Assessment of Reactance Parameters Measured by the Forced Oscillation Technique for the Bronchodilator Response in Subjects With Chronic Obstructive Pulmonary Disease (COPD)

The aims of this study is : * to assess the bronchodilator (DUOVENT HFA) response of parameters measured by the forced oscillations (FOT) and in particular the reactance parameters related to the presence of a limitation of expiratory flows * to compare the response of the reactance parameters to bronchodilators with the conventional spirometric parameters (FEV1) and inspiratory capacity (IC), and according to the severity of the disease * to assess and compare the relationship between the response to bronchodilators in terms of IC on the one hand and on the other hand in terms of FEV1, reactance parameters (measured by FOT), resistance parameters (measured by plethysmography and FOT) * Assess and compare the relationship between dyspnea intensity assessed by various scales and conventional respiratory function parameters (spirometry, plethysmography, diffusion indices) and parameters measured by FOT