Genioglossal inspiratory activation: central respiratory vs mechanoreceptive influences

Upper airway dilator muscles are phasically activated during respiration. We assessed the interaction between central respiratory drive and local (mechanoreceptive) influences upon genioglossal (GG) activity throughout inspiration. GG_EMG and airway mechanics were measured in 16 awake subjects during baseline spontaneous breathing, increased central respiratory drive (inspiratory resistive loading; IRL), and decreased respiratory drive (hypocapnic negative pressure ventilation), both prior to and following dense upper airway topical anesthesia. Negative epiglottic pressure (P_epi) was significantly correlated with GG_EMG across inspiration (i.e. within breaths). Both passive ventilation and IRL led to significant decreases in the sensitivity of the relationship between GG_EMG and P_epi (slope GG_EMG vs P_epi), but yielded no change in the relationship (correlation) between GG_EMG and P_epi. During negative pressure ventilation, pharyngeal resistance increased modestly, but significantly. Anesthesia in all conditions led to decrements in phasic GG_EMG, increases in pharyngeal resistance, and decrease in the relationship between P_epi and GG_EMG. We conclude that both central output to the GG and local reflex mediated activation are important in maintaining upper airway patency.