Overnight sleep studies are typically thought of as taking place in a hospital or sleep clinic laboratory setting.
However, a few years ago, new technologies made it possible for sleep studies to be take place in patients' homes.
The home sleep study, also known as a home sleep test (HST), has since become a quintessential part of the diagnostic process for identifying one prevalent sleep disorder: obstructive sleep apnea (OSA).
About 75 percent of patients who have been referred to a lab-based sleep study with suspected OSA wind up being appropriate candidates for an HST.
While the HST is not a substitute for the classic overnight attended lab test—it cannot diagnose the majority of sleep disorders—it is now recognized as a good tool to use for people suspected of having OSA but who are otherwise considered healthy.
How does a home sleep test work?
Most HSTs come as a kit with several parts and instructions for how to use them. The most minimal kit will include:
- A small recording device, usually a box
- A nasal cannula (clear tubing inserted into the nostril to measure airflow)
- A belt to wear across the chest to measure the chest's breathing effort
- A pulse oximeter (a finger clip which measures blood oxygen and pulse rate)
Additional devices in an HST kit might include:
- A thermistor (a wire sensor that measures oral breathing)
- A second belt to wear across the lap to measure the diaphragm's breathing effort
- A position sensor to indicate what side you are sleeping on at any given time during the study
- A snoring sensor which measures throat vibrations indicate snoring
Each of these components is applied prior to bedtime; they usually require simple adhesion, but nothing painful.
The recording device, once the test is started, collects a variety of data—how many pauses in breathing occurred, how low the blood oxygen levels dipped throughout the night, any marked changes in heart and respiratory rates.
This data usually provides enough of an objective glimpse into the patient's nighttime breathing patterns to help identify moderate to severe OSA.
Because an HST does not require the overnight attendance of a technologist, it is significantly less expensive. As a result, more insurance payors have elected to reimburse for it; some may even require the less costly HST be used first (for patients who qualify) before an overnight lab study can be referred.
The test has been designed to be simple enough for most patients to use following directions provided by the sleep lab. Some labs offer written directions, while others invite the patient to visit the lab prior to the test to observe a demonstration. The test kit is lightweight and portable and requires fewer components than normally used in a clinical environment.
The HST can be picked up and returned locally. It can also be mailed to patients who live in remote areas, where visiting the sleep lab requires significant travel or expense. Those who have challenges with transportation may also be able to arrange delivery and return of the testing equipment. For many people, the HST may be the only realistic means to determine whether they have OSA. Without easy access, they might never be diagnosed... or treated.
Keep in mind: there aren't enough sleep specialists and facilities to serve the OSA population. One estimate by the American Academy of Sleep Medicine cites only 7,500 board-certified sleep specialists available in the US. With the estimate prevalence of undiagnosed OSA running in the millions, the HST serves as an easier access point for diagnosis and treatment for those who qualify for the home study.
Scheduling is a challenge in our 24-7 world. For many patients, the thought of attending an overnight lab study can wreak havoc on their lifestyles. They may have family members that need supervision at home, for instance. Odd job hours or work-related travel may make it hard to get an appointment any time soon.
Sometimes the comfort level of the patient is also critical; patients with severe anxiety might test better if they are allowed to sleep in their own bed, where all the noises, sights and smells are familiar. First night effect refers to in-lab sleep study results which might be inaccurate because of the patient's inability to sleep normally in a strange environment. The application of the HST can help reduce first night effect.
Patients who are home bound, elderly or require personal assistance might do better with an HST as well.
As with any unattended test situation, things can go wrong. The patient may not apply the sensors correctly. The unit may become disconnected in the middle of the test. Components of the test may fail. A sensor may fall off. In these situations, a second test will need to be conducted.
HSTs do not employ any means for confirming sleep stages. Without knowing how much sleep the patient is actually getting at home, doctors must rely on their feedback about when they slept (or didn't sleep) in conjunction with the data collected by the recorder. Since it's impossible for most patients to accurately note how much they actually slept and when, this leaves it up to the doctor to make an educated guess about the findings.
HSTs tend to underdiagnose OSA. This means that the data collected may show the presence of OSA accurately—which , but if a patient is diagnosed with OSA following an HST, there may still be questions about the best pressure settings for CPAP therapy that the data from the HST may not completely resolve.
Some patients don't qualify
Patients must be screened to qualify for the HST. Many people have other health conditions which make it necessary for them to participate in an attended overnight sleep study in a sleep lab. (We will discuss the conditions of qualifying for HSTs next week... stay tuned.)
What is the procedure for participating in an HST?
Screening must take place before any sleep study referral can take place. Non-sleep physicians typically collect your medical and family history, examine your symptoms, listen to sleep partners' observations and have you fill out questionnaires. Because not all primary care physicians are well versed in sleep training, it is perfectly acceptable for you to ask for a sleep study if you think you might need one.
Typically, your will be referred to a sleep physician at this point, who will review your concerns as well as the records shared by the referring doctor. They will also measure your risk for OSA; if it is likely moderate to severe, and you fit inside qualifying criteria for an HST, you will be referred for the home study.
At a second appointment, you will receive the test and instructions. In some cases, they may even be delivered to you. At that short meeting, you (or your caregiver) will be shown how to apply the components of the test kit, which should take less than 10 minutes. You will also be given you advice for how connect, disconnect, turn on and turn off the recorder. You may even get a chance for hands-on practice.
On the day prior to the evening test, make sure you follow your regular routine, but avoid napping and caffeine after lunch. You may also be asked to temporarily discontinue certain medications by your physician.
On the night of the test, you set yourself up for the test per these instructions, then go to bed as you normally would. In the morning, you turn off the device, disconnect and remove the components and return the kit to the clinic (either in person or by prearranged delivery). You may need to run the test for multiple nights in a row: follow your physician's directions in any case.
The data from the study will be collected, reviewed and scored by a sleep specialist, who will then turn this report over to your physician, who will interpret the results. How long it will take to receive your results depends on how soon you return the device and how soon the sleep physician can interpret the reported data. Usually, HST results do not require more than a couple of extra days to process when compared to traditional overnight lab studies.
Finally, you will be given a treatment plan appropriate to your needs in a follow-up appointment based on your results. They can also connect you with patient support networks at this time and prepare you for regular checkups to ensure your therapy is working for you.
Sometimes, patients discover they still need an in-lab sleep study. It could be that the data from the HST was inconclusive, or that you may not have OSA but the doctor suspects a different sleep disorder.
How can I find out if I qualify for an HST?
Your first step is to meet with your primary care physician and express your concerns about a potential OSA diagnosis. Once they review your information, they will refer to a sleep specialist who will make the final determination.