What is Chronic Obstructive Pulmonary Disease (COPD)?

 

doctor with arms folded around chestChronic 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. (See the section, “How Do the
Lungs Work,”
for details.) 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.

COPD is a major cause of
death and illness throughout the world. It is the 4th leading cause of
death
in the U.S. and the world.

There is no cure for COPD. The
damage to your airways and lungs cannot be reversed, but there are things you
can do to feel better and slow the damage to your lungs.

COPD is not
contagious-you cannot catch it from someone else.

Other Names for
COPD

  • Chronic obstructive airway disease
  • Chronic obstructive lung disease

In the U.S., COPD includes:

  • Emphysema
  • Chronic Bronchitis

In the emphysema type of COPD, the walls
between many of the air sacs are destroyed, leading to a few large air sacs,
instead of many tiny ones (see How Do the Lungs Work). Then, the lung looks like
a sponge with many large bubbles or holes in it, instead of a sponge with very
even tiny holes. These few large air sacs have less surface area than the normal
tiny ones for the exchange of oxygen and carbon dioxide. Poor exchange of the
oxygen and carbon dioxide causes shortness of breath.

In chronic
bronchitis, the airways have become inflamed and thickened and there is an
increase in the number and size of the mucus-producing cells. This results in
excessive mucus production, which in turn contributes to cough and difficulty
getting air in and out of the lungs.

Most people with COPD have both
chronic bronchitis and emphysema.

How Do the Lungs Work?

The lungs provide a very large surface area (the size of a football
field) for the exchange of oxygen and carbon dioxide between the body and the
environment.
.

Normal lung function. A slice of normal lung
looks like a pink sponge-filled with tiny bubbles or holes). Around each bubble
is a fine network of tiny blood vessels. These bubbles, surrounded by blood
vessels, give the lungs a large surface to exchange oxygen (into the blood where
it is carried throughout the body) and carbon dioxide (out of the blood). This
process is called gas exchange. Healthy lungs do this very well.

Here’s
how normal breathing works:

  • You breathe in air through your nose and mouth. The air travels down through
    your windpipe (trachea) then through large and small tubes in your lungs called
    bronchial (BRON-kee-ul) tubes. The larger ones are bronchi (BRONK-eye),
    and the smaller tubes are bronchioles (BRON-kee-oles). Sometimes the word
    “airways” is used to refer to the various tubes or passages that air must travel
    through from the nose and mouth into the lungs. The airways in your lungs look
    something like an upside-down tree with many branches.

 

  • At the ends of the small bronchial tubes, there are groups of tiny air sacs
    called alveoli (al-VEE-uhl-EYE). The air sacs have very thin walls, and
    small blood vessels called capillaries run in the walls. Oxygen passes from the
    air sacs into the blood in these small blood vessels. At the same time, carbon
    dioxide passes from the blood into the air sacs. Carbon dioxide, a normal
    byproduct of the body’s metabolism, must be removed.

 


The
airways and air sacs in the lung are normally elastic-that is, they try to
spring back to their original shape after being stretched or filled with air,
just the way a new rubber band or balloon would. This elastic quality helps
retain the normal structure of the lung and helps to move the air quickly in and
out. In COPD, much of the elastic quality is gone, and the airways and air sacs
no longer bounce back to their original shape. This means that the airways
collapse, like a floppy hose, and the air sacs tend to stay inflated. The floppy
airways obstruct the airflow out of the lungs, leading to an abnormal increase
in the lungs’ size. In addition, the airways may become inflamed and thickened
and mucus-producing cells produce more mucus, further contributing to the
difficulty of getting air out of the lungs.

In the type of COPD called
emphysema, the walls between the air sacs are destroyed, leading to a few large
air sacs, instead of many tiny ones. Then, the lung looks like a sponge with
large bubbles or holes in it instead of a sponge with very even tiny holes.
These few large air sacs have less surface area than the many tiny ones for the
exchange of oxygen and carbon dioxide.

What Causes COPD?

Smoking is the most common cause of COPD.

Most cases of
COPD develop after repeatedly breathing in fumes and other things that irritate
and damage the lung and airways. Cigarette smoking is the most common irritant
that causes COPD. Pipe, cigar, and other types of tobacco smoking can also cause
COPD, especially if the smoke is inhaled. Breathing in other fumes and dusts
over a long period of time may also cause COPD. The lungs and airways are highly
sensitive to these irritants. They cause the airways to become inflamed,
narrowed, and destroy the elastic fibers that allow the lung to stretch, then
come back to its resting shape. This makes breathing air in and out of the lungs
more difficult.

Other things that may irritate the lungs and contribute
to COPD include:

  • Working around certain kinds of chemicals and breathing in the fumes for
    many years
  • Working in a dusty area over many years
  • Heavy exposure to air pollution.

Being around secondhand smoke
(smoke in the air from other people smoking cigarettes) also plays a role in
causing COPD.

Genes, tiny bits of information in your body cells passed
on by your parents, may play a role in developing COPD. In rare cases, COPD is
caused by a gene-related disorder called alpha 1 antitrypsin deficiency. Alpha 1
antitrypsin is a protein in your blood that inactivates destructive proteins in
the blood. People with antitrypsin deficiency have low levels of alpha 1
antitrypsin; the imbalance of proteins leads to the destruction of the lung and
COPD. If people with this condition smoke, the disease progresses more
rapidly.

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