The pathophysiology of asthma is characterized by a pattern of lung dysfunction that includes [1,2]:
●Airflow limitation that reverses with bronchodilator administration.
●Variable airflow limitation, which can be either circadian or episodic in nature.
●Airways hyperresponsiveness, which is an excessive decrease in airflow in response to specific stimuli or "triggers" (see "Risk factors for asthma").
Unlike other pulmonary diseases, asthma cannot be identified by a definitive pathologic picture or one diagnostic test. Rather, the diagnosis of asthma is based upon an appropriate clinical history and characteristic findings from a series of pulmonary function tests [1-4]. These tests most often include different measures of airflow, bronchodilator responses, lung volumes, and the diffusing capacity.