Sleep apnea-hypopnea syndrome (SAHS) is a disorder of nocturnal ventilation due to the occurrence abnormally frequent pauses in breathing. It is a public health problem that currently affects 13 % of men and 6% of women between 30 and 70 years old. Sleep apneas are conventionally divided into obstructive and central apneas, depending on the persistence or no respiratory movements and the existence or not pharyngeal collapse during apnea. There are upper airway characterization studies (VAS) in patients with syndrome sleep apnea/hypopnea (OSAS). These physiological characterization studies (measurement of critical closing pressure (Pcrit) of the VAS) and anatomical (transcutaneous ultrasound of the muscles of the floor of the mouth, the base of the tongue, or by a acoustic pharyngometry of the VAS) are interested separately to different parameters without searching correlation with the severity of sleep apnea nor their potential as a screening tool for OSAS in patients at risk. The investigators hypothesize that a strong correlation and constant exists between the physiological collapsibility of VAS, the anatomical measurements of the VAS and the degree of severity of OSAS. Thus, the aim of this descriptive study is to characterization as complete as possible of the VAS of apneic patients in a homogeneous population and a better understanding of the pathophysiological obstructive events in patients without factor obvious risk.

Obstructive sleep apnea-hypopnea syndrome (OSAS) is a nocturnal respiratory disorder caused by a succession of respiratory pauses. The prevalence of OSAHS has increased over the past two decades partly due to the fact that it is more often diagnosed but also due to the progression of obesity. It now affects 13% of men and 6% of women between the ages of 30 and 70. Sleep apneas are conventionally divided into obstructive and central apneas, depending on whether or not respiratory movements persist and whether or not there is pharyngeal collapse during the apnea. Continuous positive airway pressure (CPAP) ventilation via a nasal or naso-buccal mask is the reference treatment. The effectiveness of CPAP is directly linked to its observance. A well conducted treatment allows a significant improvement of symptoms related to OSAHS and effectively reduces daytime sleepiness. In the longer term, it would provide protection against cardiovascular events.

The physiopathology of obstructive apnea has been the subject of in-depth studies; the most recent data show that it is a multifactorial disease. Among the factors implicated, the investigators can cite pharyngeal anomalies (anatomy and collapsibility), a significant ventilatory response ("high loop gain") in response to variations in partial pressure of CO2 (pCO2), a weak pharyngeal muscle response during sleep and a high wakefulness threshold. Each of them can be evaluated by different methods: anatomy by a standardized clinical examination and imaging techniques, some of which have not yet been the subject of anatomo-functional correlation studies (such as the ultrasound or acoustic pharyngometry); collapsibility by measuring the critical closure pressure (Pcrit) (pressure applied at which closure of the airways is observed); the ventilatory response by analysis of the SpO2 and PCO2 signals in the exhaled air (PETCO2) in calm ventilation and ventilatory slope of response to hypercapnia; pharyngeal electromyogram and polysomnographic analysis.

The respective importance of these factors seems to vary greatly from one individual to another, but their characterization would make it possible to propose new avenues of treatment targeting the "loop gain", the pharyngeal muscle tone or the arousal threshold, and d adapt these targets to each patient for a personalized treatment.

The investigators hypothesize that a correlation exists between the physiological collapsibility of the VAS, the anatomical measurements of the VAS and the degree of severity of OSAHS. The objectives of our study are to identify clinical and physiological phenotypes of apneic patients, with the prospect of screening tools, a better distribution of targeted diagnostic and therapeutic resources.

Inclusion criteria: - Any patient, consulting the sleep department of the Bichat hospital for suspected sleep apnea syndrome

• Patient for whom an PSG are prescribed as part of care
• Age ≥18 years and ≤85 years Exclusion criteria: - Recent ENT surgery (less than 6 months)
• Pregnancy in progress (declared)
• Pulsed oxyhaemoglobin saturation < 88% at rest on awakening
• Allergy to ultrasound gel
• Patient with difficulties in understanding the French language
• Vulnerable patient (guardianship, curators)
• Lack of affiliation to a social security scheme
• Lack of information and collection of informed, written and signed consent
• Patient under AME