Pulmonary and Sleep Clinic


why the sleep study performed?

The test helps diagnose possible sleep disorders, including obstructive sleep apnea (OSA). Your health care provider may think you have OSA because you have these symptoms:

  • Daytime sleepiness (falling asleep during the day)
  • Loud snoring
  • Periods of holding your breath while you sleep, followed by gasps or snorts
  • Restless sleep

Polysomnography can also diagnose other sleep disorders:

  • Narcolepsy
  • Periodic limb movement disorder (moving your legs often during sleep)
  • REM behavior disorder (physically "acting out" your dreams during sleep)

what is a polysomnography (psg)?

Polysomnography is a sleep study. This test records certain body functions as you sleep. Polysomnography is used to diagnose sleep disorders.

A sleep study tracks:

  • How often you stop breathing for at least 10 seconds (called apnea)
  • How often your breathing is partly blocked for 10 seconds (called hypopnea)
  • Your brain waves and muscle movements during sleep

Most people have short periods during sleep where their breathing stops or is partly blocked. The Apnea-Hypopnea Index (AHI) is the number of apnea or hypopnea measured during a sleep study. AHI results are used to diagnose obstructive sleep apnea.

how is polysomonography performed?

A sleep study measures your sleep cycles and stages by recording:

  • Air flow in and out of your lungs as you breathe
  • The level of oxygen in your blood
  • Body position
  • Brain waves (EEG)
  • Breathing effort and rate
  • Electrical activity of muscles
  • Eye movement
  • Heart rate 

what are the different sleep studies that is done?

Polysomnography can be done either at a sleep center or in your home.

at a sleep center

Full sleep studies are most often done at a sleep center.

  • You will be asked to arrive about 2 hours before bedtime.
  • You will sleep in a bed at the center. 
  • The test is most often done at night so that your normal sleep patterns can be studied.
  • A respiratory technician will place electrodes on your chin, scalp, and the outer edge of your eyelids. You will have monitors to record your heart rate and breathing attached to your chest. These will remain in place while you sleep.
  • The electrodes record signals while you are awake (with your eyes closed) and during sleep. The test measures the amount of time it takes you to fall asleep and how long it takes you to enter REM sleep.
  • The test will record the number of times that you either stop breathing or almost stop breathing.
  • There are also monitors to record your movements during sleep 
Patient wired up, sleeping at a sleep center

at home You may be able to use a sleep study device in your home instead of at a sleep center to help diagnose sleep apnea. You will be scheduled for an appointment with the respiratory technician to connect you to the device. Home testing may be used when: You are under the care of a sleep specialist. Your sleep doctor thinks you have obstructive sleep apnea. You do not have other sleep disorders. You do not have other serious health problems, such as heart disease or lung disease.

at home

How do i prepare for the home sleep study?

1. Please DO NOT take any naps during the day of your sleep study.
2. Do not drink any caffeinated beverages during the day of your sleep study. (This includes coffee, tea, and soda with caffeine). Avoid drinking alcoholic beverages.
3. Please arrive at least 15 minutes before your appointment so you have time to get registered.
4. If you are using medications, take them as prescribed by your physician unless otherwise instructed.
5. Please wear a T-shirt or other top that you will be comfortable sleeping in, as the technician will be placing the equipment on around your chest. You must leave here wearing the machine; do not remove the machine until you wake up the following morning. If you remove it and then attempt to put it back on yourself, it is likely the sensors will not be able to measure the type of data needed for the study. Bring a jacket/sweater to cover machine. 6. You will not be able to get machine wet while it is on
7. No nail polish or fake nails on left index finger
8. It is important for you to bring the equipment back the next morning, so we can download the data and get the machine ready for the next patient. You may drop off the machine at the front desk as early as 7 am.

If you have any questions about your appointment for a sleep study, please call the VMC Sleep Lab Coordinator, at (408) 793-2051, Monday – Friday 7:30am – 4:00pm.