Chronic Obstructive Pulmonary Disease (COPD) called as Chronic Obstructive Airway Disease. COPD is characterized by difficulty in exhaling air. It is slowly progressive disease and irreversible. The most common cause of COPD is Cigarette Smoking. COPD may include diseases that cause airflow obstruction (eg., Emphysema, Chronic Bronchitis) or combination of these disorders.