What happens at an overnight sleep study?

No need to fear the unknown at your sleep study!

Patients who prepare carefully for a sleep study can expect to have a more positive and comfortable experience overall.

Previously in Sleep Studies Demystified: Are you prepared for your overnight sleep study?

What exactly happens when you have an overnight, in-lab sleep study? Many patients arrive at the sleep clinic with very little understanding of what they should expect. It’s not a typical diagnostic procedure, after all.

Patients may be at the lab or clinic for close to 12 hours, where they will encounter a “hookup” and be asked to sleep under surveillance.

If you’re anxious about what will happen to you at your sleep study, read on. This post endeavors to demystify what a sleep study is by explaining why the hookup is important and what you can expect while you are there.

To be clear, this blog post refers to overnight, in-lab sleep studies (polysomnography), not to the HSAT, or home sleep apnea test, which takes place in your own bedroom.

Sleep study: Upon arrival

What may be familiar

This will probably feel, in some ways, the most familiar to you. A sleep technologist will place you in a sleep suite, ask you some questions, collect paperwork, and take vital signs.

Keep in mind: sleep technologists are not nurses. They are trained specifically to conduct sleep studies. They work in concert with a physician to ensure you receive an accurate diagnosis, proper treatment, therapy management, and sleep health education.

Sleep techs do not have the same training as nurses. For instance, if you need a medication, even something as simple as an aspirin, the sleep technologist cannot provide this for you; it is not legally within their bounds to do so.

Without nursing training, sleep technologists also cannot provide toileting assistance or other nursing skills. If you need caregiver support during the night, you will need to bring along that person to perform these duties. Most sleep labs have additional bed space set aside for caregivers.

What may be unfamiliar

What might be more atypical is that when you arrive, your testing room will not resemble a typical exam room in a hospital or clinic. Instead, it will look more like a hotel room, with a large bed, room darkening shades, and its own bathroom (in most cases).

The diagnostic equipment in the room may or may not be fully apparent, but this is by design. The sleep physician wants you to have the most comfortable experience possible so that you will sleep well enough for the technologists to collect adequate data for your test.

One more thing: If you sleep physician suspects you have sleep apnea, you will be asked to try on some different masks you may need to wear for at least part of your study. The goal is for you to get a sense of what it feels like to wear one and to find the one that fits you the best.

If you ultimately need to use positive airway pressure (PAP) therapy following a sleep apnea diagnosis, you will have ample time to address mask styles and fittings at that time.

Also worth noting: If you normally take medications at bedtime, or have been prescribed a sleep aid, please let your sleep tech know. They will tell you when the time is right to take these medications. It can be problematic for your study to take certain medications too early into the procedure.

Sleep study: The hookup

A typical overnight sleep study in the lab requires data be collected of the following: heart rate, brain activity, oxygen levels, eye movements, airflow, respiratory effort, body movement, snoring, and more.

The “hookup” is essentially the time when the sleep technologist affixes sensors to your body in order to provide this data collection, using a sophisticated digital diagnostic system. This aspect of the sleep test can take up to an hour.

Keep in mind: Often, a sleep technologist will be running two, maybe even three, sleep studies at once. They cannot be in all three rooms simultaneously, so you should expect a short period of waiting between your hookup and “Lights Out” (the start of the test) as a result.

This time is best used by relaxing. Reading a book, knitting, or other calming activities are recommended. Some labs have televisions to help you get ready for bed, but some channels, such as news channels or high-octane movie channels, may be blocked.

This is also by design: certain kinds of media (including social media) can be stimulating, which may make it harder to fall asleep.

Sleep study: The wires

The sleep technologist applies numerous sensors on your body in order to record data that will help the sleep physician arrive at a sleep disorder diagnosis (if you have one).

The sleep test itself is formally known as the polysomnogram. It records at least 12 channels, which require at least 22 sleep study wires to be attached to you. Each sleep clinic will vary in the number of channels it uses, but the number used typically follows your physician’s request.

Here’s how it typically breaks down:

  • Three or more channels are used to measure brain activity (EEG)
  • Two to three monitor chin muscle tone (EMG)
  • One or two capture airflow data (cannula and nasal pressure transducer) and snoring (snore microphone)
  • Eye movements are recorded using two sensors (EOG)
  • Each leg will receive two sensors to quantify movements (EMG)
  • There’s a sensor that reads your blood oxygen saturation levels (pulse oximetry) and three electrodes to trace your heart rhythm and rate (EKG)
  • Finally, you will wear two belts which document movements along both the abdomen and chest wall (piezoelectric sensors), coupled with a position sensor to show what side you are sleeping on.

Of special importance

While none of these sensors is considered optional, some of them has special significance to the study.

For instance, the EEG is how the technologist and physician can identify sleep stages, phases, and architecture. These electrodes are attached to your scalp along the top, back and forehead areas.

Eye movements during sleep are important for tracing periods of rapid-eye movement (REM) sleep.

It may seem unimportant, but knowing body position can be very useful for identifying specific kinds of sleep disorders. Sometimes, sleep apnea only happens during REM sleep, for instance, and knowing this informs the doctor’s decision about treatment.

Finally, while it may seem creepy that there is audio-visual equipment in your sleep suite, the use of these aids in a number of ways.

First, AV surveillance helps the technologist verify body position.

It also assists in documenting possible movement disorders or seizure activity.

Finally, recordings of the entire study are helpful for both the patient and the sleep technologist in the event something unexpected takes place, such as a heart attack or accusations of improper behavior.

Sleep study: The hookup process

You will be asked to put on your sleeping attire, then the sleep technologist will use hypoallergenic tapes, creams, and gels to apply these sensors to your body.

They may elicit your help in placing some sensors beneath your clothing and, in some cases, they may shave a small patch of hair on the chest or legs to ensure the sensors can deliver unimpeded signal data.

The electrodes that are placed on the head have colored wires to help the sleep technologist keep track of which have gone where. It’s in your best interest to resist touching, moving, or removing these wires during the entire course of the study.

If a wire comes detached during your study, the sleep technologist will know because of a change in the signal recorded in the lab and will take care of repositioning or replacing these.

The head wires are typically collected and ponytailed to the back of the head so that they can be lifted out of the way so you can sleep comfortably.

Each wire is connected to a designated spot in a jackbox you will carry with you while you are awake, which will often be positioned in a special holder away from your bed so as not to disturb you or the study.

You may feel like you are covered with electronics! But ultimately (and I can say this, as I’ve had 3 sleep studies myself), they are fairly inconspicuous and shouldn’t intrude on your sleep. You’ll still be able to move around, turn over in bed, and find a comfortable position.

Sleep study: “Lights Out”

Your sleep study ultimately begins when the sleep technologist turns out the lights in your sleep suite and shuts the door.

Then they will go to the lab and run some calibrations to confirm all the sensors are working as expected. If they aren’t, they will return to your room then (and at any time during the night) to correct sensor placement.

Once all the sensors are confirmed in place, the sleep technologist will speak to you through the intercom and ask you to perform a brief series of simple activities, such as looking up and down and taking deep breaths. Once this concludes, your study is live and all you need to do is fall asleep.

Don’t worry about how long it takes to fall asleep, or whether you will sleep enough. The vast majority of sleep lab patients provide more than adequate data to arrive at a diagnosis even when they don’t sleep as well as they do normally.

During the night, you will be able to ask for help if you need it. Simply speak out loud. The sleep technologist will hear your voice and respond.

Help includes getting up to go to the bathroom (the sleep technologist will “unhook” you from the jackbox so you can move freely and independently to and from the bathroom), retrieving more pillows or blankets, or assisting with water or snacks (of special interest to people with diabetes).

The sleep technologist may also enter your room during the night to:

  • fix a sensor that has fallen or moved, or replace one which is no longer working
  • help you cool down by flipping your pillow or turning on a fan; when a patient sweats too much, it can disrupt the signal tracings coming from the scalp
  • initiate PAP therapy, if you didn’t start off your study using it at Lights Out, as your study data indicates you have sleep-disordered breathing and the doctor has given orders to start therapy

Sleep study: “Lights On”

When at least 6 ½ hours (150 minutes) of sleep has been recorded, your study will be ended by the sleep technologist. They will enter the room and gently awaken you. Then they will return to their place in the lab and ask you to perform the same simple exercises—looking up and down, etc.—that you did the night before.

Directly afterward, they will re-enter your room, help you remove your mask and gently detach all of your sensors.

Many patients believe they are being helpful by removing these sensors, but please resist the impulse. There is a specific way that the sleep technologists remove them that helps them protect the equipment and expedite its cleaning.

At this point, you are free to shower and pack up to leave the study. You will also receive additional paperwork to fill out before you leave and may be offered a light snack or a coupon for breakfast in the hospital cafeteria, if this is where you had your sleep study.

Sleep study: Final advice

Please take caution if you plan to drive yourself home or to work in the event you used a sleep aid the night before. You may still be groggy from the medication and that can lead to drowsy driving and car accidents.

Also note: It’s not advised to ask the sleep technologist to interpret the study results at this time. It’s not within their duties to diagnose patients, as they are not physicians.

Your study data will still need to be analyzed and reviewed by the sleep physician before any results can be confirmed. It’s likely you will leave the lab before your sleep physician even arrives that morning.

You will have probably already set up a follow-up appointment for your test results anyway, when you will meet with your sleep physician to formally review your test results and discuss possible treatments.

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