In this study, impulses of the medullary respiratory neurons, electromyogram of the diaphragm and subglottic pressure during the second stage of deglutition in felines, were recorded simultaneously. Strength of the glottic closure and intraluminal pressure of the cervical esophagus during deglutition were measured using a microtip transducer before and after tracheostomy. Activities of the respiratory neurons, contraction of the diaphragm and subglottic pressure change were highly constant in each deglutition. The decrease in strength of the glottic closure and disappearance of the falling of intraesophageal pressure were observed after tracheostomy. The results suggest that part of the respiratory neurons are driven by a preprogrammed command from the swallowing center and regulate respiratory muscles which elicite intrathoracic and subglottic pressure changes during the second stage of deglutition. Tracheostomy may disturb glottic closure and propelling of the bolus from the hypopharynx to the esophagus and is likely to cause aspiration.
