P1 A Novel Capsaicin Cough Challenge In Healthy Adults; Beyond The C5

Abstract

Introduction We have developed a novel cough challenge methodology and previously showed that evoked maximal cough responses, defined as E max , better discriminate health from disease than traditional endpoints. 1 It is unclear how other factors influence E max or how it relates to the low cough rates observed in health. We therefore aimed to investigate the variability, repeatability and influences on E max in a larger group of healthy volunteers. Objective To assess maximum cough responses to capsaicin in a group of healthy adults representing a wide range of ages. Method Doubling doses of capsaicin 0.49 to 1000[micro]M) were inhaled sequentially up to the maximum tolerated dose. Four inhalations of each dose were administered 30 seconds apart and the number of coughs evoked within 15 seconds was recorded. The maximum number of coughs evoked by any dose of capsaicin (E max ) and the dose that elicited half of the E max , defined as ED 50 , were calculated. General linear models were used to assess the influence of subject demographics on these endpoints. Results Forty seven healthy volunteers performed the capsaicin challenge; median age 38 years (range 20–74), 17 males, median FEV 1 103% predicted (97–115), median BMI 25.0 (22.2–28.6), and median total cough rate 0.2 c/h (0.0–0.1). The median E max was 11 coughs (IQR, 8–19) with an ED 50 of 15.6[micro]M (7.8–109.4). The intraclass correlation coefficients for E max and ED 50 were 0.89 and 0.96 respectively which were highly significant (p 1 and BMI had no significant influence on E max . In contrast, gender (p 50 explaining 41.7% of the variation. Those subjects with a higher BMI and females tended to have a lower ED 50 . Objective 24 h cough frequency did not correlate with either E max or ED 50 . Conclusion Data collected to date has demonstrated that in healthy volunteers, E max and ED 50 are stable measures over time however E max has the advantage of being independent of patient factors. Intere stingly, objective cough frequency in healthy volunteers seems to be unrelated to capsaicin evoked coughing. References J Allergy Clin Immunol . 2013 Oct;132(4):847–55