CAPSAICIN COUGH RECEPTOR SENSITIVITY TEST IN CHILDREN

Capsaicin has been used as a tussive agent in studies in adults to det ermine cough receptor sensitivity, The aim of this study was to determ ine the tolerance, repeatability and influence of inspiratory flow on the capsaicin cough receptor sensitivity test in children. Thirty chil dren (mean age 11 yrs; range 6-16 yrs) were tested on two different da ys, to determine the lowest concentration of capsaicin required to sti mulate two or more coughs (cough threshold (Cth)), 2-4 coughs (C2), an d five or more coughs (C5), Capsaicin was nebulized through a dosimete r, with an arrangement that allowed the subjects to visualize and regu late their inspiratory flow. Using a constant inspiratory flow of 20 L . min(-1), tests were reproducible for C2, C5 and Cth (doubling dose changes of 1.13, 1.03 and 1.08, respectively). An increase children in the inspiratory flow from 20 to 60 L . min(-1) significantly increase d C2 (19.5 to cough 46.8 mu M; p=0.016) and C5 (46.8 to 128.8 mu M; p= 0.008). We conclude that in children, the capsaicin cough challenge te st: 1) is well-tolerated; 2) is highly repeatable; and that 3) the ins piratory flow significantly influences cough receptor sensitivity and repeatability of the test and should, thus, be regulated.