Comparisons of cough reflex sensitivity during various external vibrations. (A) Dose–response relationship of cough counts as a function of citric acid concentrations. Data are mean ±standard errors (SE). The comparisons among curves were performed using two-way repeated ANOVA with Fisher’s PLSD. *p<0.01, †p<0.05. The comparison between curves not indicating any symbol means no significant difference. (B) Cough reflex sensitivities are expressed as the log transformation of the lowest concentration of citric acid that elicited five or more coughs (C5). Closed circles and error bars indicate the mean value and SE in each group, respectively. P value indicated were calculated by one-way ANOVA with Fisher’s PLSD post hoc. Comparisons between the groups not indicating p value mean no significance.