COPD (chronic obstructive pulmonary disease) is an incurable but treatable lung disease that tends to develop slowly and worsen gradually. Having COPD means that the lungs have developed permanent changes that affect the body's ability to exhale properly. This can eventually affect the ability to do everyday activities including walking, working, and handling self-care tasks. COPD is the fourth leading cause of death in the U.S.

People with COPD tend to get out of breath easily, and they may have to give themselves extra time to breathe out slowly. Due to damage to the lung structure, extra air is often trapped in the lungs, making it difficult both to inhale oxygen and to exhale carbon dioxide as efficiently as a healthy person can.

There are two main types of COPD, affecting slightly different parts of the lungs: chronic bronchitis and emphysema. Typically, people with COPD have both of these diseases, which is why the more general term COPD has become the preferred usage.

COPD isn't reversible, but it is treatable. The purpose of treatment is to slow the disease's progression, and to prevent exacerbations, or flare-ups. For those who smoke, quitting slows the disease process.