Investigation of the urge-to-cough sensation in healthy volunteers

Background and objective:  Recently, there has been interest in the sensation of irritation that precedes the motor act of coughing, which has been termed the urge-to-cough (UTC). The aim of this study was to perform the largest evaluation to date of the UTC threshold (Cu) in a healthy population. The specific aims were to investigate the relationship between Cu and cough reflex sensitivity, to evaluate gender differences in the UTC and to assess the reproducibility of measurements of Cu. Methods:  Standard capsaicin cough challenge methodology was employed to measure cough reflex sensitivity in 100 healthy adult non-smokers (50 females) with the additional measurement of Cu. A subgroup of 40 subjects (20 males) underwent repeat cough challenges after 1 week to examine the reproducibility of the measurements. Results:  All 100 subjects demonstrated motor cough in response to capsaicin. Twenty-one subjects (10 females) did not show a discernible Cu, as the motor cough event preceded a UTC sensation unaccompanied by cough. Although cough reflex sensitivity, as measured by the concentration of capsaicin inducing five or more coughs (C5), was enhanced in women, there was no gender difference in Cu. Similar to standard cough reflex sensitivity measurements, the measurement of Cu was highly reproducible. Conclusions:  These results demonstrate that the UTC threshold can be effectively and reproducibly measured using a modification of standard cough challenge methodology. Given its clinical significance as a prevalent symptom, UTC, as measured by Cu, represents an additional relevant end point for studies investigating the effects of pharmacological and other interventions in cough and cough reflex sensitivity.