Bronchialhyperreagibilität

Bronchial hyperresponsiveness, also called bronchial hyperreactivity (BHR), describes an exaggerated constrictive response of the airways to stimuli that are usually tolerated. These stimuli can include pharmacologic provocatives such as methacholine or histamine, physical triggers like exercise, cold air, and airborne irritants. BHR is most commonly associated with asthma but can be present in other respiratory or allergic conditions.

In asthma and related diseases, BHR reflects underlying airway inflammation and remodeling. The process involves activated inflammatory cells (eg, eosinophils, mast cells, T helper 2–type lymphocytes), increased airway smooth muscle reactivity, and structural changes to the airway walls that amplify narrowing during exposure to triggers.

Assessment often uses bronchoprovocation testing. The methacholine challenge determines the concentration that causes a 20% drop in FEV1 (PC20). A lower PC20 indicates greater sensitivity. These tests support diagnosis and monitoring but are not entirely specific for asthma and must be interpreted alongside symptoms and lung function. Factors such as smoking, atopy, and current medications can influence results.

Management focuses on reducing airway inflammation and minimizing exposures. Inhaled corticosteroids are a common controller therapy that can lessen BHR over time; β2-agonist bronchodilators provide rapid relief of symptoms by reversing bronchoconstriction. Other options include leukotriene receptor antagonists, mast cell stabilizers, and lifestyle measures such as regular exercise and avoiding triggers. Clinically, improvement in asthma control generally correlates with reduced BHR.