There is currently interest in the association between gastroesophageal reflux disease (GERD) and asthma. In one study, acid reflux on the distal but not the proximal esophagus correlated with chronic persistent cough. The researchers of that study believed this to be a result of acid that stimulated inflamed distal esophageal mucosal receptors, resulting in a reflux-mediated cough. The effect of GERD on cough responsiveness in patients with asthma has not been established. Wu and colleagues studied the effect of distal esophageal acid perfusion on cough responsiveness in patients with bronchial asthma even if there was no evidence of esophagitis.

Seven patients with mild, persistent bronchial asthma but no symptoms of GERD were enrolled in the study. Esophageal pH was monitored by an esophageal pH meter, and cough responsiveness was determined by a single-breath aerosol inhalation of capsaicin with increasing doses. Simultaneously, esophageal perfusion was carried out through an esophageal tube filled with either 0.1 N hydrochloric acid (HCl) or saline solution in a randomized fashion at one-week intervals. Positive results were expressed as the lowest dose of capsaicin that would produce three coughs. Spirometry also was performed during the esophageal pH monitoring.

The results showed a significant decrease in the dose of capsaicin that would produce cough in asthmatic patients who received HCl acid infusions in the distal esophagus compared with saline infusions. There were no significant changes in spirometry results between the infusion of HCl acid and saline.

The authors conclude that cough responsiveness may be induced when the distal esophagus is stimulated with HCl acid in patients with bronchial asthma. They add that GERD might be one of the most important factors influencing asthma status.