Polysomnography: definition, indication and interpretation of results

Also read the article: "Sleep apnea - definition, mechanism and treatment"

Polysomnography: definition and mechanism

The polysomnographic examination consists in recording the physiological data of the patient during his sleep in order to understand the origin of his disorders, to consider appropriate treatment.

Polysomnography: analysis of physiological data

Polysomnography aims to study the patient's sleep during its various cycles and phases. The polysomnographic sleep recording collects a lot of information while the patient is asleep:

• Muscle tension is recorded using an electromyogram – electrodes are positioned at the level of the legs or arms.
• Polysomnography with EEG – electroencephalogram – also measures brain activity, through electrodes placed on the scalp.
• The heart rate, observed by electrocardiogram, is performed by electrodes near the heart.
• Respiratory System Activity: a nasal cannula makes it possible to record the air circulation at the level of the mouth and nose. Abdominal and thoracic belts can also be used to record the movements of the breath.
• The activity of the eyes during sleep is observed during polysomnography by electro-oculography, using electrodes placed near the eyes.
• A neck microphone can also be used to measure decibels in case of snoring.

Are also noted during the polysomnography involuntary movements as well as forms of somnambulism, if any.

Polysomnography: zoom on the course of the examination

If home polysomnography exists, this sleep examination is generally carried out at outpatient hospital.

Note: polysomnography at home may be prescribed when the patient's state of health does not allow him to travel.

Polysomnographic sleep recording takes place in 3 steps: p>

1. The patient goes to the hospital before dark.
2. He is equipped with electrodes and belts intended to collect physiological information likely to diagnose his sleep disorders, then placed in a specialized room equipped with a infrared camera to record any form of parasomnia. The patient, most of the time, also wears a nasal mask connected to a continuous positive airway pressure device.
3. The doctor in an adjoining room observes the data recorded by computer. The information is also recorded.

Once the patient wakes up at the end of the night, he leaves the hospital. The ambulatory polysomnography lasts 6 approximately hours in total. Between entering and leaving the hospital, it takes about twelve hours.

Polysomnography and ventilatory polygraphy, what are the differences?

Made for the same purpose as polysomnography, ventilatory polygraphy also allows recording physiological data of the patient during sleep. This examination is nevertheless easier to implement than a polysomnographic recording, insofar as it is systematically carried out at home. Attention, ventilatory polygraphy is a less complete procedure, which can lead to insufficient or falsified results.

Polysomnography: indication for outpatient polysomnography.

Outpatient polysomnography is prescribed, often as a 2^th intention, in order to determine the nature of the patient's sleep disorders – mainly sleep apnea.

Polysomnography downstream of ventilatory polygraphy

When the patient suffers from sleep disorders, he may be prescribed 2 types of medical examinations:

1. Nocturnal ventilatory polygraphy: performed at home, it allows recording ECG, breathing rate, snoring volume, breathing airflow and blood oxygenation during sleep.
2. Outpatient polysomnography: performed in the hospital on an outpatient basis, this examination is prescribed when the results of the nocturnal ventilatory polygraphy are insufficient to establish the correct diagnosis. Thepolysomnography recording can also measure data on brain, muscle and eyepiece.

Although more restrictive for the patient, polysomnography represents the most complete examination in the diagnosis of sleep disorders.

A test to diagnose sleep apnea

Mainly intended to detect sleep apnea, polysomnography is prescribed by the doctor after a consultation, when the patient presents the following daytime symptoms:

• Intense and recurrent drowsiness, difficulty concentrating and drowsiness while driving.
• Headaches and feeling tired on waking.
• High blood pressure.

During the night, the patient expresses the following symptoms:

• Respiratory pauses and nocturnal micro-awakenings.
• Loud snoring.
• Choking and jerky breathing.

Focus on sleep apnea:

Also known as Obstructive Sleep Apnea Hypopnea – OSAS – the Sleep apnea is manifested by frequent pauses in breathing observed during nocturnal sleep. This syndrome is due to an obstruction of the respiratory tract from the back -throat. It involves poor quality sleep, and thus disrupts the patient's daily life to a large extent.

Note: sleep apnea is favored by certain risk factors, the main one being obesity. p>

Polysomnography: analysis of results, reimbursement of the exam, and other sleep tests

Polysomnography: expected results.

By measuring in particular respiratory, cerebral, ocular and muscular activity, polysomnography makes it possible to determine the apnea-hypopnea index (AHI).

• The patient who does not suffer from sleep apnea obtains an AHI less than 5.
• Between 5 and 15, the patient has mild sleep apnea.
• Between 15 and 30, sleep apnea is moderate.
• Above 30, sleep apnea is diagnosed as severe.

Polysomnography: reimbursement by Social Security.

Carried out in the hospital, and monopolizing a room and a doctor all night long, polysomnographic recording involves a significant cost. The price of polysomnography depends on the nature of the establishment – clinic or hospital – and the city where it is performed. It is on average around €1,500. On presentation of a medical prescription, the patient can nevertheless be reimbursed for part of the price: Social Security covers the costs relating to the polysomnography.

Other sleep tests available to the patient:

In addition to polysomnography and ventilatory polygraphy, various examinations can highlight a sleep disorder sleep apnea type:

• The maintenance of wakefulness test: carried out during the day, this examination is performed at using electrodes placed on the patient's scalp.
• Actimetry: the patient wears an actimeter for a long period of time. This device records the movements of the body day and night, in order to compare the time asleep and the time awake.