Am. J. Respir. Crit. Care Med., Volume 165, Number 1, January 2002, 71-77

Pharyngeal Pressure and Flow Effects on Genioglossus Activation in Normal Subjects

ATUL MALHOTRA, GIORA PILLAR, ROBERT B. FOGEL, JILL K. EDWARDS, NAJIB AYAS, TOSHIKI AKAHOSHI, DEAN HESS, and DAVID P. WHITE

Sleep Medicine Division and Pulmonary and Critical Care Division, Department of Medicine, Brigham and Women's Hospital and Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnea syndrome. Substantial data support the role of local mechanisms in mediating pharyngeal dilator muscle activation in normal humans during wakefulness. Using a recently reported iron lung ventilation model, we sought to determine the stimuli modulating genioglossus activity, dissociating the influences of pharyngeal negative pressure, from inspiratory airflow, resistance, and CO₂. To achieve this aim, we used two gas densities at several levels of end-tidal CO₂ and a number of intrapharyngeal negative pressures. The correlations between genioglossus electromyography (GGEMG) and epiglottic pressure across a breath remained robust under all conditions (R values range from 0.71 ± 0.07 to 0.83 ± 0.05). In addition, there was no significant change in the slope of this relationship despite variable gas density or CO₂ levels. Although flow also showed strong correlations with genioglossus activity, there was a significant change in the slope of the GGEMG/flow relationship with altered gas density. For the group averages across conditions (between breath analysis), the correlation with GGEMG was robust for negative pressure (R² = 0.98) and less strong for other variables such as flow and resistance. These data suggest that independent of central pattern generator activity, intrapharyngeal negative pressure itself modulates genioglossus activity both within breaths and between breaths.

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