Effect of chronic and acute cigarette smoking on the pharyngoglottal closure reflex

Background: Injection of water into the pharynx at a threshold volume induces vocal cord adduction - the pharyngoglottal closure reflex (PGCR). This reflex together with other supraoesophageal reflexes may be helpful in preventing aspiration. Cigarette smoking has an adverse affect on the pharyngo-upper oesophageal sphincter contractile reflex and reflexive pharyngeal swallow. The effect of smoking on PGCR has not been studied previously. Aims: To elucidate the effect of chronic and acute cigarette smoking on PGCR. Subjects: We studied 10 chronic smokers and 10 non-smokers before and after real/simulated smoking, respectively. Methods: Using concurrent recordings, glottal function was monitored by video endoscopy, swallowing by electromyography, and PGCR was triggered by rapid and slow pharyngeal water injections. Results: The threshold volume to trigger PGCR during rapid injection was significantly higher in chronic smokers (non-smoker 0.20 (SEM 0.02) ml, smoker 0.36 (0.02) ml; p<0.001). In six of 10 smokers, acute smoking abolished this reflex during slow water injection. Conclusions: Smoking adversely affects stimulation of PGCR. This finding may have implications in the development of reflux related respiratory complications in smokers.