RESPIRATORY-RELATED PHARYNGEAL CONSTRICTOR MUSCLE-ACTIVITY IN NORMAL HUMAN ADULTS

Electromyographic activity of the superior, middle, and inferior phary ngeal constrictor (PC) muscles was examined in 10 normal adult humans during wakefulness and sleep. Wire electrodes were inserted close to t he midline of the posterior pharyngeal wall at the level of the soft p alate (superior PC), tip of the epiglottis (middle PC), and corniculat e tubercle (inferior PC). In general, the three PC muscles exhibited s imilar patterns of activation. The PCs were activated during swallows, repetitive ''pa'' sounds, changes in head position, and the last port ions of slow inspiratory and expiratory vital capacity maneuvers. Resp iratory-related PC activity was infrequent during quiet breathing duri ng wakefulness; variable and inconsistent phasic activation in expirat ion in one or more of the PCs was present in seven of the 10 subjects, particularly after a swallow. Progressive hyperoxic hypercapnia and p rogressive isocapnic hypoxia were associated with recruitment of phasi c PC activity, which was predominantly expiratory; however, variable d ischarge patterns were observed within a given muscle and a given subj ect. When phasic PC activity was present, preactivation during late in spiration was frequently observed. PC activity was absent in NREM slee p and exhibited sporadic, nonrespiratory-related bursts of activity du ring REM sleep. Passively induced hypocapnic hyperventilation in NREM sleep was not associated with PC activation. The results indicate that the PCs have very similar patterns of activation and exhibit phasic e xpiratory activity during relatively high ventilatory output states in wakefulness.