions, or other complex sleep disorders. In those cases, a laboratory study is safer and more accurate.
A big advantage of a home sleep test is its convenience. You sleep in your own bed and take the test according to your schedule. However, you will need to borrow the monitor from a hospital sleep lab and may have to wait a few weeks or more to get it. Home tests are also helpful if your symptoms suggest the need for immediate treatment or if you are bedridden and unable to move. Later after your diagnosis, home tests also provide an easy way for a doctor to check how well your treatment is working.
For an at-home sleep study, you’ll get a small, lightweight monitor, a belt that goes around your midsection, a small finger clip that monitors your oxygen, and an airflow sensor to put under your nose. These sensors and devices measure your oxygen saturation, heart rate and airflow, as well as the movements of your chest and abdomen and your position while you sleep. If you need to get up at night, simply take the equipment with you.
Sleep apnea laboratory tests
If you have additional medical conditions, such as heart, lung, or neurological conditions, a sleep laboratory study is the best option. Sleep lab testing is also recommended if you take opioid medications or have symptoms of other sleep-related problems. A laboratory test is also appropriate if a home test shows that you do not have apnea, but your symptoms strongly suggest that you do.
When you spend the night in a sleep lab, you will wear your own sleep clothes and can bring a pillow from home. The lab usually provides a regular bed in a private room with an attached bathroom. The room is kept as quiet as possible. After a technician installs the sleep monitoring equipment, you’ll be left alone to relax until bedtime.
Throughout the night, lab staff will monitor instruments in a nearby control room. If you need to get up to go to the bathroom, a technician can help you unhook a small box so you can move around easily.
The laboratory tests, known as polysomnography, measure up to 20 different parameters, compared to four in home tests. Small, thin electrodes and other sensors are placed at specific locations on the body to take a variety of readings throughout the night. These locations may include the scalp to track brain waves; under the chin to measure fluctuations in muscle tension (to create a recording called an electromyogram or EMG); near the eyes to measure eye movements; near the nostrils to measure airflow; on the earlobe or finger to measure the amount of oxygen in the blood (using a device called an oximeter); on the chest or back to record heart rate and rhythm; on the legs to record jerks or jerks; and on the muscles of the ribs or around the rib cage and abdomen to control breathing.
The readings are compiled into a single printout (called a polysomnogram) and analyzed by a technician and doctor. If a breathing problem is detected early, you may be awakened and given treatment during the second half of the night. This allows sleep experts to monitor how well the treatment works for you. In rare cases, this process requires two nights.
If disorders other than sleep apnea are suspected, audio and video recordings or additional daytime sleep testing may be performed.
Understanding the results of your sleep study
TwovaluesThey are used to measure the severity of sleep apnea:
- Apnea-hypoxia index (AHI) is the number of times per hour you experience apnea (when you stop breathing completely for 10 seconds or more) or hypopnea (when your breathing is reduced to 30% to 50% below your normal breathing rate).
The AHI value is used to determine the severity of apnea as follows:
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- none or minimum = less than 5
- mild = between 5 and less than 15
- moderate = between 15 and less than 30
- severe = 30 or more
- Oxygen saturation level isthe percentage of oxygen in the blood. A normal blood oxygen level is usually between 96% and 97% for people living at sea level.
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- mild is a reduction between 88% and 90%
- moderate is below 88%
- severe is below 80% and lasts at least 10 minutes
Generally (but not always), the higher your AHI, the lower your oxygen saturation. But there can be a range within different levels of severity. For example, two people with moderate apnea may have very different oxygen drops depending on how long each pause in breathing lasts.
When oxygen saturation levels drop below 80% for 10 minutes or more overnight, it is considered a more urgent case requiring more immediate treatment with positive airway pressure.
It is important to note that people with lung conditions such as COPD tend to have lower than normal oxygen saturation values, sometimes between 80 and 90 degrees. For people with these conditions, the goal of sleep apnea treatment is to restore oxygen saturation levels to their baseline values, not to those of a healthy person without any lung disease.
Sleep studies performed at home and in the laboratory can provide information to diagnose and treat sleep apnea. Home tests offer convenience for people with simple cases, while a sleep lab provides a more detailed evaluation when other health problems are involved. Whichever you choose, getting tested is a crucial first step to better sleep and better health.
