Electrical Stimulation of the Upper Airways Muscles

The upper airway muscles are importantly affected in obstructive sleep apnea syndrome (OSAS). The most important dilator, the genioglossus, shows augmented activity during wakefulness which decreases during sleep. Moreover, it shows greater fatigue and structural changes such as abnormal fiber morphology, inflammation and increased connective tissue in OSAS. Because of the crucial role of the muscles in the upper airway patency there is interest if electrical stimulation can improve the efficacy of the muscles and lead to new therapeutic options for OSAS. Indeed, the upper airways resistance can experimentally be reduced in animals, healthy persons and patients with OSAS using surface and intraneural stimulation. To translate these results in clinical application, apnea-triggered stimulation during sleep has been studied. However, although there were some positive effects the results were inconsistent and relevant side effects, such as arousals, were found.Tongue muscle training is the most recent approach to improve the function of the upper airways muscles.However, although snoring significantly improved there was no relevant reduction of respiratory disturbances in general. In conclusion, neurostimulation cannot be recommended for clinical use at this time. However, the available data prove the importance of the muscles in the pathophysiology of OSAS and the partial positive effects in patients encourage to go forward with this approach.