Am. J. Respir. Crit. Care Med., Vol 155, No. 6, 06 1997, 1991-1999.
Respiratory-related pharyngeal constrictor muscle activity in normal human adults
ST Kuna, JS Smickley and CR Vanoye
Department of Internal Medicine, The University of Texas Medical Branch, Galveston, USA.
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
expiratory; however, variable discharge patterns were observed within a
given muscle and a given subject. When phasic PC activity was present,
preactivation during late inspiration was frequently observed. PC activity
was absent in NREM sleep and exhibited sporadic, nonrespiratory-related
bursts of activity during 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 expiratory activity during relatively high ventilatory
output states in wakefulness.
