Severe asthma may be a different form of t...(likely to have more attacks and are more...)

During an asthmatic attack, the airways in the lung narrow and may even close. A person suffering an attack may experience chest tightness, cough, shortness of breath, and wheezing. The airways in the lung, which look something like a tree with many branches, become inflamed and may fill with mucus.

Allergies and infections may cause the inflammation of the airways, and asthmatic attacks are more likely to occur with a cold or during allergy season. Inhaled corticosteroids, which reduce airway inflammation, can reduce the frequency and severity of asthma attacks, and bronchodilators, which relax the muscles in the airways and allow them to open, can relieve asthma for most people. Although asthma mortality rates are low, an attack can cause suffocation and death. There are about 4,200 asthma deaths in the U.S. each year.

If severe asthma is different from milder forms of the disease, and those differences can be identified, it might suggest new treatments. On the other hand, if severe asthma is not different, only a more extreme version of the same disease, then using current treatments more aggressively might work.

Sorkness and his fellow SARP researchers used lung function data collected at 10 research centers that were part of SARP. He examined four aspects of lung function:

• Air flow limitation. A longer period of time is required to exhale a volume of air. This is probably related to airway narrowing and is a hallmark of asthmatics, whether mild, moderate or severe.

• Air trapping. An inability to exhale completely. Most people can exhale about 70% of their lung volume. Air trapping occurs when the exhalation is significantly less than that benchmark. This is related to extreme narrowing and complete closure of airways during an exhalation.

• Reversibility. Most ast
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