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Information relating to asthma is reprinted with permission of PulmonologyChannel.
Asthma is a chronic disease of the lungs and airways that affects an estimated 14 million to 17 million people in the United States. Severe asthma is a serious health concern that can lead to respiratory failure and death. Asthma kills an estimated 5000 people a year in the United States and as many as 470,000 seek hospital treatment for asthma symptoms.

Despite its prevalence, experts differ in the definition of the disease. Clinical authorities typically favor a broad, comprehensive definition. The National Heart, Lung and Blood Institute, for example, defines asthma as:

"a chronic inflammatory disorder of the airways (which)…causes recurrent episodes of wheezing, breathlessness, chest tightness and coughing, particularly at night or in the early morning…usually associated with widespread but variable airflow obstruction that is often reversible, either spontaneously or with treatment."
Organizations geared primarily toward the informational needs of patients usually promote, simpler, more "user-friendly" definitions. The American Lung Association, for example, defines asthma as:

"a chronic disease of the lungs in which the airways overreact to certain factors…by becoming inflamed or obstructed, making it difficult to breathe comfortably."
Other authorities maintain that asthma is not a single disease, but a group of closely related diseases with common clinical symptoms.

Asthma is a condition in which the bronchial tubes in the lungs react to different stimuli by becoming inflamed. These asthma triggers vary and may include exercise, cold air, allergens (such as dust, ragweed, mold, or cat dander), infections, and emotional reactions. Inflammation of the bronchial airways causes them to become constricted and narrowed. This narrowing of the airways, called bronchoconstriction, produces the symptoms: shortness of breath, tightness in the chest, coughing, and wheezing.

Some people suffer asthma symptoms continuously; others experience them only if exposed to triggers. Regardless of the cause, severe asthma is a serious health concern that can lead to respiratory failure and death.