Respiratory-related pharyngeal constrictor muscle activity in normal human adults.

Electromyographic activity of the superior, middle, and inferior pharyngeal constrictor (PC) muscles was examined in 10 normal adult humans during wakefulness and sleep. Wire electrodes were inserted close to the midline of the posterior pharyngeal wall at the level of the soft palate (superior PC), tip of the epiglottis (middle PC), and corniculate tubercle (inferior PC). In general, the three PC muscles exhibited similar patterns of activation. The PCs were activated during swallows, repetitive "pa" sounds, changes in head position, and the last portions of slow inspiratory and expiratory vital capacity maneuvers. Respiratory-related PC activity was infrequent during quiet breathing during wakefulness; variable and inconsistent phasic activation in expiration in one or more of the PCs was present in seven of the 10 subjects, particularly after a swallow. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia were associated with recruitment of phasic PC activity, which was predominantly exp...