ACOUSTICALLY INDUCED CORTICAL AROUSAL INCREASES PHASIC PHARYNGEAL MUSCLE AND DIAPHRAGMATIC EMG IN NREM SLEEP

Six healthy subjects (3 males, 3 females) were studied to assess phasi c inspiratory responses of upper airway (UA) and diaphragm muscles to electrocortical arousal independent of other potential respiratory sti mulation. Transient electroencephalographic (EEG) arousal (abrupt EEG frequency shift greater than or equal to 3 s without awakening) was in duced during supine stage 2 non-rapid-eye-movement (NREM) sleep with b inaural tone bursts (0.5 s, 4 kHz, 25-95 dB). Electromyograms (EMG) of levator veli palatini (EMGlvp) and genioglossus (EMGgg) were obtained with intramuscular electrodes, and EMG of diaphragm (EMGdi) was obtai ned with esophageal electrodes. EMG signals were processed as moving t ime-averaged inspiratory activity over 100-ms windows. For each arousa l, each of five consecutive postarousal breaths (R1-R5) was scored for peak inspiratory phasic EMG and normalized as percent averaged EMG of the three prearousal breaths for all muscles. After arousal, EMGlvp w as increased for R1-R5 and EMGgg and EMGdi were increased for R1-R4. T he increase in EMGlvp was greater than those of EMGgg and EMGdi for al l response breaths. There was a significant increase in EMGlvp in all subjects, and EMGgg and EMGdi were significantly increased in three an d two subjects, respectively. These data indicate that isolated transi ent electrocortical arousal is generally associated with phasic inspir atory recruitment of UA and diaphragm muscles in normal humans during NREM sleep; velopharyngeal muscle recruitment appears to be more consi stent and of greater magnitude and duration than that of oropharyngeal muscle or diaphragm. We speculate that transient arousal from sleep m ay contribute to UA patency independent of chemical and mechanical res piratory stimuli.