Activity of the upper esophageal sphincter (UES) during eupnea, cough, and swallow

Abstract

Coordination of breathing, cough, and swallow is vital for airway protection. The upper esophageal sphincter (UES) is primarily composed of the cricopharyngeus muscle and is responsible for maintaining tone in the upper esophagus to restrict backflow. We hypothesized that the UES would alter its activity to coordinate the pharyngeal/esophageal junction during cough and swallow. Electromyograms (EMG) of the UES, geniohyoid (GH), thyroarytenoid (ThAr), parasternal, and abdominal muscles were recorded in anesthetized cats. Swallow was elicited by a water bolus in the pharynx, and cough was elicited by mechanical stimulation of the trachea. The UES EMG was tonically active during eupnea. During swallow the UES had a bi-phasic response, which first consisted of a period of decreased activity, followed by an EMG burst. During mechanical stimulation of the trachea, the UES EMG had increased activity, which was further increased during coughing. The UES activity during cough began in the inspiratory phase and spanned the first portion of the expiratory phase. Additionally, during repetitive coughing, in which there was a co-occurrence of swallow and cough, post-swallow coughs had significantly greater UES EMG amplitude compared to pre-swallow coughs. The results support a more complex coordinating mechanism between airway protective behaviors than previously appreciated. Supported by NIH HL 89104; HL 103415.