INFLUENCE OF SLEEP ON GENIOGLOSSUS MUSCLE ACTIVATION BY NEGATIVE-PRESSURE IN NORMAL MEN

An important mechanism controlling genioglossus (GG) muscle activity i s the reflex response to negative airway pressure. We hypothesize that this reflex response may be lost during sleep and believe that this l oss may be important in the pathogenesis of airway collapse during sle ep. Thus, we determined the effect of non-rapid eye movement (NREM) sl eep on the GG electromyogram (EMG) response to brief (0.2 to 0.6 s) ep isodes of negative pressure generation (NPG) in the upper airway of si x normal subjects. Up to 100 NPGs (mean 58 +/- 12) were recorded both awake and during stable NREM sleep. During wakefulness, the change in GG moving time average EMG from basal to peak levels (during NPG) was 17.1 +/- 2.5 au (a 154 +/- 22% increase above basal levels). This resp onse was markedly reduced during NREM sleep (2.7 +/- 1.2 au; p < 0.01) . The latency of the GG EMG response was 53.8 +/- 11.5 ms during wakef ulness (n = 6), but much longer during sleep (132.7 +/- 24.5 ms; n = 3 ; p < 0.03). We conclude that in normal subjects (1) the GG muscle res ponds to negative airway pressure by reflex activation during wakefuln ess, and (2) this reflex activation is reduced or lost during NREM sle ep. We speculate that loss of this mechanism during sleep may contribu te to pharyngeal collapse in obstructive apnea patients.