Prevalence of Nocturnal Hypoventilation in Obese Subjects Fiited With Continuous Positive Airway Pressure for Obstructive Sleep Apnea / Hypopnea Syndrome

Patients will be monitored using transcutaneous oxy-capnography to evaluate the prevalence of nocturnal alveolar hypoventilation in these population. Nocturnal alveolar hypoventilation is defined with PTcCO2 \> 49 mmHg more than 10% of the time of capnographic recording.

"Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, and the Patient-Reported Hypoventilation Questionnaire."

Arterial blood gas analysis will be performed only in patients presenting nocturnal hypoventilation.

Plethysmography will be performed only in patients presenting nocturnal hypoventilation. It will be used to measure lung volume and assess pulmonary function. This non-invasive procedure involves the patient breathing into a device that measures changes in pressure within a sealed chamber.

The intervention will be performed only in patients presenting nocturnal hypoventilation. Spirometry with a reversibility test will be performed to assess lung function and evaluate the response to bronchodilators. The procedure involves measuring forced expiratory volume and forced vital capacity before and after the administration of a bronchodilator.

Clinical exam will be performed only in patients presenting nocturnal hypoventilation. It will consists of standard interview/clinical examination: vital signs, cardiological, pulmonary, abdominal, neurological examination, search for clinical signs of nocturnal hypoventilation, search for signs of hypoxia/hypercapnia, pulmonary auscultation.