Controlling Asthma: Inflamed Airways

by Food and Drug Administration (FDA)

Think of someone — a child or an adult — racked by uncontrolled coughing. With a heaving, distended chest, neck muscles straining, and eyes showing alarm verging on panic, the person can utter only a few brief words between rasping, wheezing, frantic efforts to breathe.

The person puts a tubelike device in his or her mouth and inhales twice. Within minutes, remarkably it seems, the crisis is over. Breathing returns to normal. The person can go back to school or work or even jogging — until the next attack, which might be hours or months away.

Asthma attacks are often milder than this description — just a shortness of breath that soon passes without treatment. But they can also be much, much worse, requiring a hurried trip to the hospital for emergency — sometimes lifesaving — care. Even in severe cases, hospital treatment usually enables asthma patients to regain near-normal breathing. But not always. More than 5,000 asthma deaths were reported in the United States in 1997, according to the American Lung Association (1997 is the most recent year for which statistics are available). Most of the deaths occurred in patients who misjudged the severity of symptoms or failed to reach a hospital or clinic in time to prevent respiratory failure.

Although African-Americans make up less than 13 percent of the U.S. population, they account for nearly 22 percent of deaths due to asthma, according to the American Lung Association.

For reasons that are not well understood, the number of newly diagnosed cases of asthma in the United States is rising sharply, up 58.6 percent between 1982 and 1996. Asthma deaths, too, are climbing — 5,434 in 1997 compared with 2,598 in 1979. While not accounting for the rising prevalence of asthma, the lack of necessary health care, especially among the urban poor, may play an important role in the rising asthma death rate.

Ironically, these increases are taking place at a time when some irritants believed to be associated with asthma — such as air pollution, dust, molds, and tobacco smoke — are better understood and often under better control than they once were. The reason for the increases remains a mystery, but some investigators think one contributing factor is modern, tightly sealed homes and workplaces that trap and recirculate contaminants, increasing exposure to them in the air we breathe.

Inflamed Airways

Most of America's estimated 17 million people with asthma, of whom almost 5 million are under age 18, mildly affected. About a quarter of asthmatic children seem to "outgrow" their disease in their teen years or as young adults. It's not certain, however, that they are completely free of asthma. Studies of people with late-onset asthma — asthma that first shows up in the fifth or sixth decade of life or even later — have found that many of them experienced asthma-like breathing difficulties as children.

There is no known cure, but asthma often can be well-controlled by a strategy aimed at preventing acute episodes and halting those that do occur.

This two-pronged attack is increasingly effective because scientists are piecing together a more comprehensive picture of the nature of asthma and gaining new insights into the cause, prevention and management of acute asthma attacks. New information is changing the way practicing physicians and the Food and Drug Administration view the role of drugs in asthma treatment and prevention.

Changing Theories

Until the 1970s and early 1980s, asthma was understood to result from over-responsiveness of the tubes (bronchi and bronchioles) that carry air to and from the lungs. People with hypersensitive airways, when exposed to certain irritants called "triggers" — such as household dust, tobacco smoke, cat fur (dander), cockroach droppings, air pollutants, even vigorous exercise or cold air — would experience "bronchospasm," a narrowing of the airways caused by contraction of the muscles that encircle the bronchial tubes.

Asthmatics also tend to produce thick, sticky mucus and have inflamed, damaged airways, both of which worsen the breathing restriction caused by bronchospasm. (This is illustrated in a 42K PDF file.) During an acute attack, asthmatics seem to have a hard time getting their breath. Actually they are struggling to push air out of over-inflated lungs through constricted airways.

That understanding of asthma led to treatments aimed primarily at opening up the bronchial tubes by using drugs that cause the bronchial muscles to relax their grip on air passages. Bronchodilators are still a mainstay of asthma therapy. But Robert Meyer, M.D., of FDA's Center for Drug Evaluation and Research, notes that scientists' understanding of asthma has changed significantly over the last decade or so.

He points out that since the early 1980s, increasing scientific evidence shows that inflammation is as much responsible for bronchospasm as anything else. Today, Meyer says, "putting primary emphasis on controlling bronchospasm rather than chronic airway inflammation looks like "putting the cart before the horse".

The evidence Meyer refers to strongly indicates that asthma is a chronic inflammatory disease that usually develops within the first few years of life. Much of this evidence is discussed by H.W. Kelly of the University of New Mexico College of Pharmacy in the October 1992 issue of the Journal of Clinical Pharmacology and Therapeutics. Kelly is a member of FDA's Pulmonary and Allergy Drugs Advisory Committee.

In people with asthma, whether mild or severe — even in asthmatics whose first acute attack occurs long after childhood — the air passages are continuously inflamed, causing them to be swollen and to react strongly to inhaled irritants. But because patients may not be aware of any symptoms, this inflammation is sometimes called "the quiet part" of asthma.

People with chronically inflamed airways may show no outward signs of asthma until the first acute attack requires urgent medical attention, often at a hospital emergency department. Emergency care physicians and nurses — who are all too familiar with acute asthma — are able to administer powerful drugs to open the patient's air passages and restore more normal breathing. They are likely to recommend the patient be seen by an asthma specialist, who can devise a combination of treatment and prevention measures aimed at avoiding or minimizing further acute asthma attacks. The first step in that process is an accurate diagnosis.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.