 The diaphragm pathophysiological changes occurring in chronic obstructive pulmonary disease COPD leads to functional inefficiency that strongly correlates to the loss of lung function. Muscle fiber shortening follows lung hyperinflation, resulting to a chronic mechanical disadvantage, which worsens in COPD exacerbations. The DM is mostly assessed with techniques that exposes the patient to risks. The ultrasonography on M-mode is easy to use, safe and measures directly the diaphragmatic dome displacement. The study aim to determine whether the COPD impairs the DM, and verify improvements after an inpatient PR. 