CRICOTHYROID MUSCLE-ACTIVITY DURING SLEEP IN NORMAL ADULT HUMANS

Previous investigators reported that cricothyroid (CT) muscle usually exhibits phasic inspiratory activity in normal adult humans during wak efulness. The purpose of this study was to determine respiratory-relat ed CT activity in normal adult humans during sleep. Nighttime polysomn ograms were performed in 16 subjects. Hooked-wire electrodes were perc utaneously implanted in CT with 21-gauge needle-catheter unit that all owed artifact-free monopolar recordings during electrode placement. Du ring wakefulness, CT was usually phasically active on inspiration, wit h tonic activity throughout the respiratory cycle. Phasic inspiratory activity was present throughout sleep in all subjects, even those with out respiratory-related CT activity during wakefulness. Compared with non-rapid-eye-movement (NREM) sleep, phasic CT activity uniformly incr eased in rapid-eye-movement (REM) sleep. No differences were apparent in height of phasic CT activity between phasic and tonic REM sleep. Ap plication of nasal continuous positive pressure in stage 3/4 NREM slee p was associated with a decrease in phasic CT activity. Passively indu ced hypocapnia with positive-pressure ventilation via a nose mask in s tage 3/4 NREM sleep was associated with a disappearance of phasic CT a ctivity. Cessation of positive-pres- sure ventilation under hypocapnic conditions frequently resulted in apnea. Phasic CT activity remained absent during apnea but reappeared coincident with or soon after resum ption of spontaneous respiration. In summary, CT's phasic inspiratory activity and respiratory-related response to various stimuli during sl eep were very similar to those of posterior cricoarytenoid muscle, the principal vocal cord abductor.