Chronic Obstructive Pulmonary Disease (COPD) is a chronic, often progressive lung condition in which the main characteristics include inflammation and airway obstruction, particularly during the exhalation or the expiratory phase of breathing.

When we talk about COPD, we are generally referring to two main conditions, Chronic Bronchitis, which is disease of the large airways (bronchi), and Emphysema, which is disease of the small airways and alveoli, the tiny air sacs where gas exchange occurs.