Background: The therapeutic value of transcutaneous electrical stimulation of the genioglossus muscle in patients with obstructive sleep apnea (OSA) to reduce sleep-disordered breathing is unclear.
Methods: Contraction of the genioglossus muscles during transcutaneous stimulation was investigated using ultrasonography in 11 healthy subjects (seven men, mean [SD] age 30  years; BMI, 24.2 [3.5] kg/m(2)). Esophageal and gastric pressures were measured with balloon catheters, and transesophageal diaphragm electromyogram (EMGdi) was recorded during polysomnography in 11 patients with OSA (eight men, aged 51  years; BMI, 42.0 [9.7] kg/m(2)) while transcutaneous electrical stimulation of the genioglossus was applied in non-rapid eye movement sleep (stage N2).
Results: Ultrasonography measurements showed a significant increase in tongue diameter during stimulation (sagittal: 10.0% [2.8%]; coronal: 9.4 % [3.7%]). The measurements were reproducible and repeatable. In patients with OSA, snoring decreased during stimulation (P < .001) and oxygenation improved (P = .001); the respiratory disturbance index (RDI) fell from 28.1 (26.3) to 10.2 (10.2) events per hour during stimulation (P = .002), returning to 26.6 (26.0) events per hour after stimulation was stopped. Transdiaphragmatic pressure swing decreased from 24.1 (13.5) cm H(2)O to 19.7 (7.1) cm H(2)O (P = .022), increasing to 24.2 (10.8) cm H(2)O afterward, and EMGdi fell from 23.8% max (12.6% max) to 15.7% max (6.4% max) (P < .001), rising to 22.6% max (10.4% max) post stimulation.
Conclusions: Continuous transcutaneous electrical stimulation of the genioglossus contracts the genioglossus muscle and reduces ventilatory load and neural respiratory drive in patients with OSA.