Asthma affects about 7.5 percent of adults in the U.S. and is responsible for 1.8 million hospitalizations and 10.5 million physician office visits per year. It is more common in black people (8.7 percent) and Puerto Rican Hispanics (13.3 percent) than in white people (7.6 percent). Asthma presents as episodic or persistent symptoms of wheezing, shortness of breath, air hunger, and cough. Symptoms may be precipitated or worsened by exposure to allergens and irritants, viral upper respiratory tract infections, bacterial sinusitis, exercise, and cold air. Asthma may develop at any age but its onset is more commonly seen in children and young adults. Familial clusters do occur suggesting an as-yet undiscovered genetic factor. Risk factors for asthma include a family history of it, viral infections in the first three years of life, and socioeconomic factors such as low income level, cockroach or rodent infestations in the home, and access to medical care. In addition exposure to tobacco smoke is a common exacerbating factor.
The airways in the lung, called bronchi, like arteries, have smooth muscle tissue in their walls. In response to a trigger, the airways in those with asthma constrict. This is called airway hyperresponsiveness, which is an exaggerated reduction in airway caliber after a stimulus. This was discovered by Claudius Galen, a Roman physician, in AD 150. Airway hyperresponsiveness may be induced by allergens (e.g., pollen and animal dander), chlorine, pollutants (e.g., sulfur dioxide), diesel exhaust particulates, and viral upper respiratory infections. Another important factor in asthma is airway inflammation, which is caused by multiple types of white blood cells invading the airways in response to a stimulus.
Asthma is diagnosed by using the patient’s symptoms and physical examination in combination with spirometry. Spirometry, in which the patient must repeatedly blow into a tube, measures factors like total lung air capacity and various types of airflow. It also measures whether or not those measurements improve after the patient uses a rescue inhaler. Unlike emphysema, in which reduced airflow is permanent, airflow reductions in asthma are reversible.
The mainstay of asthma treatment is short-acting B2-agonists like albuterol. When inhaled, the B2-agonists act on receptors in the airway walls causing the smooth muscle to relax, thereby causing the airway to dilate. Often, if the use of an inhaler is not enough to control symptoms, an inhaled steroid (i.e. Advair) is added. Because asthma is often linked to allergies, the use of a mast cell inhibitor like Singulair, which treats both asthma and allergies, can be helpful. In severe cases, oral or intravenous steroids like prednisone must be used.
Smoking tobacco products can impair the effectiveness of steroids used to treat asthma. And since tobacco smoke causes airway inflammation, smoking makes symptoms worse. Anyone who has asthma and smokes, even e-cigarettes, needs to have their head examined. Lastly, if you use an inhaled steroid be sure to rinse your mouth out after using the inhaler as this prevents the development of a mouth condition called thrush.
For more information go to www.cdc.gov/asthma or www.nhibi.nih.gov/files/docs/guidelines/asthgdln.pdf
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