Asthma Health Article

Definition

Asthma is a chronic inflammatory disease of the airways in the lungs. This inflammation periodically causes the airways to narrow, producing wheezing and breath-lessness sometimes to the point where the patient gasps for air. This obstruction of the air flow either stops spontaneously or responds to a wide range of treatments. Continuing inflammation makes asthmatics hyper-responsive to such stimuli as cold air, exercise, dust, pollutants in the air, and even stress or anxiety.

Description

Between 16 and 17 million Americans have asthma and the number has been rising since 1980. As many as 9 million U.S. children under age 18 may have asthma. Blacks, Hispanics, American Indians, and Alaskan natives had higher rates of asthma-control problems than whites or Asians in the United States.

The changes that take place in the lungs of asthmatics make their airways (the bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that do not affect healthy lungs. In an asthma attack, the muscle tissue in the walls of the bronchi go into spasm, and the cells that line the airways swell and secrete mucus into the air spaces. Both these actions cause the bronchi to narrow, a change that is called bronchoconstriction. As a result, an asthmatic person has to make a much greater effort to breathe.

Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscle to contract and stimulate mucus formation. These substances, which include histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area. Many patients with asthma are prone to react to substances such as pollen, dust, or animal dander; these are called allergens. Many people with asthma do not realize that allergens are triggering their attacks. On the other hand, asthma also affects many patients who are not allergic in this way.

Asthma usually begins in childhood or adolescence, but it also may first appear in adult life. While the symptoms may be similar, certain important aspects of asthma are different in children and adults. When asthma begins in childhood, it often does so in a child who is likely, for genetic reasons, to become sensitized to common allergens in the environment. Such a child is known as an atopic person. In 2004, scientists in Helsinki, Finland, identified two new genes that cause atopic asthma. The discovery might lead to earlier prediction of asthma in children and adults. When these children are exposed to dust, animal proteins, fungi, or other potential allergens, they produce a type of antibody that is intended to engulf and destroy the foreign materials. This has the effect of making the airway cells sensitive to particular materials. Further exposure can lead rapidly to an asthmatic response. This condition of atopy is present in at least one third and as many as one half of the general population. When an infant or young child wheezes during viral infections, the presence of allergy (in the child or a close relative) is a clue that asthma may well continue throughout childhood.

Allergenic materials may also play a role when adults become asthmatic. Asthma can start at any age and in a wide variety of situations. Many adults who are not allergic have such conditions as sinusitis or nasal polyps, or they may be sensitive to aspirin and related drugs. Another major source of adult asthma is exposure at work to animal products, certain forms of plastic, wood dust, metals, and environmental pollution.

Causes & symptoms

In most cases, asthma is caused by inhaling an allergen that sets off the chain of biochemical and tissue changes leading to airway inflammation, bronchoconstriction, and wheezing. Because avoiding (or at least minimizing) exposure is the most effective way of treating asthma, it is vital to identify which allergen or irritant is causing symptoms in a particular patient. Once asthma is present, symptoms can be set off or made worse if the patient also has rhinitis (inflammation of the lining of the nose) or sinusitis. When, for some reason, stomach acid passes back up the esophagus in a reaction called acid reflux, this condition also can make asthma worse. In addition, a viral infection of the respiratory tract can inflame an asthmatic reaction. Aspirin and drugs called beta-blockers, often used to treat high blood pressure, also can worsen the symptoms of asthma. But the most important inhaled allergens giving rise to attacks of asthma are:

• animal dander
• dust mites
• fungi (molds) that grow indoors

• cockroach allergens
• pollen
• occupational exposure to chemicals, fumes, or particles of industrial materials
• tobacco smoke
• air pollutants

In addition, there are three important factors that regularly produce attacks in certain asthmatic patients, and they may sometimes be the sole cause of symptoms. They are:

• inhaling cold air (cold-induced asthma)
• exercise-induced asthma (in certain children, asthma attacks are caused simply by exercising)
• stress or a high level of anxiety

Wheezing often is obvious, but mild asthmatic attacks may be confirmed when the physician listens to the patient's chest with a stethoscope. Besides wheezing and being short of breath, the patient may cough or report a feeling of tightness in the chest. Children may have itching on their back or neck at the start of an attack. Wheezing often is loudest when the patient exhales. Some asthmatics are free of symptoms most of the time but may occasionally be short of breath for a brief time. Others spend much of their days (and nights) coughing and wheezing until properly treated. Crying or even laughing may bring on an attack. Severe episodes often are seen when the patient gets a viral respiratory tract infection or is exposed to a heavy load of an allergen or irritant. Asthmatic attacks may last only a few minutes or can go on for hours or even days. Being short of breath may cause a patient to become very anxious, sit upright, lean forward, and use the muscles of the neck and chest wall to help breathe. The patient may be able to say only a few words at a time before stopping to take a breath. Confusion and a bluish tint to the skin are clues that the

oxygen supply is much too low and that emergency treatment is needed. In a severe attack, some of the air sacs in the lung may rupture so that air collects within the chest, which makes it even harder to breathe. The good news is that almost always, even patients with the most severe attacks will recover completely.