Aim of this study is to better understand pathophysiology of the alteration of respiratory mechanics and cardiovascular function in obese volunteer subjects. The investigators plan to test this hypothesis with a physiological, interventional study conducted on volunteers by using Electrical Impedance Tomography in a group of patients and magnetic resonance imaging (MRI) in another group.
Inclusion Criteria: * Have a photo identification document * BMI ≥ 35 kg/m2 * Waist circumference \> 88 cm (for women) * Waist circumference \> 102 cm (for men) Exclusion Criteria: * Psychiatric disturbances such as anxiety, depression, schizophrenia requiring pharmacological treatment or hospitalization in the last year * Subjects with any known condition, including claustrophobia or pain, which limits their ability to lie in the MR scanner for the duration of the research study * Known presence of esophageal varices * Recent esophageal trauma or surgery * Known Coagulopathy * History of pneumothorax * Pregnancy * Diabetes * Presence of prosthesis incompatible with MR * Thoracic diameter grater than 70 cm * Resting heart rate (HR) \< 50 or \> 120 bpm and/or systolic blood pressure \< 90 or \> 160 mmHg and/or peripheral oxygen saturation (SpO2) \< 88% * Currently enrolled in another research study