Asthma and Airway Centre

The Asthma Education Handbook

How Asthma Affects the Lungs

Our bodies depend on oxygen to function. Oxygen enters our lungs from the air we breathe. As we breathe in through our mouth or nose, air passes down the trachea then to the lungs. Here the airways, or bronchial tubes, divide in smaller branches as they get deeper into the lungs, ending in small air sacs called alveoli. The alveoli are surrounded by a network of tiny blood vessels called capillaries. Here, oxygen is transferred from the alveoli to our blood. At the same time, carbon dioxide from our blood is transferred to the alveoli and is expelled when we breathe out.

In asthma, airway changes cause obstruction to the free flow of air in and out of the lungs. These changes may produce one or more of the symptoms of asthma such as breathlessness, wheeze, chest discomfort, cough or sputum (phlegm) production. During an asthma attack, the following changes in the airways may be seen:

	The muscles surrounding the bronchial tubes contract excessively (bronchospasm), thus narrowing the airways. The lining is red and swollen (inflamed) causing further narrowing. Sticky mucus secretions block the airways. Image: used with permission from Purdue Frederick
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Inflamed airways are swollen with fluid and inflammatory cells, filled with mucus, and have damage to their lining cells. The combination of bronchospasm (muscles around airways tighten) and inflammation (swelling within the airways) causes the airways to be narrow. It is now well recognized that inflammation is perhaps the most important feature of asthma and is what leads to the irritablity or "twitchiness" of the muscle surrounding the airways.

There may be many factors or "triggers" which set off an asthma attack and they can be different for each person with asthma. People with asthma frequently have a history of allergies and may have family members with asthma or allergies.

At the present time, we have no cure for asthma. However, Researchers are working on developing new medications and research towards finding a cure. In the meantime, the goal of treatment is to keep you feeling well with few, if any, attacks of breathlessness and wheezing with the best possible lung function.

The principles of management are:

Avoidance of triggers where possible
Prompt treatment of acute attacks
Prevention of asthma attacks and symptoms

The Asthma Education Handbook outlines these principles. You should discuss your treatment of asthma with your doctor.

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