Adapted from
Improving sleepMedical Editor: Lawrence Epstein, MDinstructor in medicine, Harvard Medical School.
Snoring may seem like just a nuisance, but sometimes it can signal a more serious condition called sleep apnea where breathing repeatedly stops and starts during the night. In simple snoring, the airways remain at least partially open. But in obstructive sleep apnea, the soft tissue in the palate or pharynx completely closes the airways. The brain, sensing a drop in oxygen, sends an emergency “Breathe now!” signal that briefly awakens the sleeper and causes them to gasp for air.
In the past, diagnosing sleep apnea always required an overnight stay in a sleep lab. While this is still the gold standard in certain cases, many people may now be tested at home – a more convenient and comfortable option for those with straightforward symptoms.
Sleep apnea test at home
For people whose symptoms suggest they have moderate to severe sleep apnea and who have no other significant medical problems, home sleep monitoring is nearly as accurate in detecting apnea as a night in a sleep lab. Home testing is not recommended for people with significant heart, lung or neurological conditions or other complex sleep disorders. In these cases, a laboratory test is safer and more accurate.
A big advantage of a home sleep test is its convenience. You sleep in your own bed and you do 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 receive it. Home tests are also useful if your symptoms indicate a need for immediate treatment or if you are bedridden and unable to move. Later, after your diagnosis, home-based tests also provide an easy way for a doctor to check how well your treatment is working.
For a home sleep study, you get a small, lightweight monitor, a belt you put around your midsection, a small finger clip that monitors your oxygen, and an airflow sensor to place 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 have to get up at night, you just take the equipment with you.
Laboratory studies of sleep apnea
If you have additional medical conditions such as heart, lung or neurological conditions, a laboratory test is the best choice. Sleep lab testing is also recommended if you are taking opioid medications or if you have symptoms of other sleep-related problems. A lab 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 laboratory, you wear your own nightwear and you can bring a pillow from home. The laboratory usually provides a regular bed in a private room with an attached bathroom. The room is kept as quiet as possible. After a technician sets up the sleep monitoring equipment, you are left alone to relax until bedtime.
Throughout the night, laboratory staff will monitor the instruments in a nearby control room. If you have to get up to use the toilet, a technician can help you unhook a small box so you can move around easily.
Laboratory tests, known as polysomnography, measure up to 20 different parameters compared to four in home-based tests. Small, wafer-thin electrodes and other sensors are placed on specific body sites to take a series of readings throughout the night. These places can include on your scalp to track brain waves; under your chin to measure fluctuations in muscle tension (to create a recording called an electromyogram, or EMG); near your eyes to measure eye movements; near your nostrils to measure airflow; on your earlobe or finger to measure the amount of oxygen in your blood (using a device called an oximeter); on the chest or back to record pulse and rhythm; on your legs to record jerks or jerks; and over your ribcage muscles or around your ribcage and abdomen to monitor breathing.
Readings are collected on a single printout (called a polysomnogram) and analyzed by a technician and a doctor. If a breathing problem is detected early, you may be awakened and treated in the second half of the night. This allows the sleep experts to monitor how well the treatment is working 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 tests may be performed.
Understand the results of your sleep studies
Thawvaluesused 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 longer) or hypopnea (when your breathing is reduced by 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 minimal = less than 5
- mild = between 5 and less than 15
- moderate = between 15 and less than 30
- difficult = 30 or more
- Oxygen saturation level isthe percentage of oxygen in your 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 to between 88% and 90%
- moderate is below 88%
- difficult is below 80% lasts for 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 difficulty. For example, two people with moderate apnea may have very different oxygen dips depending on how long each pause in breathing lasts.
When the oxygen saturation level falls below 80% for 10 minutes or longer during the night, it is considered a more urgent case requiring more immediate treatment with positive airway pressure.
It is important to note that people with lung diseases such as COPD tend to have lower oxygen saturation values than normal, sometimes in the high 80s to low 90s. For people with these conditions, the goal of treating sleep apnea is to restore oxygen saturation levels to their baseline values, not to those of an otherwise healthy person without any lung disease.
Home-based and laboratory-based sleep studies can provide information to diagnose and treat sleep apnea. Home testing offers convenience for people with straightforward cases, while a sleep lab provides a more detailed evaluation when other health issues are involved. Whatever you choose, getting tested is a crucial first step towards better sleep – and better health.
