More than three million people worldwide die every year from Chronic Obstructive Pulmonary Disease (COPD). When a person has COPD, less air flows in and out of the airways because either they lose their elastic quality or make more mucus than usual, causing clogging. In chronic bronchitis, the walls of the bronchial tubes become thick and inflamed. In emphysema, the walls between the air sacs can be destroyed, reducing airflow. Read more here.