Bronchoconstriction

Bronchoconstriction refers to the narrowing of the airways caused by constriction of the bronchial smooth muscle. It results in reduced airway caliber and airflow resistance that can range from mild to life-threatening. It is a key feature of asthma and can occur in several other conditions.

Pathophysiology involves airway inflammation with release of mediators from mast cells, eosinophils, and other inflammatory cells, including histamine, leukotrienes, and prostaglandins. Parasympathetic stimulation and acetylcholine contribute to smooth muscle contraction. Edema of the airway wall and mucus production further obstruct the lumen, promoting hyperresponsiveness.

Common triggers include asthma, chronic obstructive pulmonary disease, allergic reactions, viral infections, exercise, cold air, and exposure to irritants. Exercise-induced bronchoconstriction is a specific form that occurs during or after physical exertion. Acute severe episodes may require urgent assessment.

Diagnosis relies on clinical features and objective lung function testing. Spirometry typically shows reduced FEV1 and decreased FEV1/FVC with partial or full reversibility after bronchodilator administration. Peak expiratory flow rate monitoring can aid in outpatient assessment.

Management aims to relieve symptoms, prevent episodes, and treat underlying disease. Acute relief is achieved with inhaled short-acting beta-agonists; anticholinergics and systemic steroids may be used in moderate to severe cases. Long-term control includes inhaled corticosteroids, other anti-inflammatory agents, trigger avoidance, and patient education. Prognosis depends on the underlying condition and adherence to therapy.