THE EFFECTS OF TRANSCUTANEOUS ELECTRICAL-STIMULATION DURING WAKEFULNESS AND SLEEP IN PATIENTS WITH OBSTRUCTIVE SLEEP-APNEA

Upper airway (UA) collapse in obstructive sleep apnea (OSA) is considered in part to result from the decrease in UA dilator muscle tone that occurs during sleep. We hypothesized that augmentation of UA muscle function by transcutaneous electrical stimulation (TES) might function to enlarge UA size during wakefulness and/or prevent UA collapse during sleep in patients with OSA. Eight male patients with OSA were studied both awake and asleep, with TES administered to the submental region in two patients and to both the submental and subhyoid regions in six patients. Fast-CT scans obtained at FRC and end-inspiration (VTei) demonstrated increased UA size with tidal breathing, p less-than-or-equal-to 0.05. The active generation of -10 cm H2O pressure at FRC substantially decreased UA size, p less-than-or-equal-to 0.001. However, no changes in UA size were detected at either FRC or VTei with TES applied at 50 and 100% of the maximal tolerated intensity. The collapsibility of the UA in response to the generation of -10 cm H2O pressure was also unchanged by TES. In contrast to the lack of effect of TES on UA size, voluntary protrusion of the tongue increased cross-sectional area (CSA) of the orohypopharyngeal (OHP) segment of the UA, p < 0.05, and to a lesser extent the CSA of the distal velopharyngeal segment, p = 0.06. When applied during sleep, TES failed to prevent or improve either sleep-disordered breathing or sleep architecture. These results documented that TES applied in the submental and subhyoid regions was ineffective in enlarging the UA during wakefulness as well as in preventing UA collapse during sleep in patients with OSA. More direct and/or selective stimulation of UA muscles will likely be required if neuromuscular stimulation is to become an effective treatment tor OSA.