Polysomnography can identify various sleep disorders. What is polysomnography? When is it prescribed? By who ? How is it going? What information does it provide? After reading these few lines, polysomnography will hold no more secrets for you.
What is polysomnography?
Polysomnography is a test to study the physiology of sleep . This test can identify various sleep disorders . It is also called sleep polygraphy; this is a sleep recording during the night, making it possible to identify sleep anomalies, in particular of the respiratory type. It is a complete examination, including several sub-examinations such as the electromyogram of the muscles of the arms and legs, the encephalogram and the recording of the respiratory and heart rhythms. The patient is filmed throughout the examination and his behavior observed by a doctor. Polysomnography is prescribed for patients with symptoms of sleep disorders, such as severe fatigue during the day, drowsiness, concentration problems or even irritability due to severe fatigue.
When can polysomnography be prescribed?
Very often, polysomnography is prescribed for people suffering from snoringor other sleep disorders. It is also often considered in the presence of symptoms of sleep apnea. Apart from sleep apnea , polysomnography is prescribed for people suffering from the symptom of restless legs, insomnia or even narcolepsy. The prescription of the polysomnography examination can be made by a general practitioner, a pulmonologist, a dentist, an orthodontist or an ENT specialist.
How is a polysomnography performed?
Following a medical prescription, the patient is referred to a hospital or a sleep center. It is sometimes possible to carry out the tests at home, on an outpatient basis. In this case, it is called ventilatory polygraphy. It makes it possible to record a certain amount of data and is easier to implement than polysomnography. On the other hand, it is a less complete procedure. It can sometimes lead to distorted or insufficient results.
Generally, the polysomnography examination takes place at night. The patient must therefore arrive at the hospital the day before. Electrodes are placed on his scalp, chest, face, but also on his arms and legs. These electrodes make it possible to measure:
- Brain activity (electroencephalography);
- Ocular activity , i.e. eye movement (electro oculography);
- Muscle activity in the chin, arms and legs (electromyography);
- The activity of the heart (electrocardiography).
A doctor, installed in an adjoining room, observes the data recorded by the devices. The duration of the exam is approximately 6 hours in total. Nevertheless, it is necessary to plan to stay in the hospital for about twelve hours. Other tests may be done to check for sleep apnea or other types of sleep disorders. One can for example prescribe to the patient a test of maintenance of wakefulness. Performed during the day, this examination is performed via electrodes placed on the patient's scalp. Actimetry may also be prescribed. The patient then wears an actimeter, a device that records the movements of the body day and night, continuously over a long period. The results obtained will make it possible to compare the times of sleep and wakefulness.
Reading a polysomnographic recording
The exam also measures some other important factors in identifying the sleep disorder:
- Ventilation , thanks to a cannula placed in the nose (nasal cannula);
- Snoring , thanks to a microphone placed on the neck;
- The activity of the respiratory muscles , thanks to a strap placed at the level of the abdomen and the thorax;
- Oxygen saturation in hemoglobin (level of oxygen present in the blood), thanks to a sensor placed at the end of a finger;
- Involuntary movements related to sleep;
- Daytime sleepiness ;
- The position of the sleeper ;
- Blood pressure .
In general, a single examination is enough to assess the quality of sleep and to detect possible problems. Indeed, polysomnography monitors the waves of the different sleep cycles, muscle movements, the frequency of apnea if present, and the frequency of hypopnea. Using this information, medical personnel can determine an index of apneas and hypopneas and measure the number and duration of apneas during sleep. If the established score is less than 5, the person does not have sleep apnea. On the other hand, for a sign greater than 5 and possibly exceeding 30, the presence of sleep apnea can be established. The higher the number, the greater the sleep apnea.
The study of the various factors can of course make it possible to identify other sleep disorders and to evaluate their seriousness . Polysomnography is an expensive examination. It depends on the nature of the establishment, and the city where it is practiced. It costs 1500 € on average. Performed on medical prescription, polysomnography can however be partially reimbursed. Indeed, the costs relating to polysomnography are covered by social security.