Local mechanisms drive genioglossus activation in obstructive sleep apnea

individuals with obstructive sleep apnea (OSA) require increased pharyngeal muscle dilator activation during wakefulness to maintain upper airway pate ncy. Negative pressure is one potential stimulus for this neuromuscular com pensation. Individuals with OSA who have previously undergone tracheostomy provide an opportunity to study upper airway physiology in both the presenc e and absence of upper airway respiratory stimuli. If negative pressure (or another local airway stimulus) were important in driving pharyngeal dilato r muscle activation, one would predict that during nasal breathing, the pha rynx of a tracheostomized patient would be exposed to negative pressure, an d that high levels of muscle activation would therefore be measured. Conver sely, during breathing by the patient through the tracheal stoma, one would expect tow levels of muscle activation in the absence of local stimuli. We measured a number of respiratory variables, including genioglossus activat ion under both nasal and tracheal stomal breathing conditions, in five pati ents. In all five patients there was a significant and substantial decrease in both peak phasic (100 +/- 0 to 53.4 +/- 9.2 arbitrary units [mean +/- S EM], p < 0.01) and tonic genioglossus activation (36.3 +/- 5.3 to 20.7 +/- 3.9 arbitrary units, p < 0.05) during stomal breathing as compared with nas al breathing. We conclude that local upper airway respiratory stimuli, poss ibly negative pressure, are important in mediating the increased pharyngeal dilator muscle activation seen in sleep apnea patients during wakefulness.