Submental stimulation and supraglottic resistance during mouth breathing.

We studied submental stimulation on supraglottic resistance (Rsg) in 5 normals and 6 patients with obstructive sleep apnea. We then examined the most effective sites of stimulation in the submental regions, and the relationships between Rsg and stimulation frequency and voltage in the supine position. Inspiratory and expiratory Rsg's were obtained as the slope of the linear portion of the pressure-flow relation determined at zero flow. Before stimulation, inspiratory and expiratory Rsg's were 0.76 ± 0.06 (means ± SE) and 0.61 ± 0.02 cmH2O · L−1 · sec, respectively, in normals, and 1.04 ± 0.20 and 0.92 ± 0.29 cmH2O · L−1 · sec, respectively, in patients. Stimulation in the proximal half submental region with surface electrodes 1 cm apart decreased inspiratory and expiratory Rsg's in patients, and inspiratory Rsg in normals. Inspiratory Rsg measured in this submental region showed a stimulation frequency-and voltage-dependency in both groups, but expiratory Rsg did not. These findings suggest that submental stimulation in the proximal half region widens the supraglottic airway during mouth breathing and probably involves the upper airway muscles.