What Is COPD?
COPD, or chronic obstructive pulmonary (PULL-mun-ary)
disease, is a progressive disease that makes it hard to
breathe. "Progressive" means the disease gets worse over
time.
COPD can cause coughing that produces large amounts
of mucus (a slimy substance), wheezing, shortness of
breath, chest tightness, and other symptoms.
Cigarette smoking is the leading cause of COPD. Most
people who have COPD smoke or used to smoke. Long-term
exposure to other lung irritants, such as air pollution,
chemical fumes, or dust, also may contribute to COPD.
Overview
To understand COPD, it helps to understand how the
lungs work. The air that you breathe goes down your
windpipe into tubes in your lungs called bronchial tubes
or airways.
Within the lungs, your bronchial tubes branch into
thousands of smaller, thinner tubes called bronchioles.
These tubes end in bunches of tiny round air sacs called
alveoli (al-VEE-uhl-eye).
Small blood vessels called capillaries run through
the walls of the air sacs. When air reaches the air
sacs, the oxygen in the air passes through the air sac
walls into the blood in the capillaries. At the same
time, carbon dioxide (a waste gas) moves from the
capillaries into the air sacs. This process is called
gas exchange.
The airways and air sacs are elastic (stretchy). When
you breathe in, each air sac fills up with air like a
small balloon. When you breathe out, the air sacs
deflate and the air goes out.
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, which
tends to clog them.
Normal Lungs and Lungs With COPD

Figure A shows the location of the
lungs and airways in the body. The inset image shows a
detailed cross-section of the bronchioles and alveoli.
Figure B shows lungs damaged by COPD. The inset image
shows a detailed cross-section of the damaged
bronchioles and alveolar walls.
In the United States, the term "COPD" includes two
main conditions—emphysema (em-fi-SE-ma) and chronic
bronchitis (bron-KI-tis). (Note: The Diseases and
Conditions Index article about bronchitis discusses both
acute and chronic bronchitis.)
In emphysema, the walls between many of the air sacs
are damaged, causing them to lose their shape and become
floppy. This damage also can destroy the walls of the
air sacs, leading to fewer and larger air sacs instead
of many tiny ones. If this happens, the amount of gas
exchange in the lungs is reduced.
In chronic bronchitis, the lining of the airways is
constantly irritated and inflamed. This causes the
lining to thicken. Lots of thick mucus forms in the
airways, making it hard to breathe.
Most people who have COPD have both emphysema and
chronic obstructive bronchitis. Thus, the general term "COPD"
is more accurate.
Outlook
COPD is a major cause of disability, and it's the
fourth leading cause of death in the United States. More
than 12 million people are currently diagnosed with COPD.
Many more people may have the disease and not even know
it.
COPD develops slowly. Symptoms often 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 people. The disease isn't passed from person to
person—you can't catch it from someone else.
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. |