Chronic Obstructive Pulmonary Disease, also known as COPD, is a progressive lung disease comprised of emphysema and chronic bronchitis. In a minority of cases COPD can be caused by exposure to certain irritants, but the overwhelmingly common cause of the disease, which now affects as many as 24 million Americans, is smoking. Early detection and intervention are key—learn about the possible screening devices and procedures that at-risk patients should seek out.