Intramuscular and esophageal electrode recordings of posterior cricoarytenoid activity in normal subjects

Six normal human subjects were studied to compare intramuscular and esophageal electrode recordings of posterior cricoarytenoid (PCA) muscle activity. A new electromyographic technique was developed to implant hooked wire electrodes into the PCA via a nasopharyngoscope. The esophageal electrode was similar to that used by other investigators to record PCA activity (P. C. Kosch et al. J. Appl. Physiol. 64: 1968-1978, 1988). Simultaneous recordings from the intramuscular and esophageal electrodes were obtained during wakefulness and sleep. Changes in esophageal electrode activity were compared with changes in intramuscular electrode activity under four conditions: 1) voluntary maneuvers, 2) differences in state, 3) nasal airway occlusion during non-rapid-eye-movement sleep, and 4) spontaneous variations in respiratory efforts during non-rapid-eye-movement or rapid-eye-movement sleep. Although similar results were obtained from the esophageal and intramuscular electrodes, differences were present between the two recordings during both wakefulness and sleep. The esophageal electrode recorded activity from surrounding muscles during voluntary maneuvers, vocalization, and quiet breathing in wakefulness. Discrepancies between the two electrode recordings during sleep occurred under conditions of increased and decreased respiratory motor output. The data suggest that the esophageal electrode may not give an accurate assessment of PCA activity during many conditions in wakefulness and sleep.