Airway hyperresponsiveness to a variety of stimuli. Pathophysiology Airway obstruction. Airway obstruction is responsible for the clinical manifestations of asthma such as wheezing, dyspnea, and cough. Airway narrowing may worsen gradually and persist despite therapy, but it can also develop abruptly and produce acute respiratory insufficiency. Airflow obstruction, which is determined by the diameter of the airway lumen, can be influenced by a number of factors, including edema of the bronchial wall, mucus production, airway smooth muscle contraction, and hypertrophy.
Airway obstruction is thought to be initiated by inflammatory events in the airways.
The airways of asthma patients are infiltrated by a number of different inflammatory cells, which then cause complex interactions resulting in epithelial disruption and mucosal edema. An initial trigger in asthma may cause the release of inflammatory mediators from bronchial mast cells, macrophages, and epithelial cells. These substances cause the directed migration and activation of an inflammatory infiltrate composed predominantly of eosinophils and neutrophils. Leukotrienes are released and attract further cellular infiltrate. This process produces epithelial injury, abnormalities in neural mechanisms, increases in airway smooth muscle responsiveness, and airflow obstructions.