COPD, or chronic obstructive pulmonary disease, is a chronic, ongoing, progressive disease of the lower respiratory tract in the lungs.The hallmark of the disease is difficulty with breathing that slowly gets worse over time.COPD is a seriously disabling disease with the potential for major complications and is often eventually fatal.COPD is a major cause of disability, and its the fourth leading cause of death in the U.S., according to the National Heart, Lung and Blood Institute.1