Official websites use. Share sensitive information only on official, secure websites. Corresponding author D. Email: david. During swallowing, the airway is protected from aspiration of ingested material by brief closure of the larynx and cessation of breathing. Mechanoreceptors innervated by the internal branch of the superior laryngeal nerve ISLN are activated by swallowing, and connect to central neurones that generate swallowing, laryngeal closure and respiratory rhythm.
This study was designed to evaluate the hypothesis that the ISLN afferent signal is necessary for normal deglutition and airway protection in humans. In 21 healthy adults, we recorded submental electromyograms, videofluoroscopic images of the upper airway, oronasal airflow and respiratory inductance plethysmography.
In six subjects we also recorded pressures in the hypopharynx and upper oesophagus. We analysed swallows that followed a brief infusion 4β5 ml of liquid barium onto the tongue, or a sip 1β18 ml from a cup. In 16 subjects, the ISLN was anaesthetised by transcutaneous injection of bupivacaine into the paraglottic compartment.
Saline injections using the identical procedure were performed in six subjects. Endoscopy was used to evaluate upper airway anatomy, to confirm ISLN anaesthesia, and to visualise vocal cord movement and laryngeal closure. Comparisons of swallowing and breathing were made within subjects anaesthetic or saline injection vs. In the non-anaesthetised condition saline injection, swallows in six subjects; no injection, swallows in 20 subjects , laryngeal penetration during swallowing was rare 1.
During ISLN anaesthesia 16 subjects, swallows , all subjects experienced effortful swallowing and an illusory globus sensation in the throat, and 15 subjects exhibited penetration of fluid into the larynx during swallowing. We further analysed the swallow cycle to evaluate the mechanism s by which fluid entered the larynx. Laryngeal penetration was not caused by premature spillage of oral fluid into the hypopharynx, delayed clearance of fluid from the hypopharynx, or excessive hypopharyngeal pressure generated by swallowing.
