Upper airway anesthesia reduces phasic genioglossus activity during sleep apnea.

We hypothesize that stimulation of upper-airway mechanoreceptors during obstructive apnea augments upper airway muscle activity. If so, upper-airway anesthesia (UAA) should reduce mechanoreceptor output and therefore upper-airway muscle activity. To test this hypothesis, we studied the effect of UAA on the relationship between the phasic activity of the moving-time average (MTA) of the genioglossus electromyogram (EMG-GG) and the esophageal pressure deflection (DP) during obstructive apneas in non-rapid-eye-movement (NREM) sleep in a group of six men with severe sleep apnea. Before UAA, the phasic EMG-GG was linearly related to the deflections in esophageal pressure (DP) during the last three occluded breaths (both progressively increased). After UAA, the mean ratio of EMG-GG to DP decreased to 23% of the control value, from 0.17 +/- 0.04 to 0.04 +/- 0.01 (mean +/- SEM) arbitrary units/cm H2O (p < 0.05). The mean slope of the EMG-GG-versus-DP regression lines also decreased to 23% of the control value, from 0.22 +/- 0.03 to 0.05 +/- 0.01 arbitrary units/ cm H2O (p < 0.01). These findings suggest that stimulation of upper-airway mechanoreceptors during obstructive apnea in NREM sleep augments phasic genioglossus activity.