COPD is a lung disease that makes it hard to breathe. COPD stands for chronic obstructive pulmonary disease. It is caused by damage to the lungs over many years, usually from smoking. COPD is a mix of two diseases: chronic bronchitis and emphysema.

Other things that may put you at risk for COPD include breathing chemical fumes, dust, or air pollution over a long period of time. Secondhand smoke is also bad.

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. In emphysema, the air sacs in your lungs are damaged and lose their stretch. Less air gets in and out of your lungs, which makes you feel short of breath.