Polysomnography (sleep study)

Polysomnography is the test or the study performed on a person, who is completely asleep. Hence, It is also known as the sleep study. Polysomnography is basically done to detect sleeping disorders. Polysomnography records the following while a patient is asleep:

  • Breathing cycle (respiration)
  • Heart rate
  • Level of oxygen in the blood
  • Brain waves
  • Muscle tone
  • Leg Movements
  • Eye movements

A polysomnography test may be performed at a sleep center or in a special room in the hospital. The patient is usually asked to come in the late evening for the polysomnography test, in order to record the various sleep patterns while the patient is asleep. The entire process of polysomnography is being monitored and then analyzed by an experienced sleep specialist. Polysomnography test usually records the patient’s body shifts between 2 phases i.e. Rapid eye movement (REM) and Non-rapid eye movement (NREM). Non-rapid eye movement is further divided into 2 stages:

  • Light sleep
  • Deep sleep

While tracking the phase of rapid eye movement (REM), it is usually observed that the activity of the patient’s brain is very high and the only active parts are the breathing muscles and eyes.

While tracking the phase of non-rapid eye movement (NREM), it is observed that the activity of the patient’s brain is quite low. Hence, a person without any sleep disorders will shift between Non-REM to REM phase in every 2 hours, having 4 to 6 sleep cycles each night. The sleep specialist carefully monitors the body reactions and the sleep cycles of the patient, and hence, detect any disruptions in the sleep pattern.


Why it’s done? What are the risks? How to prepare for the procedure? Expected results from the procedure

The normal process of polysomnography starts when the patient falls asleep and this stage is known a Non-REM. During this phase of sleep, the activity of the brain of the patient is recorded. As this phase passes, the activity of the brain gradually decreases. These brain waves are recorded by Electroencephalography (EEG). The movement of the eyes is not much during this stage as compared to the later stage. After 1 to 2 hours, the brain starts becoming active again and the patient enters the REM stage of the sleep. People mostly dream during this stage. A person without any sleep disorders will shift between Non-REM to REM phase in every 2 hours, having 4 to 6 sleep cycles each night. The sleep specialist carefully monitors the body reactions and the sleep cycles of the patient, and hence, detect any disruptions in the sleep pattern. The doctor might advise a polysomnography test if any of the following conditions are observed:

  • Unusual behaviors – The doctor might advise polysomnography if there are any unusual behavior complaints with patient e.g. rhythmic movements, moving around or walking a lot.
  • Narcolepsy – This is a condition in which a patient feels a lot of drowsiness during the day with sudden onset of sleep.
  • Sleep apnea – If a patient has sleep apnea or any other breathing disorder related to sleep, the test is usually prescribed by the physician. The breathing of the patient stops and starts repeatedly, in this sleep condition.
  • REM sleep behavior problems – This is a condition or a disorder in which a person starts acting out the dreams. This abnormality usually happens in the REM stage.
  • Limb movements – This is a sleep disorder, wherein a person involuntarily extends and flexes the legs while he/she is asleep. This periodic limb movement is associated with restless leg syndrome.
  • Unexplained insomnia – This is a sleep disorder, in which a person is not able to take a sound sleep or wakes up frequently during sleep. This is also known as chronic insomnia.

Polysomnography is a safe, non-invasive and painless procedure. It is a sleep test performed on a person who is completely asleep, to detect sleeping disorders. Having any complications with polysomnography is very rare. However, in some cases, a person might get skin irritation due to the adhesive tapes, which are used to attach electrodes or test sensors to the body.

The doctor or the sleep specialist will explain the polysomnography test in detail to the patient. Some of the points to be taken care of are as mentioned below:

Before the procedure:

  • Avoid eating or drinking any caffeinated beverages and also avoid alcohol, especially in the afternoon and the evening before the test. This is because, consuming caffeine and alcohol might change the patient's sleep pattern and make sleep disorder's symptoms more severe.
  • The patient is allowed to wear the night clothes, while the test is performed. The patient is advised, not to wear very tight clothes as these might interfere with the patient’s sleep.
  • The patient is asked to come to the sleep study room and stay overnight.
  • The polysomnography room would be very quiet and dark, to help the patient fall asleep easily.
  • The polysomnography room will have a bathroom attached and the room is not to be shared with anybody else, to avoid any kind of disturbance.
  • This room will be fitted with a camera to monitor all the movements of the patient carefully, after the lights are turned off.
  • The sleep specialist carefully monitors the body reactions and the sleep cycles of the patient.
  • The room is also fitted with an audio system, for the patient to talk to the sleep specialist easily in case of any query.

 

During the procedure:

  • When the patient is ready to sleep, the technologist comes and puts electrodes or test sensors on the patient's temples, scalp, legs, and chest with the help of adhesive tapes. These electrodes are connected to long wires which are further connected to a computer. The wires, connected, are very long and do not cause any problem while sleeping.
  • A small clip-like device will also be attached to the patient's ear or finger, to continuously monitor the oxygen supply in the blood.
  • While the patient is asleep, the following points would be recorded by the sleep technician:
    • Breathing cycle (respiration)
    • Heart rate
    • Level of oxygen in the blood
    • Brain waves
    • Muscle tone
    • Leg Movements
    • Eye movements
    • Body positions
    • Any noises like snoring while sleeping
    • The above-mentioned points are monitored carefully throughout the night and recorded on a graph.
  • In case of any query or emergency, the patient can call the sleep technologist immediately for help.
  • The patients might be put on a positive airway pressure (PAP) machine. This machine is used specifically for patients with sleep apnea, which is a type of breathing disorder related to sleep. In this sleep condition, the breathing of the patient stops and starts repeatedly. Positive airway pressure (PAP) machine consists of a nosepiece (tight-sealing) which helps in delivering a gentle air stream to the patient in order to boost the breathing process while sleeping. Patients undergoing test with the positive airway pressure (PAP) machine would be asked to try the machine once before the sleep study begins so that the patient is not surprised or does not feel uncomfortable when the machine is used later in the night.
  • The patient might not be able to sleep immediately or easily, while in the polysomnography room as compared to home. However, lesser amount of sleep or discomfort in the sleep, while in the test room, would not impact the test results in any way.

 

After the procedure:

  • When the patient wakes up the next morning, the electrodes or the test sensors attached to the body are removed.
  • The patient is allowed to go home in the morning and the patient can resume routine activities normally.
  • The patient is given a follow-up appointment to visit the doctor
  • The sleep specialist carefully monitors the graph of the body reactions and the sleep cycles of the patient, and detects any disruptions in the sleep pattern.
  • The sleep technologist interprets and analyzes the results of the patient and hands it to the concerned doctor, who then consults the results with the patient in the next appointment.

After the test, the doctor or the physician diagnoses and detects any sleep disorders in the patients based on the graphs obtained on the body reactions and the sleep cycles of the patient.

The doctor will discuss the results of the polysomnography test in detail with the patient. If any abnormal behavioral changes in the sleep pattern of the patient, after the polysomnography report are observed, then the doctor might suggest some medications or a treatment plan. The normal test result of polysomnography indicates no or very few signs of episodes of stopped breathing and normal patterns of muscle movements, eye movements, and brain waves during sleep. Also, abnormal test results of the polysomnography indicate abnormal brain waves and muscle movements, thereby causing sleep disorders.

Some of the abnormalities and findings noted from the test are as mentioned below.

  • Eye movements and the brain waves measured, while the patient is asleep helps the physician to assess the impediments in the sleep of the patient, which can be an indicator of multiple abnormalities related to the sleep. Some of the sleep abnormalities, which can be diagnosed, from eye movements and brain waves are REM related sleep disorders and Narcolepsy.
  • The test results can indicate to the physician the correct level of oxygen required by the patient during the sleep and hence, the doctor can prescribe the treatment accordingly.
  • The heart rate changes and the variations in the breathing rate can be indicator of a sleep related disorder known as sleep apnea
  • Other unusual behaviors observed during the sleep of the patient might be a result of multiple disorders and problems related to the sleep
  • There might be other issues observed, related to limb or leg movements, which can be an indicator of limb based disorders in the patient.

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