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

Abstract

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.

Figure 1

(A) Example of a pharyngoglottal closure reflex during rapid pharyngeal water injection. E, posterior aspect of the epiglottis; VC, vocal cords; A, arytenoids; P, posterior pharyngeal wall; M, manometry catheter; E1, E2, E3, perfusion ports 0, 7, and 14 cm below the upper oesophageal sphincter (UOS) sleeve, respectively; S, swallow; EMG, submental surface electromyography (EMG) recording. Video frame A: Vocal cord position immediately prior to rapid intrapharyngeal injection of water. Video frame B: Injection of 0.3 ml of water resulted in an abrupt complete closure of the vocal cords together with more than 100% increase in UOS pressure over baseline (pharyngo-UOS contractile reflex). Video frame C: Vocal cord partially abducted. Video frame D: Vocal cords returning to resting position 0.5 seconds after injection. These responses were not associated with any EMG activity of the submental muscles. Injection of 0.4 ml of water into the pharynx resulted in a reflexive pharyngeal swallow. (B) Example of pharyngoglottal closure reflex during slow pharyngeal water injection. Video frame A: Vocal cord position immediately prior to slow intrapharyngeal injection of water. Video frame B: Intrapharyngeal injection of water at the slow rate of 5.5 ml/min resulted in incomplete closure of the vocal cords together with more than 100% increase in UOS pressure over baseline. Video frame C: Vocal cord partially abducted. Similar to rapid water injection, these responses were not associated with any EMG activity of the submental muscles. Video frame D: Reflexive pharyngeal swallow was triggered 27 seconds after the onset of pharyngeal water perfusion.

Figure 2

Threshold volume (mean (SEM)) to trigger the pharyngoglottal closure reflex during rapid intrapharyngeal injection of water was significantly higher in chronic smokers compared with non-smokers. The threshold volume to trigger this reflex did not change significantly after acute smoking of two cigarettes.

Figure 3

Duration (latent period) in seconds (mean (SEM)) between onset of rapid intrapharyngeal water injection and onset of vocal cord adduction.

Figure 4

Slow intrapharyngeal injection of water triggered the pharyngoglottal closure reflex in all non-smokers. This reflex was absent in one smoker pre- and post-smoking (*) and smoking two cigarettes abolished this reflex in an additional six of the 10 smokers (†). Values are mean (SEM).

Figure 5

Duration (latent period) in seconds (mean (SEM)) between onset of slow intrapharyngeal water injection and onset of vocal cord adduction.