Chronic obstructive pulmonary disease is a general term for many lung diseases that affect breathing. It refers to lung diseases that are chronic (long term), progressive (developing) and mostly irreversible. The most common lung diseases included under this term are emphysema and chronic bronchitis.
COPD damages the airways that carry air to the lungs. The airway walls become narrowed and swollen, therefore obstructing the airflow in and out of the lungs. Some forms of COPD can scar the lungs and lead to increased airway resistance, while others induce the excessive secretion of phlegm that the lungs are not able to clear.