FUNCTIONAL ELECTRICAL-STIMULATION AND RESPIRATION DURING SLEEP

During obstructive sleep apnea (OSA), respiratory activation of upper airway muscles, particularly genioglossus, is ineffective during sleep . Functional electrical stimulation (FES) of muscles reportedly reduce s the number and length of OSAs. Our goals were to examine the effect of FES on sensation during wakefulness and on OSA events. Studies were performed in 11 subjects: 4 healthy asymptomatic subjects and 7 patie nts with OSA. Surface electrodes placed on the submental region produc ed discomfort; however, during sleep, the stimulus intensity producing arousal was significantly greater than that producing barely tolerabl e discomfort during wakefulness. Additionally, we developed a protocol for placement of fine-wire electrodes into the neurovascular bundle o f the hypoglossal nerve, using recognizable radiographic features and computerized axial tomography as guides. In these patients, while awak e, optimal wire placement was associated with visible tongue protrusio n without discomfort. With both surface stimulation and fine-wire FES, during sleep the stimulus intensity required to produce obvious elect roencephalographic arousal was significantly greater than that produci ng a barely tolerable sensation while awake. During apneic events, the application of surface stimulation had an inconsistent effect, termin ating 22% of the apneas, and fine-wire FES also had a limited impact, terminating 23% of the apneic events. We conclude from our studies tha t subjects tolerate surface and fine-wire FES to higher stimulus param eters during sleep than during wakefulness but that both approaches ha ve an inconsistent effect on apneas during sleep.