Cough Receptor Sensitivity and Bronchial Responsiveness in Patients with Only Chronic Nonproductive Cough: In View of Effect of Bronchodilator Therapy

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Abstract
Twenty-two patients with only chronic nonproductive cough lasting for more than 2 months were prospectively examined to determine whether airway cough receptor sensitivity and bronchial responsiveness relate to the efficacy of bronchodilator therapy on the cough. Clenbuterol (10 micrograms, 4 times a day for 1 week) was effective on the cough in 10 patients (group 2) but not in the other 12 patients (group 1). Cough threshold to inhaled capsaicin was significantly less in group 1 than in group 2 at the first visit but not after the therapy when the cough stopped. Bronchial responsiveness to methacholine (PC20-FEV1) was not heightened in group 1, while that in group 2 was hyperreactive. These findings suggest that nonproductive cough is elicited based on two different mechanisms: (1) heightened airway cough receptor sensitivity in bronchodilator-resistant cough and (2) bronchoconstriction in bronchodilator-responsive cough such as cough-variant asthma.