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Generally, a sleep study is a term to describe any test for diagnosing and/or treating sleep problems.

These include the portable or home sleep test (HSAT), the nocturnal polysomnogram (NPSG), the split night study, the PAP titration, and daytime studies that include the Maintenance of Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT).

What are the main sleep tests or studies?

There is more than one kind of sleep test. You cannot assume that the one your doctor orders for you will be the same one ordered for a friend or relative. Often, it’s the patient’s insurance carrier which has a shaping influence over sleep testing protocols, as well.

Home Sleep Apnea Test

A home sleep test (HSAT) is typically prescribed when your doctor suspects you might have a sleep breathing disorder. You will be sent home to sleep that night with a kit composed of various sensors, which usually include:

  • a belt to measure respiratory “effort”
  • a finger probe to measure heart rate and blood oxygen levels
  • a cannula sensor used to measure airflow

When you pick up the test, your doctor or sleep technologist should show you how everything is attached and how the test is turned on and off. There should also be written and/or video instructions contained with the test kit, in case you forget.

The HSAT is often required by insurance payers to screen patients for the likelihood of sleep apnea before they come in for an overnight test as the HSAT is considerably less expensive.

The test is fairly simple and mostly accurate enough for the purposes of detecting the presence of sleep disordered breathing.

It is also, for some patients, a more desirable option as it is conducted in the privacy and comfort of the patient’s home.

In October 2017, the curator of SHC will post a video demonstrating how to perform a home sleep test to show just how easy it is. Stay tuned!

Generally you return your HSAT hardware on the morning after the test and follow up within a week with your sleep physician to discuss results.

An HSAT may not work the first time, and you may be asked to do the test again. You will not be charged for any tests in the case of a hardware failure.


Sometimes the results of an HSAT will indicate that you need to go in for an overnight sleep study in the sleep clinic because the results were either:

a/inconclusive, but strongly suggestive of a sleep disorder

b/conclusive (a sleep disorder is or isn’t present)

Inconclusive testing means there’s a likelihood that additional tests may be needed to uncover a different sleep problem, or the results were borderline for a sleep breathing disorder.

Conclusive outcomes may still require further studies to identify appropriate therapy settings before treatment can be started.

If you are diagnosed with sleep apnea based on an HSAT, you will meet with a durable medical equipment (DME) provider to receive your sleep apnea treatment. This is usually an automatic positive airway pressure (Auto-PAP) machine which comes with a preset pressure range.

When HSAT test results are negative for sleep disordered breathing, this doesn’t necessarily mean the patient doesn’t have a sleep disorder. Many other sleep disorders besides sleep apnea can cause excessive daytime sleepiness or sleeplessness at night, so a followup study in a lab setting may still be required.

Nocturnal polysomnogram

A nocturnal polysomnogram (or NPSG) is a diagnostic test conducted in a sleep laboratory which measures physiological data occurring in patients while they sleep.

The data come from various kinds of sensors attached to different parts of the body: the scalp, the chin, the brow and cheek, the throat, the nose and mouth, the legs, the chest, and the abdomen.

About the sensors

  • Sensors on the scalp measure changes in brain wave (EEG) architecture, which show changes in sleep stages. These can also capture unusual brainwave activity that might be related to seizure disorders or epilepsy.
  • Chin sensors (EMG) indicate when patients are awake, tense, lightly asleep, or in REM sleep.
  • Brow and cheek sensors record different kinds of eye movements (EOG) during both sleep and wake stages.
  • The throat sensor records snoring activity.
  • The nose and mouth sensors measure incoming and outgoing airflow.
  • Leg sensors (EMG) indicate muscle activity in the limbs that can be caused by arousals, movement disorders, and other physiological disturbances.
  • Electrode patches on the chest record ECG patterns (heart rhythms), and belts around the chest and waist show evidence of respiratory effort (or lack thereof), which helps to identify breathing disorders of sleep.
  • An additional device, the pulse oximeter, is clipped to the patient’s fingertip; this device measures both the heart rate and the amount of oxygen saturating the blood, which lets the interpreting physician know just how much (or how little) oxygen a patient is circulating while they sleep.

Once the patient is hooked up to these sensors, they are asked to sleep in a technologically equipped bedroom and monitored via video and audio equipment for the night.

The laboratory technologist collects data which, when scored and interpreted by a sleep physician, can provide answers to explain certain kinds of health concerns, such as excessive daytime sleepiness, morning headaches, low blood oxygen at night, or high blood pressure.

Generally these tests are administered during the evening. However, some patients who work overnight shifts may be scheduled for attended polysomnograhy during the day, when they typically sleep.

Split night study

This test is performed for some patients for whom a diagnosis of Obstructive Sleep Apnea (OSA) or upper airway resistance is highly likely. This is often determined by a pulmonologist who specializes in heart and lung disorders.

A split night study starts out like the NPSG; the patient is prepared in the same way and the same signals are attended during the test. However, respiratory events are a chief focus of observation in this test.

Respiratory events are moments during sleep when the airway is partially or completely obstructed for at least ten seconds, or when arousals occur due to airway resistance, such as in the case of heavy snoring.

Respiratory events in a split night study are tallied over the first third of the test and, if the patient has experienced enough to meet lab protocol, they are given positive airway pressure (PAP) therapy to help eliminate these events.

PAP Titration

This study involves the use of a positive airway pressure device and mask to identify the best therapeutic measurement of air pressure for people with OSA.

Positive airway pressure is essentially delivery of very light puffs of air to the patient’s upper airway in order to assist the patient in completing inhalation and exhalation, both which may be obstructed due to confirmed issues of blockage in the upper airway.

The patient is acclimated to the mask by wearing it before the titration using very light pressure. Then they are hooked up like they would be in an NPSG. However, in the case of a PAP titration, they start their study using PAP therapy.

As they sleep, the technologist remotely and digitally adjusts the therapeutic level of positive pressure feeding through the device and mask, as well as humidity and pressure support for exhalation, until they determine the pressure which most benefits the patient is the most comfortable for them.

Maintenance of Sleep Latency Test

This test helps to identify hypersomnia condition, such as Idiopathic Hypersomnia, Narcolepsy with or without Cataplexy, and Klein-Levin Syndrome (“Sleeping Beauty” disorder).

The MSLT is usually performed on patients on the morning following an NPSG. These are people who are known to be excessively sleepy during the day but who have been determined not to have sleep apnea.

Some of their overnight sensors are removed while others are left on for up to 5 tests performed about 2 hours apart during the day. These nap periods allow the technologist to record their brain wave patterns at those times, which can reveal conditions of hypersomnia.

Maintenance of Wakefulness Test

This test is often used for commercial truck drivers, airline pilots, bus drivers, and other operators of public or commercial vehicles or industrial equipment—anyone who may be at risk for falling asleep at the wheel or while operating machinery.

For these workers, the risk of drowsy driving is too great to ignore any problems with untreated sleep disorders, especially sleep apnea, which can be more common among this population.

A patient undergoes an MWT by being hooked up to specific set of sensors, then sitting in a dark room for a certain period of time during the day. This objectively determines how well they can stay awake in low stimulus conditions.

Will insurance cover my sleep study?

Generally, sleep studies are considered medically necessary because they are critical to identifying underlying sleep disorders, especially those related to disordered breathing.

Fortunately, most sleep disorders are treatable and therapies are also generally covered by most insurance companies.

Different insurance companies cover different kinds of tests and durable medical equipment (DME) related to sleep testing, so it’s best to consult your insurance company to see what they will reimburse. (Your doctor should also be able to help you with this.)

You will likely need to be referred for a test and might need to have your studies and equipment pre-approved by your insurance company before taking a test. Often a doctor’s choices for treatment will be limited by what your insurance is willing to reimburse.

It is advised that all patients look at their insurer’s policies regarding failed or incomplete tests. Generally, patients aren’t charged for tests that have failed mechanically.

If you decide in the middle of a test that you no longer want to participate

If a patient leaves a study in progress, this is considered “against medical advice” (AMA). You will need to sign a form (called an AMA) stating you understand you are leaving against medical advice.

Your insurance company may or may not reimburse in this case, and you could be held responsible for paymentpartially or completelyfor this expensive test.

How do I prepare for a sleep study before I get to the lab?

Usually the lab will give you specific instructions, so please consult them first. In their absence, here are some general guidelines.

To Do List for a Sleep Study

  • Shower
  • Come in with clean, dry hair
  • Remove makeup
  • Eat your evening meal 2 or more hours before coming to the lab
  • Remove dark nail polish, if possible, as it might interfere with function of the finger probe
  • Avoid alcoholic or caffeinated beverages or foods 5 or more hours before coming to the lab
  • Prepare to be told you cannot smoke at least 30 minutes before your study starts (which includes vaping)
  • Take your usual medications, but do not take any sleep aids until you’ve alerted your technologist to the fact you are taking them; it is important to start your study awake!
  • Manage your diabetes medications as usual
  • Expect to start your sleep study with all electronics—including the TV, cellphone, and radio—turned off, even if it’s normal for you to have these on at bedtime

Packing List for a Sleep Study

  • Clothes to sleep in (do not bring lingerie); pajamas, nightshirts, t-shirts, and shorts are all acceptable. Nude sleeping is not permitted in the sleep lab and hospital gowns may or may not be available
  • Slippers to walk in, and a robe; some labs will set up patients in their rooms, while others will set them up in separate locations inside the lab where other patients might see them
  • Comfort items like a favorite pillow, blanket, or stuffed animal
  • Your evening medications (note: technologists are not permitted to administer medications). These could include your usual prescriptions as well as over-the-counter pain relievers, decongestants, nose sprays, antacids, heartburn medications, and the like
  • A white noise machine, if this is helpful for you (some labs have these available)
  • Your usual personal care items like shampoo, conditioner, soap, toothpaste, toothbrush, deodorant, etc. Though many sleep labs are set up to resemble hotel rooms, they are still medical facilities and do not always provide these personal care items
  • If you are diabetic, having some snacks on hand is okay if that will help you regulate your blood sugar through the night
  • Most labs have overhead or standing fans to help keep rooms cool for patients who need them

List of Things NOT TO DO OR PACK for my sleep study

  • Anything with a strong fragrance; most labs are fragrance-free environments
  • Fast food or other carry-out food items that have a strong aroma
  • Pets (service animals are an exception)
  • Loved ones may come with you to the lab to help you get comfortable, but they cannot typically stay the night unless they are pre-approved as caregivers; patients under the age of 18 must be accompanied by a parent or guardian who will be expected to stay overnight
  • Electronics like laptops, cell phones, and handheld gaming devices; if you do bring them with you, please be prepared to turn them off completely stash them for the night. Electronics can cause problems with sleep onset as well as disrupt electrical signal data collection
  • Alarm clocks; you will be woken by the technologist in the morning upon completion of the study
  • Jewelry can interfere with electrical signal data collection and is best left at home

What medications can I take before my sleep study?

Unless advised differently by your physician, take your normal medications.

If you have sleeping pills, hold off taking them until you have had a discussion with your technologist, as they will direct you to the proper time to take them.

If you have problems with heartburn or pain or congestion, you will be allowed to take medications for these as necessary to help you get to sleep comfortably.

However, the lab will not necessarily have these on hand, and sleep technologists are not nurses, so they cannot legally dispense medication of any kind, even aspirin or antacids, so please make sure and bring your favorites in case you need them.

How will the technologist prepare me for a sleep study once I’m at the lab?

Depending upon the nature of your visit, the technologist will prepare you for your study in various ways.

Typically, preparation will include application of scalp and body sensors and trying out several kinds of PAP masks to find the one that fits you best and is most comfortable for you, in the event you will need it.

The technologist is also a sleep educator who is trained to answer all your questions about the test, so feel free to ask questions of them or express any fears or concerns you may have.

At “Lights Out,” the study begins, and your sleep technologist will work with you to perform calibrations. These include little exercises you complete at their instruction, such as blinking your eyes or pointing your toes, so they can capture a digital record of the baseline measurements related to each of the sensors you have attached to your scalp and body.

Each patient displays different variations on these signals (size, shape, speed), so these calibrations come in very handy for the scoring technologist and physician later when they prepare to score and interpret your study after you’ve gone home.

Why do the technologists have to audio and video record my study?

Often the sensors attached to the patient show unusual signals. Using video and audio feeds live helps the technologist to determine whether the unusual signals are due to sensor malfunction or to symptoms caused by sleep disorders or harmless patient movements.

Some kinds of sleep disorders, those involving unusual movement or vocalization, require audio-visual records to confirm diagnostically.

Audio-video streaming also helps the sleep technologist and patient to best communicate with each other as they are in separate spaces for most of the test.

Physicians who have questions about certain aspects of the study may call up both the audio and video recordings to see what happened in those moments during the study, long after the study has been completed.

Finally, because of the somewhat intimate nature of the sleep test, an audio-video recording offers both the patient and the technologist legal protection against any misunderstandings which might occur while the technologist is in the room with the patient at night.

Conversations and activities are recorded in order to provide some objective data when such disagreements arise in these rare occasions.


Snoring, catathrenia, and sleep talking can be confirmed through audio feed.


Generally, the image of the patient, which is black and white, is kept in a small window inside the upper corner of the computer monitor screen in the lab. The technologist will refer to it to examine and corroborate patterns coming from the signals without having to disturb the patient.

Body position, an important part of data collection, can be confirmed via video feed. So can unusual movements that may indicate rare sleep disorders.

What happens if I have trouble sleeping during my sleep study? Won’t it ruin my test?

Most patients are expected to be a little on edge at first; this is normal. Your best approach is to try to sleep as well as you can and try not to worry about your sleep quality or quantity. The vast majority of sleep study patients do, in fact, sleep enough during a study to provide meaningful results.

It may help to know that the technologist runs the study in such a way as to account for so-called “first night effect,” which impacts nervous patients who can’t sleep initially. Very rarely does anxiety at the beginning of the night impact the overall efficacy of the test.

What are the technologists doing while I’m asleep?

They are not sleeping! They are, in fact, extremely busy, especially if they have multiple patients. They:

  • monitor the data collected by the signals attached to your scalp and body
  • write regular reports and tag specific data inside the study as it happens so the scoring technologist and physician can interpret the study later
  • adjust PAP pressures and settings or oxygen settings, as needed
  • fix or replace any sensors that might have fallen off or might otherwise not be working properly in order to collect the clearest data
  • assist you with getting to the bathroom in the middle of the night
  • help you with comfort issues (more pillows, cooling fans, noise machines)
  • update medical records related to your study
  • prepare your followup paperwork

What time will I get up? 

Generally speaking, patients are woken up by the technologist between 5 and 6am.

Following “Lights On,” they will calibrate your signals, unhook you from all the sensors, go over your followup paperwork with you, and offer any assistance you need in getting ready in the morning.

This usually takes less than 30 minutes, after which you are free to clean up.

Some labs offer breakfast foods; hospital-based labs often hand out coupons for free breakfast in the cafeteria.

Please don’t linger

The technologist you have worked with at the beginning of your study will most likely be the same technologist who will unhook you.

At the end of your test, they will be busy cleaning and sterilizing equipment, assembling packets of information for you to take home, updating medical records, and preparing your data for scoring by another tech. In some labs, they are also tasked with changing linens and towels and restocking the bedrooms and bathrooms.

Sleep lab techs generally work 12-13 hours overnight, then go home, sleep during the day, and return to work the next night.

As a courtesy, it is helpful as a patient to not linger after your study is completed and you have cleaned up.

If you are waiting for a ride, it is better to do so in the waiting room so the technologist can complete their shift. They are unable to leave until their patients have vacated the lab or someone else has arrived to relieve them, which may or may not correspond with the end of their shift.

How soon will I find out my sleep study results?

Most labs will get back to you within 2 weeks. Your sleep technologist should give you information about the process following your study before you leave the lab.

Note: Technologists are not physicians and are, therefore, not qualified to diagnose patients. The technologist cannot discuss your test results the following morning, as a typical test includes about 800 pages of raw data that still require scoring before the physician can interpret the results.

If you have any concerns, your technologist can take notes which can be forwarded on to your physician with your study.

Will I have to have more than one sleep study?

It depends upon what your particular sleep issues are. Some sleep disorders are adequately diagnosed after a single study, while other sleep disorders require different tests on different nights and sometimes even during the day to get at the root cause of the problems.

There is no typical procedure; each test for each patient is determined by their unique needs.


5 Comments on SLEEP STUDIES

  1. Simply my vision for what sleep testing should become:
    In the future I imagine that you will start your sleep testing process with an on line class. You will read an article or two about the equipment you will be using with emphasis on how to put it on, confirm that it is working properly, take it off, and care for it over the week or two that you will be using it. Then you will view several videos and use some interactive learning tools to get a real handle on what is going on as much as possible from the web. There will be some on line testing and when you pass the tests you are ready for the next phase.
    Then you are off to a class. With the help of the instructor you will indeed put on the equipment while the instructor makes sure that everything has proper placement and comfort. When the instructor is satisfied that you are able to use the equipment well you are certified and given the sleep testing equipment to take home.
    Each night as you use the equipment when you do believe you have put it on properly you will punch a button on the equipment. This will notify a technician at the data gathering station that they need to look at your data coming in and see that everything is functioning properly. If so they punch button and a green light goes on letting you know that the test is beginning. You then go to bed.
    The test will be for much more than one night but if sleep disordered breathing is discovered you will be shipped the proper CPAP machine (which you will have been already trained to use) and will begin a months long titration process. Indeed monitoring your own data and making guided decisions about changes in the way the machine functions to meet your needs will be ongoing as it must be.

  2. I've never had a problem wearing CPAP and it keeping me awake. Once I was on it I lost something like 20 lbs in the first 2 months of using it. I have several sleep disorders, including Idiopathic Hypersomnia, so I can't say that CPAP completely cured me- that was never the goal. But it did make my sleepiness more tolerable and it did what it was intended it do. CPAP does not cure you overnight, they take time to adjust to, and the more research you do on the benefits the better. I've had 3 PSGs and have never had any problem sleeping. Your attitude going in matters. If you think the sleep study is a waste of time or that you're going to “fail” then that will affect your sleep. PSG's are the gold standard for a reason. There are some disorders that don't show up on PSG's- but you still need to have a PSG to rule out those disorders.

  3. Unknown:

    You are describing patient education. I'm all for it! And while it doesn't happen exactly the way you describe it, it's already happening in terms of teaching patients how to use their equipment and so forth. But it can only happen after a diagnosis of sleep apnea has been determined. CPAP doesn't treat dozens of other sleep disorders.

    Patient education is a very careful balance of giving the patient the right amount of education at the right time. I'm not sure the extensive training you describe would work in a real world situation because of so many other factors that sleep labs have no control over. And don't forget, there are patients who don't want to succeed at CPAP because they don't believe they need it and don't want it to begin with. In those cases no amount of education is going to change their attitude (as Kasha points out).

    You also describe remote data collection, which is already happening. This is how the lab knows when a patient is compliant with their therapy. We can't rely on patients telling the truth and insurance pretty much requires verifiable proof of adherence before they will reimburse.

    However, there's a big flaw in your description of a future sleep test: what you are describing is a CPAP titration versus a diagnostic test, if I'm reading this correctly, and the challenge with this is that you are assuming that every single sleep study will be a CPAP titration, when in reality, some people have sleep studies to discern whether they even have a sleep breathing disorder. Many patients have other sleeping disorders which don't have anything to do with apnea and they must have an overnight test to determine what their issues are. Again, the test provides the only verifiable evidence that insurance will accept when it determines its reimbursement.

  4. My vision for the sleep test of the future would simply take the equipment developed to get the real in the home data and make it available for clinical use. It is a total redesign of the equipment such that it can be self applied and used in the home by the person without the need for some stranger to come into the home. We really do need data which is gathered in a truly scientific manner not in a manner which obviously changes the characteristics of the subject being measured. As I have mentioned before the current in lab polysomnogram is simply very bad science.

  5. I dont have sleep apnea I have upper airway resistance and cpap has changed the quality of my life dramatically in less than 6months ….my brain fog has reduced my body aches are minimal I no longer spend all my days sleeping I have returned to work we have 4 cpap users in our home and I truely believe that encouragment and education has been the key to sucessful treatment for us all

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