Asthma Health Article

Definition

Asthma is a chronic inflammatory disease of the airways in which periods of relatively free breathing are punctuated by episodes in which breathing becomes difficult. During an attack, inflammation causes the airways to fill with mucus secretions and become obstructed. Asthmatics cough, gasp for air, wheeze, gag, and feel choking sensations as they struggle to breathe. Obstruction to airflow usually responds to a wide range of treatments.

Depending of the type of asthma, attacks may be triggered by environmental factors such as cold temperatures, air pollution, smoke, pollen, dust, mildew, mold, and animal hair or dander. Exercise, allergic reactions, respiratory infections, and emotional stress may also trigger attacks. Like other chronic diseases, asthma can be controlled, but not cured.

According to the American Lung Association, in 1998 there were 26 million Americans asthmatics, 10.6 of whom had had an attack during the past year. About a third of all asthmatics are children under 18. Since asthma is often undiagnosed, these statistics probably under-estimate the true prevalence of the disease.

Description

The lungs of asthmatics are hypersensitive to stimuli that do not affect healthy lungs. Many patients with asthma react to allergens such as pollen, dust mites, or animal dander, but colds, viruses, and environmental irritants such as dust and pollution can also be triggers.

During an asthma attack, cells in the bronchial walls called mast cells release chemicals that force the bronchial muscle to contract in spasms These chemicals, which include histamine, acetylcholine, and a group of substances called leukotrienes, also bring white blood cells into the area, which is a key part of the inflammatory response. This process also stimulates mucus formation. The entire process creates bronchoconstriction, making it difficult for the asthmatic person to breathe.

Asthma usually begins in childhood or adolescence, but it also may first appear in adulthood. While the symptoms may be similar, certain important aspects of asthma are different in children and adults.

Child-onset asthma

When asthma begins in childhood, it often does so in an atopic child, one who is genetically predisposed to become sensitized to allergens in the environment. Atopy is present in at least one-third and as many as half of the general population. When these children are exposed to dust mites, animal proteins, fungi, or other potential allergens, they produce a type of antibody intended to engulf and destroy the foreign materials. This sensitizes the airway cells to particular allergens. Further exposure can lead rapidly to an asthmatic response.

Adult-onset asthma

Allergies may also play a role in adult-onset asthma, which can start at any age and in a wide variety of situations. Adults may begin to react to allergens such as pollen, dust mites, and pet dander; they may find themselves allergic to aspirin and other drugs; and can even trigger an asthma attack with exercise. Another major cause of adult asthma is occupational exposure (and sensitization) to animal products, certain forms of plastic, wood dust, or metals. In addition, many people have such conditions as sinusitis or nasal polyps that also make them prone to asthma attacks.

Causes and symptoms

In most cases, asthma is caused by inhaling an allergen that sets off the biochemical chain reaction, causing the tissue changes that lead to airway inflammation, bronchoconstriction, and wheezing. Since avoiding, or at least minimizing, exposure is the most effective way to treat asthma, it is vital to identify which allergen or irritant is causing symptoms in each patient. Once asthma is present, symptoms can be triggered or made worse if the patient also has rhinitis (a cold or cold-like symptoms caused by allergies), sinusitis (inflammation or infection of the sinuses), or a viral infection of the respiratory tract (such as influenza). Gastroesophageal reflux disease (GERD), commonly referred to as acid reflux or heart-burn, can also make asthma worse. Some asthmatics are free of symptoms most of the time but may occasionally be short of breath. Others spend their days (and nights) coughing and wheezing, until properly treated.

Allergens and irritants most likely to cause asthma attacks are: smoke, animal dander, dust mites, fungi and molds, cockroach allergens, pollen, and industrial chemicals, fumes, or pollution. In addition, there are three conditions that can also provoke attacks in certain asthmatic patients: inhaling cold air, breathing hard during exercise, and stress or a high anxiety level.

During moderate to severe asthma attacks wheezing may be obvious, but mild attacks can be confirmed by listening to the patient's chest with a stethoscope. Wheezing is often loudest during exhalation, when the patient tries to expel air through narrowed airways. Besides wheezing and shortness of breath, the patient may also cough and report a feeling of tightness in the chest. Children may experience itching on their back or neck. Crying or even laughing may bring on an attack. Severe episodes often occur when patients contract viral respiratory tract infections or are exposed to heavy loads of an allergen or irritant. Asthma attacks may last only a few minutes or can persist for hours or even days (a condition called status asthmaticus).

Shortness of breath may cause a patient to become very anxious, sit upright, lean forward, and use the accessory muscles of respiration 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 indicate that the patient's oxygen supply is very low and emergency treatment is needed. If a severe attack lasts for some time, air sacs in the lung may rupture, trapping air within the chest. This makes it even harder to breathe in enough air. Fortunately, even patients with the most severe attacks usually recover completely.