Genioglossal activation in patients with obstructive sleep apnea versus control subjects. Mechanisms of muscle control.

Pharyngeal dilator muscle activation (GGEMG) during wakefulness is greater in patients with obstructive sleep apnea (OSA) than in healthy control subjects, representing a neuromuscular compensatory mechanism for a more collapsible airway. As previous work from our laboratory has demonstrated a close relationship between GGEMG and epiglottic pressure, we examined the relationship between genioglossal activity and epiglottic pressure in patients with apnea and in control subjects across a wide range of epiglottic pressures during basal breathing, negative-pressure (iron-lung) ventilation, heliox breathing, and inspiratory resistive loading. GGEMG was greater in the patients with apnea under all conditions (p < 0.05 for all comparisons), including tonic, phasic, and peak phasic GGEMG. In addition, patients with apnea generated a greater peak epiglottic pressure on a breath-by-breath basis. Although the relationship between GGEMG and epiglottic negative pressure was tight across all conditions in both groups (all R values > = 0.69), there were no significant differences in the slope of this relationship between the two groups (all p values > 0.30) under any condition. Thus, the increased GGEMG seen in the patient with apnea during wakefulness appears to be a product of an increased tonic activation of the muscle, combined with increased negative-pressure generation during inspiration.