The examination of the posterior cricoarytenoid muscle activity during respiration in human subjects.

Eight healthy human subjects were studied to examine the posterior cricoarytenoid (PCA) muscle activity during respiration. A hypopharyngeal surface electrode was used for posterior cricoarytenoid (PCA) muscle recordings. Mean activation levels were derived from rectified signals (in muV) for quartiles of each respiratory cycle: the first and second halves of the inhalation, and the first and second halves of the exhalation. The mean activation was converted into the % of maximum activity for the same muscle during deep inhalation to normalize the measures of muscle activation across subjects. On a two way ANOVA, respiratory interval effect (P less than 0.0001), subject effect (p less than 0.0001), and interval by subject interaction (p less than 0.0014) were significant. The muscle activation increased in abductory (PCA) muscles during inhalation. However PCA kept active during exhalation in certain degree. Significant difference in PCA activity among subjects was found. Using the sliding window average over 100 msec time constant, PCA activation pattern during respiration was classified into 4 categories: phasic activity during exhalation, phasic activity during inhalation and exhalation, and non phasic activity unrelated to the respiratory cycle. The classification was carried out in 8 subjects. 5 out of 8 subjects revealed phasic inhalation pattern (62.5%) and 3 subjects showed non-specific phasic activity. Big difference among subjects in activation level and activation pattern of the PCA was suggested.