Effect of mucosal anaesthesia on oropharyngeal swallowing

The effect of the topical anaesthesia of the oropharyngeal mucosae was studied in order to evaluate the role of the mucosal sensory receptors on the oropharyngeal swallowing in 12 adult volunteers. Laryngeal vertical movements were detected by a piezoelectric sensor and electromyography of the submental muscle complex were simultaneously recorded. All subjects were instructed to swallow doses of water, gradually increasing in quantity from 3-20 mL and any recurrence of the signals related to swallowing within 8 s was accepted as a sign of dysphagia and its limit value measured. Before the topical anaesthesia of the oropharyngeal mucosae by xylocaine puffs; the dysphagia limit was never observed with less than 20 mL water. During topical mucosal anaesthesia lasting 4-6 min among the subjects, the dysphagia limit was less than 20 mL water and the recurrence of swallows two or more times was mainly recorded with 3-5 mL water. Five of the subjects demonstrated the clinical and electrophysiological signs of laryngeal aspiration at the earlier period of the topical anaesthesia. It is concluded that the sensory inputs from the mucosal receptors are important to trigger voluntary swallowing and their absence or dysfunction may contribute to oropharyngeal dysphagia and laryngeal aspiration.