Effect of chronic and acute cigarette smoking on the pharyngo-upper oesophageal sphincter contractile reflex and reflexive pharyngeal swallow

Background-Cigarette smoking is known to affect adversely the defence mechanisms against gastro-oesophageal reflux. The effect of smoking on the supraoesophageal reflexes that prevent aspiration of gastric contents has not been previously studied. Aims-To elucidate the effect of cigarette smoking on two of the supraoesophageal reflexes: the pharyngo-upper oesophageal sphincter (UOS) contractile reflex; and the reflexive pharyngeal swallow. Methods-Ten chronic smokers and 10 non-smokers were studied, before and 10 minutes after real or simulated smoking, respectively. UOS pressure and threshold volume for the reflexes were determined using a UOS sleeve assembly. Two modes of fluid delivery into the pharynx were tested: rapid injection and slow injection. Results-For both rapid and slow injections, the threshold volume for triggering the pharyngo-UOS contractile reflex was significantly higher in smokers than in non-smokers (rapid: smokers 0.42 (SE 0.07) mi, non-smokers 0.16 (0.04) mi; slow: smokers 0.86 (0.06) mi, non-smokers 0.38 (0.1) mi; p<0.05). During rapid injection, the threshold volume fbr reflexive pharyngeal swallow was higher in smokers (smokers 0.94 (0.09) mi, non-smokers 0.46 (0.05) mi; p<0.05). Acute smoking further increased the threshold volume for the pharyngo-UOS contractile reflex and reflexive pharyngeal swallow during rapid injection. Conclusions-Smoking adversely affects stimulation of the pharyngo-UOS contractile reflex and pharyngeal reflexive swallow. These findings may have implications in the development of reflux related respiratory complications among smokers.