الفهرس 
INTRODUCTION & AIM OF WORKOnly 14 pages are availabe for public view
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Abstract
In 1991, The National Asthma Education Program Expert Panel Report from the National Institutes of Health defined asthma as a lung disease with the following characteristics: (1)- airway obstruction that is reversible, either spontaneously or with treatment; (2)- airway inflammation; and (3)- increased airway responsiveness to a variety of stimuli It is likely that asthma is not a specific disease, but a syndrome that derives from multiple precipitating mechanisms and results in a common clinical complex involving airway obstruction (Snapper, 1990). The patient who has symptoms consistent with asthma but has normal pulmonary function test results, bronchoprovocation testing remains the only way to make a positive diagnosis of asthma in this setting, since lung function is normal and there is no response to a bronchodilator. This situation is common in mild or well-managed asthma (Goldstein, et. al., 1994) The principal methods of eliciting hyperresponsiveness involve challenge with a pharmacologic agent, exercise, food, or an allergen. Exercise-induced bronchoconstriction occurs in 70 to 80 percent of patients with current symptomatic asthma (McFadden and Gilbert 1994). The magnitude of exercise-induced bronchoconstriction is correlated with the degree of airway hyperresponsiveness (Anderson, 1989). Therefore, in many patients with mild, episodic asthma and only mildly increased airway responsiveness, even strenuous exercise does not cause bronchoconstriction. After sufficient exercise most asthmatic patients develop exercise-induced asthma (Godfrey, et. al., 1992). Exercise-induced asthma is often a problem in children and in adults involved in physical sports and may be the sole symptoms in some patients with mild asthma. The maximum degree of bronchoconstriction occurs usually about 5-10 min after the cessation of exercise and symptoms subside within 15-30 min. There is often a refractory period of around 2hours after the development of exercise-induced asthma. During this period repeated exercise dose not cause bronchospasm (Anderson, 1989).The aim of this work was to compare methacholine and exercise challenge tests as diagnostic tools of bronchial hyperreactivity in bronchial asthma.