Λεξικό .. Asthma

(See asthma definitions of). Asthma prevalence rates increased by 75% in the Unites States between 1980 and 1994 [1]. The prevalence of allergic diseases is even higher in children [2], where asthma is the most common chronic illness overall. Twenty-three percent of British children aged 6-7years, and 21% of British children aged 12-14years [3] suffer from asthma. Despite better understanding of pathophysiology and improved treatment protocols for allergic diseases, overall morbidity and and even mortality rates of asthma have increased in the last two decades [4]. The predominant clinical features of asthma are breathlessness and wheeze, which are easily recognized, but there have been many disputes about the definition of asthma. In some patients, cough, with or without the production of tenacious sputum, may occur. Asthma can be defined as a disease(s) characterized by large changes in bronchial airflow resistance within relatively short periods of time [5].

This definition ignored the still largely uknown etiology and focuses on the one characteristic which is common to all forms of asthma, namely variable airflow obstruction. The extent to which the airway diameter changes and the duration of airway obstruction cannot be readily encompassed in a definition. These factors differ considerably in various patients and, even in the same patient, may show considerable differences depending on age, external stimuli and still poorly understood, endogenous factors. Frequently, if the condition has been present for a long time, it may change from periods of episodic breathlessness alternating with relatively symptom free intervals into a stage of the disease characterized by persistent symptoms as well as increasing and more or less irreversible airflow obstructio [6].  The symptoms of asthma are the result of bronchospasm, bronchial wall edema, and hypersecretion of mucous glands. The episodes of asthma can be continuous or paroxysmal, and may result in an impairment of respiratory function ranging from a modest degree of disability to lifge-threatening asphyxiation-status asthmaticus.

Asthma usually is reversible, either spontaneously or through treatment.Clinically, patients with asthma have one of several forms of the disease. The classification used is based mainly on known etiologic factors but also considers clinical variations. The combined etiologic-clinical classification is not entirely satisfactory, but in spite of that, it has the advantage of aiding the clinician in selecting appropriate therapy for the management of patients. It has been common practice to divide asthma into extrinsic, intrinsic, mixed asthma, status asthmaticus.

The two principal forms of asthma (extrinsic and intrinsic) have essentially similar pathologic and physiologic features. Patients with either form may have relatively symptom-free periods interrupted by paroxysms of acute airway obstruction which may progress to status asthmaticus. The clinical course of asthma is variable so that patients often cannot be unequivocally classified as having the extrinsic or intrinsic type. For instance, mixed asthma has features common to both forms of the disease. Either type of asthma may become chronic, or infective bronchitis and even  emphysema may coexist with the asthma and worsen the prognosis. Thus, a number of clinical subtypes of asthma exist such as: Chronic asthmatic Bronchitis, Aspirin Sensitivity asthma, and nasal polyposis, Exercise induced Asthma, dual Type I and Type II reactions and chronic Asthma.

References

1. Doyle R. Asthma worldwide. Sci Am 2000;282:30.

Mitchell EA. Asthma epidemiology: clues and puzzles. Pediatr Pulmonol Suppl 1999;18:31-33.

2. Burney PG. Asthma. Epidemiology. Br Med Bull. 1992 Jan;48(1):10-22

3. . Asthma epidemiology: clues and puzzles. Pediatr Pulmonol Suppl. 1999;18:31-3

4. Woolcock AJ. Learning from asthma deaths. BMJ 1997;314:1427-1428.

5. Scadding, J.G.: Definition and clinical categories of asthma. In Asthma (Eds TJH Clark and S. Godfrey. Chapman and Hall, London, pp. 1-11.). (1983).

6. Morgenroth, K. Wettengel R., Newhouse M.: Bronchial Asthma. Boehringer Ingelheim. Int. GmbH. 1987.