What Is Chronic Obstructive Pulmonary Disease (COPD)?

Tired African American man bending over outdoorsChronic obstructive pulmonary disease (COPD) is a lung disease in which the lung is damaged, making it hard to breathe. In COPD, the airways-the tubes that carry air in and out of your lungs-are partly obstructed, making it difficult to get air in and out.

Cigarette smoking is the most common cause of COPD. Most people with COPD are smokers or former smokers. Breathing in other kinds of lung irritants, like pollution, dust, or chemicals over a long period of time may also cause or contribute to COPD.

The airways branch out like an upside-down tree, and at the end of each branch are many small, balloon-like air sacs. In healthy people, each airway is clear and open, the air sacs are small and dainty, and both are elastic and springy. When you breathe in, each air sac fills up with air, like a small balloon, and when you breathe out, the balloon deflates and the air goes out. In COPD, the airways and air sacs lose their shape and become floppy. Less air gets in and less air goes out because:

•The airways and air sacs lose their elasticity (like an old rubber band)
•The walls between many of the air sacs are destroyed
•The walls of the airways become thick and inflamed (swollen)
•Cells in the airways make more mucus (sputum) than usual, which tends to clog the airways.

COPD develops slowly, and it may be many years before you notice symptoms like feeling short of breath. Most of the time, COPD is diagnosed in middle-aged or older people, and is a major cause of death and illness throughout the world.