Polysomnogram overview

Polysomnography is a special study of your sleep. It records your brain activity, eye movements, breathing, heart rate, oxygen level, and chin and leg muscle movement patterns.

For the sleep study, you will spend the night at a sleep center. The study has little to no discomfort, and it will last for at least six hours.

Purpose of the sleep study

The sleep study will help your doctor tell if you have a sleep disorder. He or she will order this test to:

  • understand your sleep patterns to see if you have a sleep-related breathing disorder such as sleep apnea (stopping breathing many times at night)
  • see if you have any sleep-related behaviors or movements such as abnormal arm or leg movements, sleepwalking or talking
  • go along with a multiple sleep latency test (known as an MSLT) to see if you have narcolepsy (extreme sleepiness during the day with possible loss of muscle tone).

Parts of the sleep study

When you arrive for your sleep study the technologist will apply adhesive patches and sensors to your skin. Each patch and sensor has a wire that connects to a recording device. The recorded information will be sent to a computer for review.

Information being collected includes the following.

  • Brain activity: Tiny electrodes will be attached with a special paste or adhesive to your scalp. The electrodes will record your brain waves during the different stages of sleep:
    • light sleep
    • deep sleep
    • rapid eye movement (known as REM sleep), during which you dream.
  • Eye movements: Electrodes will be placed near your eyes. The computer will record your eye movements during sleep.
  • Face and leg activity: Electrodes will be placed on your face and legs. The computer will record muscle tension, teeth grinding and leg movements.
  • Airflow: Small electrodes will be placed near your nose and mouth. The computer will record the flow of air from your nose and mouth.
  • Respiratory effort: Electrodes with a belt will be placed around your chest and abdomen. The belt wires will record your chest and abdominal movements when you breathe. The test is used with the airflow sensor to confirm sleep apnea.
  • Heart rate and rhythm: EKG (electrocardiogram) patches will be placed on your chest. The computer will record your heart rate and rhythm.
  • Oxygen levels: A pulse oximeter sensor will be placed on your finger. The sensor will record the amount of oxygen in your blood. If you have sleep apnea, this test will show if your oxygen level is affected when you stop breathing.
  • Snoring: A sensor will be placed on your face, your throat, or the lower part of your neck. The computer will record your snoring.

An audio/video camera on the wall will record the sounds in your room, your sleep positions during your sleep and the different movements you make.

A technologist will be in a control room with the monitors and computers that record your sleep. He or she will be available to help you at any time during the sleep study. There is an intercom/microphone in the room to let you communicate with the technologist during the test.

Home Sleep Apnea Test overview

A Home Sleep Apnea Test is a much more limited version of the Polysomnogram. During this test, we only measure things related to your breathing. Airflow, respiratory effort, heart rate, snoring and oxygen levels are measured. But, face and leg activity, eye movements and brain activity are not measured. 

Since the amount of equipment is significantly reduced, patients (after some brief instruction) are able to put their own monitors on themselves. You meet with one of our sleep testing experts, who will teach you how to use the equipment. You bring it home, put it on and return it the next business day. While you sleep, it will record your breathing pattern. The sleep testing experts will then download the data you have collected and submit it to our sleep medicine physicians for their expert review.

Source: Allina Health's Patient Education Department, Polysomnography (Sleep study), neuro-ahc-23688
Reviewed By: Michael Schmitz, PsyD, LP, CBSM, and Andrew Stiehm, MD, Allina Health
First Published: 04/01/2006
Last Reviewed: 03/22/2016