Home Sleep Study
What is it?
A home sleep test is a diagnostic test that can determine whether or not you have obstructive sleep apnea (OSA). It involves the use of a portable-monitoring system that is small enough for you to use at home. The system consists of a small recording device, sensors, belts and related cables and accessories.
The sleep recorder gathers important data as you sleep in your own bed. It receives information from sensors that are applied to strategic locations on your body. For example, sensors near your nose and mouth may measure your airflow. Other sensors around your chest and stomach may measure your breathing effort.
Each sensor sends a signal that is recorded on its own “channel.” Some home sleep tests collect more information than others. A system with a higher number of channels collects more data. A home sleep test can have as few as one or two channels, or as many as seven or more.
In comparison, sleep disorders centers that are accredited by the American Academy of Sleep Medicine record at least 18 channels of information during an overnight sleep study. This also is referred to as a “Type 1” study. An overnight sleep study at an accredited sleep center can detect a wide variety of sleep disorders.
A home sleep test collects less information about your sleep and only detects OSA. It also has a higher risk of error. But for some people a home sleep test may be nearly as effective at detecting OSA as an overnight sleep study.
A Home Sleep Test Will calculate the number of hypopneas and apnea’s that you experience. Partial reductions in breathing are called “hypopneas.” Total pauses in breathing are called “apneas.” In adults each of these events lasts for at least 10 seconds. A home sleep test that measures airflow will calculate the number of hypopneas and apneas that you experience. Having a combined total of 30 or more hypopneas and apneas within two hours indicates that you have OSA.
The best way for a home sleep test to measure airflow is with a combination of these two methods:
Thermal sensors that you place near your nose and mouth. These sensors detect changes in temperature as you breathe in and out. Air that you exhale is warmer than the air that you inhale.
A cannula with a nasal pressure transducer. The cannula is a flexible tube that is inserted into your nose. The nasal pressure transducer is sensitive to minor changes in airflow. But it only measures nasal airflow; it does not measure the flow of air into and out of your mouth.
Home sleep tests often measure breathing effort because OSA involves pauses in breathing that occur even though your body continues making an effort to breathe. In contrast, a pause in breathing with no effort to breathe is a sign of central sleep apnea. The most effective way to measure breathing effort is by a technique called “respiratory inductance plethysmography” (RIP). This involves belts that you wear around your chest and stomach. These belts contain sensors and wires that carry a small electrical current. Chest or stomach movements produce changes in the current.
Blood oxygen level is another common measurement because episodes of OSA may cause a decrease in the level of oxygen in your blood. This level is also known as “blood oxygen saturation.” It is measured using a pulse oximeter on your fingertip.
Who gets it?
A home sleep test is for people who are at risk for OSA. Home sleep tests are not used to detect other sleep disorders.
Key risk factors for OSA include loud and frequent snoring, excessive daytime sleepiness, obesity, hypertension, and witnessed pauses in breathing during sleep. Complete this questionnaire to learn more about the risk factors for OSA.
Even if you are at risk for OSA, your doctor may decide that at overnight sleep study at a sleep disorders center is a better option for you. If you have another major medical problem or sleep disorder, then an overnight sleep study may provide more accurate results. Home sleep tests are not recommended for children.
Your doctor also may use a home sleep test to evaluate your response to some OSA treatments. These include weight loss, oral appliances and surgery.
What happens when I have it?
First you need a full clinical evaluation by a licensed doctor. Your doctor will determine if you are a good candidate for a home sleep test.
Board-certified sleep specialists have expertise and the most experience at evaluating people for OSA. To meet with a board-certified sleep specialist, schedule an appointment at a sleep disorders center that is accredited by the American Academy of Sleep Medicine (AASM). The AASM sets strict standards for centers to maintain. This is to ensure that patients with sleep disorders get the highest-quality medical care. You can find an AASM-accredited center near you by going online to www.sleepcenters.org.?
If your evaluation shows that you are at risk for OSA, then your doctor will schedule you for either an overnight sleep study at a sleep disorders center or a home sleep test. If you are going to do a home sleep test, then you will receive the equipment and instructions that you need. A trained sleep technologist or other health-care professional should either apply the sensors to your body or show you how to self-apply the sensors at home. You should ask any questions you may have about how to operate the recording system. You also should find out when and how you need to return the equipment.
At home you should carefully read any instructions or user manuals that you received with the recording system. Shortly before your normal bedtime, complete the set up of the equipment. Follow the instructions to ensure that the system functions properly. Then get in bed and go to sleep.
At your normal wake time, remove the sensors according to the instructions. Then return the recording system to your doctor’s office.
Who reads it?
The home sleep test records your body’s activity during sleep. It then converts these recordings into visible tracings that can be measured and analyzed. Computer software can help perform some of the basic analysis, or “scoring,” of this data. But automated scoring may be inaccurate.
At sleep centers that are accredited by the American Academy of Sleep Medicine, both a trained sleep technologist and a board-certified sleep specialist will review the data. The technologist will review the computerized scoring. Then he or she will look for any events of abnormal breathing. Finally, the sleep technologist will prepare a summary report for the doctor.
The board-certified sleep specialist will look for signs of OSA. These signs include repeated reductions in airflow despite continued breathing effort, decreases in blood oxygen levels, and arousals. If the information from the home sleep test is adequate, then the sleep specialist will review the results with you.
How do I get the results?
Your doctor will discuss the results of the home sleep test with you. A “positive result” is a strong indication that you have OSA. In this case the doctor will develop a treatment plan for you. It is possible for a home sleep test to produce a “false-positive result.” About 15 percent of people without OSA are likely to receive a false-positive result. This is even more common in older adults who often have other medical problems or sleep disorders that affect sleep. About 30 percent of older adults are likely to receive a false-positive result.
A “negative result” may indicate that you do not have OSA. But home sleep tests can produce a negative result even when you have OSA. This is called a “false negative result.” About 10 percent of people with OSA are likely to receive a false-negative result. This can occur for a variety of reasons. One common cause is data loss. Critical data may be lost if the equipment malfunctions or is set up improperly.
If you get a negative result, then your doctor may schedule you for an overnight sleep study at a sleep disorders center. This study will record more information than the home sleep test. It also will be attended by a trained sleep technologist. He or she will monitor your equipment during the night. The overnight study at the sleep disorders center will show whether or not the home sleep test was accurate.