COPD is a lung disease that makes it hard to breathe. It is caused by damage to the lungs over many years, usually from smoking.

COPD is often a mix of two diseases:

Chronic bronchitis In chronic bronchitis, the airways that carry air to the lungs bronchial tubes get inflamed and make a lot of mucus. This can narrow or block the airways, making it hard for you to breathe.

Emphysema In a healthy person, the tiny air sacs in the lungs are like balloons. As you breathe in and out, they get bigger and smaller to move air through your lungs. But with emphysema, these air sacs are damaged and lose their stretch. Less air gets in and out of the lungs, which makes you feel short of breath.