Sleep Study – Everything You Need To Know

What is Sleep Study?

Sleep study is a non-invasive test to record data about your sleep to check whether you are going through any sleep disorder like obstructive sleep apnea by observing your brain and body. It is called a polysomnography or sleep study. This test can be done both at home and at a lab but most people prefer it in a lab as it is much more organized to conduct such tests. A person is called two hours before sleeping to a sleep center or a hospital. It is done in a lab that is made pleasant and dark for sleeping and performing the test.

During the test, an ECG monitor records your brain waves to identify sleep cycles of REM and Non REM or NREM and any other disturbances that may e taking place during the sleep. In addition to it also records the oxygen quantity in your blood, beathing and heart rate as well as eye and leg actions during the test. It records your sleep pattern at night.

Why is it done?

It is done to diagnose certain sleep disorders. Your physician may prescribe you the test if you face difficulty in falling asleep, waking up in the morning, falling asleep during the daytime, snoring. These disorders may include:

  1. Sleep apnea: In this condition, the person experiences obstruction in breathing while sleeping. The Breathing of the person stops and starts repeatedly during the sleep.
  2. Insomnia: The person is facing trouble in falling asleep or staying asleep.
  3. Circadian rhythm disorder: The person may experience insomnia, excessive daytime sleepiness or both.
  4. REM sleep behavior disorder: In this condition, a person acts out dreams during sleep.
  5. Narcolepsy: The person experiences Excessive daytime sleepiness and sudden attacks of sleep during the daytime.
  6. Periodic limb movement disorder or restless leg syndrome: The person may experience involuntary flex in the leg muscles or you can say the legs extend involuntarily while sleeping.
  7. Sleepwalking: The person may start walking or moving around during sleep.

Types of Sleep Study Tests

There are many types of sleep studies that are performed on the patients as per the requirement and the patient’s condition.

  1. All-night sleep study: The all-night study is done to measure how well a person sleeps during the night. During the test, electrodes are attached to the patient’s skin to measure the pattern of breathing, oxygen levels in the blood, muscle activity and functioning of the heart. In addition to this other measurements can also be done on the advice of the doctor.

The technician records the data and after a detailed analysis, the results are    given the other morning. An effective treatment is suggested if the patient is diagnosed with any sleep disorder.

  1. CPAP Titration: After the sleep is conducted the physician may prescribe you with CPAP test. It is done to understand the flow of pressure needed by a patient when he will use the CPAP machine to have a sound sleep without any obstruction. To understand this, the pressure is adjusted throughout the study so as to have the exact result.
  2. Multiple Sleep Latency testing: This study is done after the all-night sleep study test. This test is done to evaluate how often and quickly a patient falls asleep during the daytime. It records the presence and how severe the daytime sleepiness is in a patient. In addition to this, it also measures abnormalities linked with narcolepsy.

It is also performed in the same manner as other tests by attaching the electrodes to the skin to record the brain, heart, and muscle activity. It also takes into account the movement of the eyes. The test is carried out for 7 hours. The test is done in five cycles in which the patient is asked to take a nap of 20 minutes every two hours. The sleep technologist ensures that the patient stays awake during the two hours wake period to have the correct reading.


  1. Maintenance Wakefulness Testing: This test is performed on the people who belong to the transportation industry to check whether they can stay awake while driving or flying. This test is very similar to Multiple Sleep Latency testing as it is also done in 5 consecutive sessions of 40 minutes with a gap of 2 hours in between each session. The major difference between the two tests is that during Maintenance Wakefulness Testing the patient is asked to sit on the bed and stay awake instead of lying down and sleeping.
  2. Epilepsy Monitoring: This test is done best together with the sleep study test or multiple sleep latency testing. The intimation of the test is given to the patient at the time of consultation only. Apart from attaching electrodes on the skin, it is also attached on the scalp with continuous EEG monitoring in conjunction with video monitoring Multiple Sleep Latency testing in case there are chances of seizures. This test can be performed both during the day and night.    

How to prepare for the test?

During the day of the test, you need to follow your regular routine which includes regular diet and daily routine. But apart from that, there are certain things which you need to remember to avoid any disturbance during the test.

It may also be possible that you do not fall asleep easily but the technicians try to make you as comfortable and relaxed as possible. Eventually, everyone falls asleep though it may be possible you take extra time than you usually take to fall asleep.

  • Stay away from caffeine products like coffee, tea, chocolates, and soft drinks after you have your lunch on the day of testing.
  • Do not take alcohol in the evening as it may disturb your sleep.
  • Wash any hair styling products like hair gel before the test.
  • Do not sleep during the day on the day of testing.
  • You need to discuss any medication you are taking as he may ask you to stop it on a temporary basis.

What to bring?

There are certain things which you are in the habit of having at night before you sleep. So it becomes necessary to bring those things with you.

  • You need to bring the medicines that you take regularly before sleeping or in the morning after waking up as per your doctor’s advice.
  • Toiletries
  • Comfortable slippers and sleepwear like pajamas or night suits.
  • Pillow
  • Blanket
  • Book or any other reading material
  • A friend or a family member to make you more comfortable

What to expect from the test?

This test is performed in a private room of a sleep center or a hospital. This test is performed at night so the patient needs to stay overnight for the test. The room stays dark during the test. The room is fixed with a low-light video camera to monitor the activities happening in the room. It is also fixed with an audio system to talk to you and hear from you.

As soon as you get ready for the tests the technician connects the person to the monitoring equipment. The technician fixes sensors on the scalp, temples, chest, and lungs of a person with the help of a tape or glue. These sensors are then connected to the computer with the help of a wire. You can easily move around in your bed. A small clip is also placed on your finger or your ear to check the level of oxygen in your blood.

Other equipment used during the sleep study:

  • EEG (electroencephalogram) to measure and record brain waves.
  • A flat microphone made of plastic to record snoring.
  • Electromyography (EMG) are electrodes applied to the shin or forearm to monitor muscle movement
  • Belts that stretch across the chest and stomach to measure breathing.
  • Electrodes placed near the eye to measure eye movement called electrooculogram (EOG)
  • Electrocardiogram (EKG) to monitor the heart rhythm
  • Nasal airflow sensor to record airflow

Throughout the test the equipment and electrodes monitor brain waves, movements of eyes and muscles, sleep stages, the pattern of breathing and many more. The technician keeps a close watch from the other room throughout the night. If you are in need of any help then you can talk to them through the equipment.

This includes detaching the wire if you need to get up and go to the washroom at night. He may also assist you in any way you like if you wake up in the middle of the night.

During the test the technologist monitors:

  • Brain waves
  • Movement of the eyes
  • Rate of heart
  • Pattern of breathing
  • Blood oxygen level
  • Position of the body
  • Movement of the chest and abdomen
  • Movement of the limbs
  • Snoring or other noise you make during sleep

If sleep apnea is observed then the treatment may start with Dreamstation CPAP to find the appropriate pressure for improved breathing. It delivers constant air pressure to keep the airways open if you experience an obstruction in breathing during sleep.

For some patients, a Bi-level positive airway pressure (BIPAP) machine may be suitable. They deliver two-way pressures while breathing in and breathing out. It delivers more pressure when somebody breathes in and less pressure when somebody exhales.

If given an opportunity then you should try the Positive airway machine (PAP) beforehand so that it doesn’t come as a surprise to you.

It really isn’t easy to fall asleep at the center as you sleep at home because of the change in the ambiance and bed. But it does not bring any change to the result. It is not necessary to sleep the whole night to have accurate results of the sleep test.

In the morning the sensors and other equipment are removed and you may leave for your home to carry on your regular life. You are asked to come for a follow-up.

Sleep Study Results

There are certain aspects of sleep evaluation. They are as follows:

  1. Sleep efficiency: It tells the total number of minutes a person sleeps during the study by the total amount of sleep time recorded. Higher sleep efficiency means a higher percentage of sleep time compared to the awake time.
  2. Apnea-Hypopnea Index (AHI): It calculates sleep apnea and hypopnea that is called partial obstruction. If this index exceeds five in number then it is considered abnormal.
  3. Oxygen Desaturation Index (ODI): ODI records the number of times a person’s oxygen level drops. If it drops below 90 percent, it is considered abnormal. An oxygen concentrator can be of great help for people who experience breathing-related disorders.
  4. Heart Rate: If the heart rate goes below 60 or over 100 then it is considered as abnormal as the normal heart rate falls between 60 and 100.

To summarize the whole result:

  • It records the time you spent in each stage of sleep
  • How many times you wake up during the sleep
  • You have trouble breathing
  • How often you snore
  • Position of the body
  • Movement of the limbs
  • Unusual pattern of the brain activity

The Results

The data and information gathered during the tests are first analyzed by the sleep technologist after the tests are performed. Then the consolidated report is sent to the physician who reviews the whole report. After going through the report he may discuss further evaluation or any treatment that you needed as per the reports

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