Nocturnal ventilatory polygraphy, prescription, mechanism and interpretation

This test is intended for patients suffering from snoring, hypopneas or sleep apnea. Simpler to perform than polysomnography which requires hospitalization, ventilatory polygraphy is performed at home, outpatient.

Nocturnal ventilatory polygraphy: for whom? for what purpose?

Nocturnal ventilatory polygraphy allows patients with snoring, hypopnea or sleep apnea to analyze several physiological elements during their sleep.
The ronchopathy is favored by relaxation throat tissue during sleep. This causes vibrations called snoring. The complication of this snoring is sleep apnea.

Sleep apnea causes a stoppage or a decrease in the breathing flow. These apneas can be obstructive or neurological. The patient suffers during the night from obstruction of the upper airway or a marked decrease in ventilation. He therefore has breathing difficulties.
The signs of this pathology are mainly headaches, snoring or drowsiness.
We speak of apnea when the respiratory arrest lasts more than ten seconds and a sleep apnea syndrome is observed when the person has at least five apneas in one hour of sleep.

The goal of nocturnal ventilatory polygraphy is to quantify the apneas that occur during sleep and analyze to find out whether or not they are obstructive. When apnea is obstructive, the patient has repeated stops and starts of breathing during the night.
The device highlights various signs of sleep apnea such as snoring, micro-awakenings or hypopnea.

This sleep apnea/hypopnea syndrome is recognized as an important cardiovascular risk factor and in some cases makes treatment against high blood pressure ineffective.

Nocturnal ventilatory polygraphy: mechanism

Nocturnal ventilatory polygraphy is an examination called ambulatory . Nocturnal ventilatory polygraphy is an examination called. a number of sensors are placed on the individual. Sensors are positioned on the neck, on the fingers (ring finger and index), on the abdomen and sometimes on the nose of the subject.

This ventilatory polygraphy provides several measurements:

• pulse oximetry,
• the aerial flow,
• respiratory efforts,
• and ECG.

Ventilation is recorded from cannulas < /a>nasal and allows to realize whether or not there is obstructive sleep apnea.
The sensors located on the abdomen are used to record the thoraco-abdominal movements during the sleep phase .
The sensors placed on the fingers measure oximetry. Oximetry measures the oxygen saturation of hemoglobin. Its purpose is to quantify the consequences of apnea on Sa02(Arterial oxygen saturation). It should be noted that the heart rate can in certain situations also be recorded.
The sensor located on the patient's neck is intended to assess snoring.

Finally, there is a position sensor that notes if the position adopted during the night influences respiratory events.
Nocturnal ventilatory polygraphy does not, however, make it possible to highlight the respiratory efforts of the patient.
Nocturnal ventilatory polygraphy therefore makes it possible to obtain an apnea/hypopnea score, which is also called AHI. Depending on the result obtained, this examination will or will not be sufficient.
When the AHI is greater than or equal to thirty, polygraphy is sufficient. On the other hand, if the AHI is less than or equal to thirty, a polysomnography will be necessary.

Respiratory polygraphy: limits and additional examination.

Nocturnal ventilatory polygraphy is an examination that encounters obstacles. It happens that the sleep is particularly fragmented, the results can be distorted and the apnea index is underestimated.
Very often therefore, respiratory polygraphy is not sufficient. A polysomnography will be regularly prescribed in view of the results of the respiratory polygraphy. Especially when the results of the polygraphy are negative when there was a strong presumption of obstructive sleep apnea syndrome.

Polysomnography is heavier and unlike nocturnal ventilatory polygraphy, it requires hospitalization. If its mechanism is more constraining, its results are more precise and make it possible not only to clearly exclude obstructive sleep disorders but also to go further in research and to highlight sleep disorders. non-obstructive (heavy legs syndrome, depression, etc.)

Polysomnography records many more measurements than simple ventilatory polygraphy.In addition to the measurements recorded during a polygraphy, polysomnography also records the electrical activity of the brain, eye movements, electrical activity of muscles, electrical activity of the heart, and esophageal pressure.
The verification of the data collected will generally be done in several stages. The tracing will be checked for the first time during the night of the exam, a second the next morning and finally the recording as a whole will be analyzed a few days later. p>