Effect of Electronic Cigarette Use on the Urge-to-Cough Sensation.

INTRODUCTION: Electronic cigarettes (e-cigs) have attained common usage worldwide, yet knowledge of their physiological effects remains minimal. The aim of this study was to evaluate the effect of a single exposure to e-cig vapor on the urge-to-cough (UTC) threshold and C5.

METHODS: Seventeen healthy nonsmokers underwent C5 measurement employing capsaicin cough challenge at baseline, 15 minutes, and 24 hours after e-cig exposure (30 puffs 30 seconds apart). The endpoint of cough challenge is C5, the concentration of capsaicin inducing five or more coughs. The UTC threshold (Cu) is defined as the lowest concentration of capsaicin inducing UTC without an associated motor cough.

RESULTS: The Cu and C5 were significantly inhibited (Cu and C5 increased) 15 minutes after e-cig use. Mean log Cu rose from -0.035±0.08 (SEM) to 0.21±0.12 (P = .005). Mean log C5 increased from 0.60±0.11 to 0.92±0.16 (P = .001). By 24 hours after e-cig exposure, Cu and C5 had returned to baseline levels.

CONCLUSIONS: A single session of e-cig use, approximating nicotine exposure of one tobacco cigarette, induces significant inhibition of the Cu, as well as C5. Previous studies implicate nicotine as the agent responsible for suppression of C5, and we hypothesize a similar role for nicotine in the suppression of the Cu. Given our observation of the effect of a single e-cig exposure, studies of the respiratory physiologic implications of repeated or chronic e-cig use are warranted.

IMPLICATIONS: This is the first study to demonstrate that a single exposure to an e-cig significantly inhibits the Cu as measured by capsaicin cough challenge testing. These findings add to the growing body of evidence that e-cig vapor is not a physiologically benign substance, and support further investigation of the effects of repeated or chronic use of e-cigs on cough sensitivity and other respiratory parameters.