In asthma, wheezing and dyspnea are most directly due to which pathophysiological feature?

• A. Inflammation and edema of the pleura
• B. Narrowing of the airway
• C. Blockage of the pulmonary arteries
• D. Infection of the bronchial mucosa

Answer: (B)

Wheezing and dyspnea in asthma come from the airways becoming narrowed. During an asthma attack, inflammatory mediators cause the smooth muscle around the bronchi to contract (bronchoconstriction) and the airway walls to swell with edema, with mucus potentially plugging the lumen. This reduces airway caliber, which greatly increases resistance to airflow, especially during expiration, producing the characteristic wheeze and the difficulty breathing.

Other processes don’t directly produce this pattern. Inflammation of the pleura would more likely cause chest pain with breathing. Blockage of the pulmonary arteries would present differently, often with sudden shortness of breath and signs of venous congestion rather than the wheeze. Infection of the bronchial mucosa can cause cough and sputum but isn’t the primary reason for the episodic airway narrowing that leads to wheeze in asthma.