Sleep Study (Polysomnogram)

During a routine medical check -up, your doctor asks you questions about your sleep and you might tell him or her that you feel tired or sleepy during the day; you might suffer from insomnia. The doctor wants to order a sleep study. A sleep study helps your doctor find out about the quality of your sleep and see if there is a sleep disorder such as sleep apnea, snoring or leg jerks or find out why you are waking up so much.

The medical term for a sleep study is the polysomnogram (PSG) which is typically performed during the night, though in special cases (shift workers), it can be performed during the day. PSG records your sleep stages, information about your breathing and oxygen level and body movements.

The study is typically performed in a sleep laboratory. Don’t worry, there are no experiments going on in the “lab”; but other names include “sleep center”. Technicians will monitor you through a monitoring room. Occasionally, the study is performed in appropriately equipment hotel rooms.

When you arrive to the sleep lab or center in the evening, a technician will greet you and be responsible for your care for that night. You will have your own room, (not much different from a hotel room) with a bed (of course!) and television.  The bathroom is often inside your room but in few centers, it might be shared. When you get in your room, you will be given the chance to change to your pajamas, get settled and fill out few paper work and questionnaires.

Soon, the technician will return to apply some wires and electrodes that  record your brain waves, breathing and other body functions. No needles are involved in this procedure. The technician will apply small metal disks to your head in between your hair lines using adhesives or a glue. Don’t worry, they are removable in the morning. Metal disks will pick up electrical recording that are sent from your brain, which are then recorded as an EEG (electroencephalogram) and are interpreted by the technicians and doctors. These electrodes and wires are not painful though annoying to some, but most people tolerate them well. Soon everyone falls asleep.

When all the hook up is complete, you are left alone to relax, perhaps to watch TV or read a book or magazine. Around 10 or 11 pm the technician would like to turn the lights off and allow you to fall asleep and start the PSG recording. 

Don’t worry, you will still be able to go to the bathroom when nature calls. The wires are hooked up in a small box which can be disconnected. All you have to do is use the bell and the technician come in and disconnect the box and you are ready to go. A bedside urinal might be needed for some individuals who have physical limitation; be sure to ask for one.

The technician will wake you up in the morning around 6 or 7 am depending on the facility. You can go to work or home. Ask if they run studies on weekend if that is more convenient for you.

In the meantime, a physician who is a specialist in sleep medicine will analyze the information and produce a report called the sleep study report. Make sure to contact or follow up with your ordering physician to go over the results of the study. The sleep medicine physician might be the ordering doctor in which case you follow up with him/her.


So what does a sleep study help me as a sleep medicine doctor to help you in your sleep?

The EEG (electroencephalogram) tells me alpha, beta, theta and delta which are brain waves that decide whether you are awake or in stage 1, 2, REM or deep sleep. The EEG leads are placed on your scalp.

The EMG (electromyogram) gives information about muscles in the legs, arms or the jaw. For example teeth grinding (bruxism) can be seen when the jaw EMG leads move in a certain way.

EOG (electro-oculogram) record the movements of your eyes which is important in determining sleep stages along with the EEG. They are placed on the outer sides of your eyes.

EKG (electrocardiogram) wire is also applied to monitor your heart beat since some sleep disorders especially sleep apnea are associated with problems in heart rhythm.

Snore microphone records snoring. The wires are attached to the side of your neck.

Nasal airflow wires record your breathing by sensing the temperature and pressure of your breathe. They are placed near your nose and mouth.

Chest and abdominal belts record the breaths that you take as your chest and abdomen rise up and down.

Oximeter is an oxygen monitoring probe that is applied to your finger and  eometimes attached to your ear. It records your blood oxygen saturation. If you have sleep apnea, oxygen saturation typically drops.

Video records your body position or any behavior during sleep such as dream enactment or leg movements.

Tips on how to prepare for your sleep study:

  • Avoid caffeine, alcohol and napping the day because they interfere with your sleep.
  • Take all the necessary medications that you usually take at night, unless instructed not to during the study by your physician.
  • Take a shower before your come to the sleep lab.
  • Do not use oils, creams or lotions on your face or hair.
  • Eat dinner in the evening before you come but you can bring a light snack.
  • Bring your pajamas and toothbrush or other nighttime items that you need.
  • You may bring your own pillow if you wish, even though you will be provided with one. Some people like to bring their own blankets.
  • Relax. You will fall asleep and next thing you know it is morning.