Definition of Allergy
Allergy is an immunologic reaction to an otherwise innocuous material that doesn't bother most people. The term immunologic is the most important word. The allergic person's immune recognizes as something as foreign and mounts a very specific approach that is designed to identify the foreign "allergen" so it can be destroyed with inflammation. Therefore, a unusual sensitivity to a material that brings out an unpleasant symptom is only allergic if it has an identifiable mechanism. This distinction between allergic and nonallergic illnesses is very important because it determines evaluation and treatment. Treatment of an allergic problem as if it is nonallergic will fail and visa versa.
Bronchial Asthma
By D.Robert Webb, M.D.
Introduction
Asthma is a common lung problem that effects about five percent of the population, occurs at all ages, and has had major changes in understanding and treatment in the last decade. The major change in understanding is realization that asthma is a bronchial inflammatory disease. It appears that inflammation is the cause of symptoms of wheezing, shortness of breath, and mucous production which have been known since the classical Greek period 3,000 years ago. The importance of inflammation has led to the changes in treatment discussed below.
Definition
Bronchial asthma is a lung disease in which the bronchial tubes are hypersensitive to many different irritants including viral infections, air pollution, excercise, allergens and various fumes. The reaction to these irritants has long been recognized as narrowing of these small airways and increased mucous secretions. This gives characteristic variability of lung function with obstruction on exhaling that is easily measurable in the medical office and at the patient's home.
Anatomy and Mechanism of Asthma
The air-conducting tubes in the lungs carry the air from the upper airway and trachea (major windpipe in the neck) through approximately 10 branches before reaching the air sacs (alveoli) that bring the air in intimate close contact with tiny blood vessels where exchange of oxygen and carbon dioxide can occur between air and blood. The circulation then transfers oxygen rich blood to the tissues where it diffuses by simple concentration gradients into the tissues. In the meantime, waste carbon dioxide diffuses back into the blood in these tiny blood vessels (capillaries) to be returned for removal by the lungs. These small air tubes called bronchi and bronchioles are the location of problems in the asthma sufferer. Because of irritated membranes in these little tubes, reflexes make smooth muscle surrounding the air tubes contract, narrowing the airways. Other reflexes stimulate normal glands in the bronchi to secrete extra mucous thus narrowing the openings further. Of particular concern is the likelihood that continual inflammation of the bronchi may result in permanent scarring of the little tubes so they are permanently narrowed and thus not able to ever transport air to the alveoli normally.
Cause of Asthma
Understanding of the cause or pathogenesis of asthma underwent a major change in the late 1980s. Before that time the symptoms of wheezing, shortness of breath, and mucous production were well recognized in patients of all ages, and we knew that many triggers seemed to start an asthma attack. However, why most normal people don't react with the characteristic symptoms and asthma sufferers do was unknown. Peter Barnes and other investigators, aided by newer techniques of fiberoptic bronchoscopy and harvesting cells from the lungs by washing, recognized the mucous membrane layer of the bronchial tubes was damaged, even in patients whose asthma was very mild. Although these inflammatory changes had been recognized in severe asthma with fatal outcome, they were not previously recognized as being a primary finding in all asthma even when it was very mild.
There are multiple triggering stimuli that will increase symptoms. Best known is allergy, but cold air, excercise, viral infection, air pollution, and industrial exposures commonly cause asthma symptoms. The common factor seems to be an irritation of the respiratory mucous membrane. Since asthma is so common and since relatively few sufferers are maimed or die, many feel asthma is not really very serious. Increasing inflammation can cause cascading inflammatory consequences resulting in respiratory failure and death. About five thousand people die annually in the United States from asthma. Of particular concern is an increase in frequency of asthma. Contamination of environmentally "tight" (damper) households with increased house dust mite infestation, and the recognition that asthma occurs in adults of all ages are responsible for some of this increased frequency.
Allergy in Asthma
For many years allergy to seasonal pollens, animal danders, and house dust were the most recognized precipitating influences associated with attacks of asthma. There is a common misconception that allergy and asthma have the same meaning. This is an important misconception to overcome. Allergy is one of several triggers of asthma, but the basic inflammatory condition is the integral factor of asthma and is often not directly caused from an allergic reaction. On the other hand, allergy is an extremely common trigger of asthma flares, particularly in children and young adults.
Treatment
Treatment of asthma has always started with eliminating triggers so far as possible. These triggers are different for each person and understanding of the individual patterns of each individual is very important. Careful environmental evaluation is necessary to determine whether allergy, infection, industrial exposure, excercise and other influences are important in the individual patient. Any approach to these inciting agents brings important benefits in asthma patients who can ameliorate symptoms very commonly by simply avoiding certain allergens. This remains a very important factor even when the inflammatory condition is suppressed with other therapy such as very effective inhaled steroid (cortisone) medication. The recognition that hyperirritable airway was inflamed has lead to a new approach to medication. For generations bronchodilators were the first and most effective treatment to control flares of asthma symptoms. Although this is still true, the better approach has become clear over the last decade. It is rare for an asthma sufferer to be hospitalized , seriously ill, or even require an emergency room visit once antiinflamatory agents are used prophylactically to control pulmonary inflammation. This not only allows the asthma patient a control over their asthma they have never previously known, but it is a much less expensive treatment than previously frequent emergency management. The basis for treatment is now using regular antiinflamatory therapy as first line therapy for any patients who have more than occasional symptoms. The bronchodilators are still used but only when the control given by antiinflamatory therapy is inadequate and then in much smaller amounts.
Conclusion
Bronchial asthma is a common illness of the lungs affecting about five percent of the population. It has increased in frequency and in mortality for reasons that are not clear. New knowledge of the importance of inflammation in asthma has lead to newer more effective treatment. There is no reason for this illness to have fatal outcomes or require expensive hospital care. Unfortunately many asthma patients don't have access to health care providers and have missed out on these wonderful developments. Once the patient recognizes that he or she can self manage asthma effectively with only occasional help in the office by their doctor, a major improvement in health and quality of life always follows.
Recommendations
Any individual who has recurring intermittent shortness of breath, wheezing, cough or bronchitis should ask his or her care giver whether this may be caused by asthma. If this is possible he should request tests of breathing function and possible tests for allergy to confirm or rule out this easily treatable problem.
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