The EXDECHO study is the first randomized study evaluating the effect of four body positions on diaphragmatic excursion in obese patients by ultrasound.

The investigators suppose that the course of the right diaphragmatic hemicupola would be increased by an increasingly horizontal position (gradual increase in the diaphragmatic excursion from standing to lying down).

If this hypothesis is confirmed, kinesitherapists will have more informed positioning choices to improve the effectiveness of respiratory rehabilitation.

Inclusion Criteria:

• to have a BMI greater than or equal to 30;
• to have not had intense physical activity during the hour preceding the measurements;
• to be enrolled in a social security plan;
• to give a written consent;
• to have underwent a pre-inclusion medicalexamination.

Exclusion Criteria:

• to have a respiratory pathology unrelated to obesity (sleep apnea syndrome, obesity-hypoventilation syndrome, restrictive ventilatory syndrome with no other known cause);
• to have a cardiac pathology not stabilized by drug treatment and/or resulting in heart failure and/or requiring the fitting of a pacemaker or defibrillator;
• to have a chronic inflammatory disease (rheumatoid arthritis, Crohn's disease, cirrhosis, etc.);
• to have a chest deformity (kyphoscoliosis, funnel chest, etc.);
• to be anactive smoking or former smoker (stopped for less than 3 months and total consumption > 10 pack-years);
• to have an history of major surgery, surgery under general anesthesia for less than 3 months, or minimally invasive surgery for less than 1 year of the thoraco-abdomino-pelvic compartments;
• to have a known sensitivity to monopropylene glycol (substance present in the sterile ultrasound gel);
• temperature of the room in which the ultrasound measurements are carried out below 20°C or above 25°C;
• subject under a measure of legal protection.