Effects of high-frequency oscillating pressures on upper airway muscles in humans

We examined the effects of high-frequency- (30-Hz) low-pressure oscillations (< 1 cmH2O) applied to the upper airway, via a nose mask, on genioglossus (EMGgg), sternomastoid (EMGsm), and diaphragm electromyogram (EMGdia) activity in sleeping humans. Ten patients with sleep apnea and six normal subjects were studied. The pressure oscillations were applied through the mask for a single breath. The subjects were studied in non-rapid-eye-movement (NREM) and rapid-eye-movement (REM) sleep. In the normal subjects, during NREM sleep, peak EMGgg, EMGsm, and EMGdia activity increased significantly in response to the oscillations in 63, 51, and 46%, respectively, of all trials. During REM sleep, significant increases occurred in 73, 88, and 13%, respectively, of all trials. Similar responses were observed in the patients with obstructive sleep apnea. Peak EMGgg, EMGsm, and EMGdia activity increased significantly in 74, 50, and 67%, respectively, of all NREM sleep trials and in 55, 81, and 76%, respectively, of all REM sleep trials. An important finding was that in 46% of the trials in the patients with sleep apnea the oscillation-induced increase in EMGgg activity was associated with a partial or complete reversal of the upper airway obstruction with an increase in tidal volume. This was observed in NREM and REM sleep. We conclude that there are upper airway receptors that respond to low-pressure-high-frequency oscillations applied to the upper airway that have input to the genioglossus and other muscles of respiration. These responses may be utilized in future treatment for sleep apnea.