CENTRAL AND REFLEX NEURAL CONTROL OF GENIOGLOSSUS IN SUBJECTS WHO UNDERWENT LARYNGECTOMY

Inspiratory activation of the genioglossus (GG) may occur by central d rive or as a reflex to negative airway pressure. To distinguish betwee n these, we studied seven laryngectomy patients who breathe via trache al stomas. Negative pressure stimuli (-15 and -25 cmH(2)O for 500 ms) were applied 1) at functional residual capacity and 2) during early in spiration via (i) the upper airway (UA) and (ii) the tracheal stoma. I ntraoral surface GG electromyogram was quantified, as described previo usly (R. L. Horner, J. A. Innes, K. Murphy, and A. Gut. J. Physiol. Le nd. 436: 15-29, 1991). Phasic GG activity was also measured from an in tegrated electromyogram during spontaneous and inspiratory loaded brea thing. Reflex GG activation occurred with negative UA pressure both at functional residual capacity and during inspiration (P < 0.001), but pressure stimuli at the stoma caused no significant activation (P = 0. 07). Phasic inspiratory activation occurred in four patients at rest a nd in all seven patients during inspiratory loading (P < 0.02). These patients demonstrate 1) reflex activation of the GG by negative UA pre ssure without airflow or respiratory effort and 2) central inspiratory GG activation that is not mediated by negative airway pressure.