In COPD, the airways of the lungs (bronchial tubes) become inflamed
and narrowed. They tend to collapse when you breathe out and can become clogged
mucus. This reduces airflow through the bronchial
tubes, a condition called airway obstruction, making it difficult to move air
in and out of the lungs.
The inflammation of the bronchial tubes makes the nerves in the lungs
very sensitive. In response to irritation, the body forces air through the
airways by a rapid and strong contraction of the muscles of respiration—a
cough. The rapid movement of air in the breathing tubes helps remove mucus from
the lungs into the throat. People with COPD often cough a great deal in the
morning after a large amount of mucus has built up overnight (smoker's
The oxygen and carbon dioxide exchange
The lungs are where the blood picks up oxygen to deliver throughout
the body and where it disposes of carbon dioxide that is a by-product of the
body processes. COPD affects this process.
Emphysema can lead to destruction of the alveoli, the
tiny air sacs that allow oxygen to get into the blood. Their destruction leads
to the formation of large air pockets in the lung called bullae. These bullae
do not exchange oxygen and carbon dioxide like normal lung tissue. Also,
the bullae can become very large. Normal lung tissue next to the bullae cannot
expand properly, reducing lung function.
Chronic bronchitis affects the oxygen and carbon dioxide exchange
because the airway swelling and mucus production can also narrow the airways
and reduce the flow of oxygen-rich air into the lung and carbon dioxide out of
The damage to the alveoli and airways makes it harder to exchange
carbon dioxide and oxygen during each breath. Decreased levels of oxygen in the
blood and increased levels of carbon dioxide cause the breathing muscles to
contract harder and faster. The nerves in the muscles and lungs sense this
increased activity and report it to the brain. As a result, you feel short of
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