What is COPD?

Chronic Obstructive Pulmonary Disease, or COPD, is a progressive respiratory disease that makes it hard to breathe. “Progressive” means that the disease will get worse over time.

COPD causes your body to produce large amounts of mucus in your lungs. This, in turn, causes coughing, wheezing, tightness in the chest, breathing difficulty, and other symptoms.

The leading cause of COPD is cigarette smoking. Most people who have COPD either smoke or used to smoke. Other factors such as long-term exposure to lung irritants can also contribute to COPD.


Understanding how the lungs work is critical to understanding COPD. When you breathe, air goes down your windpipe into tubes in your lungs called bronchial tubes, or airways.

Within your lungs, the bronchial tubes branch into a multitude of smaller, thinner tubes called bronchioles. These tubes end in bunches of tiny air sacs called alveoli.

Tiny blood vessels called capillaries run through the walls of the alveoli. When air comes into contact with the air sacs, oxygen passes through the sac walls and into the blood in the capillaries. Simultaneously, carbon dioxide moves from the capillaries into the air sacs.


In COPD, less air flows in and out of the airways because of one or more of the following:

  • The airways and air sacs lose their elastic quality.
  • The walls between many of the air sacs are destroyed.
  • The walls of the airways become thick and inflamed.
  • The airways make more mucus than usual, thus clogging them.

The term “COPD” includes two main conditions, namely emphysema, and chronic bronchitis.

In emphysema, the walls between many of the alveoli are damaged or destroyed. As a result, the air sacs lose their shape and become floppy, or the sacs merge into fewer and larger alveoli rather than many tiny ones. This causes a lesser amount of gas exchange in the lungs.


In chronic bronchitis, the lining of the bronchial tube is constantly inflamed and irritated. This causes the lining to thicken. Also, lots of thick mucus forms in the airways making it difficult to breathe.


COPD is a major cause of disability, and it’s the third leading cause of death in the United States. Currently, millions of people are diagnosed with COPD. Many more people may have the disease and not even know it.

COPD is progressive, meaning it develops slowly. Symptoms worsen over time and can limit your ability to do routine activities. Severe COPD may prevent you from doing even basic activities like walking, cooking, or taking care of yourself.

Most of the time, COPD is diagnosed in middle-aged or older adults. The disease is not contagious.

COPD has no cure yet, and doctors don’t know how to reverse the damage to the airways and lungs. However, treatments and lifestyle changes can help you feel better, stay more active, and slow the progress of the disease.