Effect of tartaric acid-induced cough on pulmonary function in normal and asthmatic humans.

Objective: The laryngeal cough reflex and the laryngeal cough expiratory reflex are brainstem reflexes that protect the upper airway from significant aspiration. The purpose of this investigation was to examine the effects of tartaric acid-induced cough on pulmonary function in normal healthy and asthmatic individuals.

Design: Twenty healthy and 20 asymptomatic, medicated, asthmatic volunteers engaged in a two-part evaluation of pulmonary function testing. All 40 subjects were nonsmokers. The reflex cough test, a 20% solution of prescription-grade L-tartaric acid dissolved in 0.15 M NaCl solution, initiated the laryngeal cough expiratory reflex/laryngeal cough reflex. The solution was placed in a Bennett Twin nebulizer and inhaled as a microaerosol. Pulmonary function testing was with a Spiromate AS-600. Baseline pulmonary function testing was initially performed, followed by two separate inhalations of the reflex cough test. The pulmonary function testing was repeated 5 min after the second reflex cough test.

Results: Statistically significant changes seen after the reflex cough test included increases in the peak inspiratory flow in normal subjects (P = 0.004) and in the peak expiratory flow in asthmatic subjects (P = 0.014). No respiratory adverse events occurred after the reflex cough test.

Conclusions: Explanations for these findings include the possibility that tartaric acid-induced cough produces central nervous system-mediated bronchodilatation, through the cough itself or by secondary mechanisms.