Chronic obstructive pulmonary disease (COPD) refers to a group of lung diseases that block airflow and make breathing difficult.

Emphysema and chronic bronchitis are the two most common conditions that make up COPD. Chronic bronchitis is an inflammation of the lining of your bronchial tubes, which carry air to and from your lungs. Emphysema occurs when the air sacs (alveoli) at the end of the smallest air passages (bronchioles) in the lungs are gradually destroyed.

Damage to your lungs from COPD can't be reversed, but treatment can help control symptoms and minimize further damage.