Chronic obstructive pulmonary disease (COPD) is a progressive lung disease that makes it difficult to breathe. The term COPD comprises several diseases the two most prevalent being emphysema and chronic bronchitis. Most people diagnosed with COPD have a combination of both. One of the most common symptoms of COPD is a chronic cough and excess mucus production. This chronic cough can lead to tightness of the chest, wheezing, and shortness of breath.