What to Expect During a Sleep Test (Polysomnography)

How you will know what to expect
Prior to your appointment date, you should receive confirmation from the sleep lab along with some general preparation instructions.  Many general instructions are listed below:

  • Try to conform to your regular daily activities as much as possible on the day of your study.
  • Bring any regular bedtime medications with you. If you take a sleep aid, you should also bring it and let the technologist know that you have it.  Also, be sure to bring a list of all of your current, daily medications.
  • Pack a two-piece pajamas set or shorts and T-shirt for sleep. A two-piece outfit makes it easier for doctors to hook you up to monitors.
  • Do not drink alcohol on the day/evening of your exam, as alcohol can worsen a sleep problem.
  • Limit caffeine after noon on the day of your study, as caffeine may change your sleep habits.
  • Your hair and skin should be free of oil, creams and lotions when you come to the sleep lab. The electrodes used during your study will adhere much better when your skin and scalp are clean.
  • Be sure to bring any other items that you routinely use for your evening and morning routine (toothbrush, make-up remover, etc.) and clean clothes for the morning.
  • You should follow your normal night time routine. If you normally read or listen to music before bed, you are encouraged to bring a book or headphones with you.

Where you will sleep
You will be sleeping in a private room that is set up similar to a hotel rather than a hospital room.  The room will be dark and quiet, and it have a video camera so that your sleep can be monitored from outside the room.  There will also be an audio system so that you can communicate with your sleep technologist during the night.

How your sleep will be monitored
A sleep test gathers a large variety of information that can diagnose many different sleep disorders.  To do this, the sleep technologist will place many sensors in various locations on your body using a mild adhesive.  Below is a summary of what information is collected, the reason for it, and how it is done:

  • Stages of sleep: Your sleep stages will be monitored by recording your brain activity and eye movements.  Recording this information is necessary to evaluate your sleep behavior. In order to do gather this information, small sensors will be attached to various locations on your scalp and forehead.
  • Muscle movement: The muscles in your body react differently during the changing stages of sleep. Excessive or unusual muscle movement is associated with different sleep disorders.  To monitor muscle movement, you will have two small sensors placed in your chin area, and a sensor placed on the shin area of each leg.
  • Air movement: With sleep apnea, there are periods of no air flow from your nose/mouth (apnea). A sensor will be placed in this area to monitor your airflow.
  • Breathing effort: There are different kinds of apneas.  Sometimes, your brain doesn’t send the signal to your respiratory muscles in your chest to breathe (central apnea).  In other instances, your brain may send the signal, but your tongue or tissue in the back of your throat block the air as it tries to get to your lungs (obstructive sleep apnea).  In order to know if either of these situations are happening, a thin soft belt will be clipped around your chest area to monitor your breathing effort.
  • Heart rate and rhythm: Some sleep disorders cause the heart to act differently than normal. During your test, two or three sensors will be placed over your chest area to record your heart’s activity (electrocardiogram).
  • Oxygen levels in your blood: If you stop breathing during your sleep, your oxygen levels may drop below normal. A small probe will be connected to your finger to watch for changes in your oxygen level as you sleep (pulse oximetry).

Getting up in the middle of the night
Even though you will have wires attached to each of the sensors, the wires are long enough that you will be able to move around freely during sleep, and they all connect into one small unit.  If you need to get out of bed, the technologist can easily disconnect the wires from the small base unit for you.

Wearing CPAP during your study
Depending on your insurance and your general health, you will either be ordered a one- or two-night study.  If you are ordered a one night study, the first half of the night will be spent monitoring your sleep. If your study shows that you have sleep apnea, the sleep technologist may need to wake you and place you on CPAP for the second half of the night.

Once you are on asleep on CPAP, your CPAP level will be adjusted (titrated) to eliminate your apneas. In order to prepare you for this possibility, your technologist will help you try out CPAP and various mask styles until you find one that you think you can wear.  This process will occur before you go to sleep and will help you know what to expect if you need to be placed on CPAP for titration during the night.

Your sleep quality in the lab
Many people do not want to have a sleep study because they are afraid that being in a strange environment attached to cords and wires will make it difficult for them to sleep.  Although you may not fall asleep as easily as you would at home or sleep as well, sleep results are not typically affected.

After the sleep study
The sleep technologist will probably wake you between 5 and 6 a.m. to remove the wires so that you can start your day.  You will not be given any results at this time.  The sleep study will be interpreted by a doctor who specializes in sleep medicine and the results will be sent to the physician who recommended that you have the study.  You should ask the sleep technologist if you will need to contact your physician and how long you should wait.