Vagal stimulation for reciprocal coupling between glottic and upper esophageal sphincter activities in the canine

Glottic adduction couples with relaxation of the tonically contracted upper esophageal sphincter (UES) to constitute the end point of pharyngeal swall owing. Together with deglutitive laryngeal elevation, this reciprocal relat ionship contributes to protecting the lungs from aspiration. Degrees of unc oordination between glottic and upper esophageal sphincters can be seen und er diverse circumstances of neurologic damage such as stroke, gastroesophag eal reflux, and in the growing elderly population presenting with weaker mu sculature. We hypothesized that reciprocal coupling between glottic closure and UES relaxation may be artificially reestablished through vagal stimula tion if the appropriate neural centers and their leading pathways remain ca pable of exciting a critical number of motor units. Orderly recruitment of the vagus nerve was produced in three dogs with a circuit superimposing 600 -Hz, 3800-0-mu A blocking over 10-70-Hz, 0-2300-mu A stimulating currents. Amplitudes of motor unit or compound muscle action potentials were recorded from the thyroarytenoideus and cricopharyngeus via surface electromyograph ic electrodes. Stimulation was accompanied by a drop in UES intraluminal pr essure. The reciprocal relationship between the two muscles could be time l ocked within certain stimulus parameters. We submit that electronic couplin g between the glottic and UESs may show promise in preventing aspiration un der selected circumstances.