Upper Airway Stimulation in OSA

Anatomical basis of obstructive sleep apnea (OSA) is the collapse of the pharynx during sleep. It is considered as a result of complex interactions of structural and neuromuscular factors. Depth of sleep and body position have modulating effects. Although different areas of obstruction were identified, studies show that the sleep-mediated obstruction frequently occurs in the base of tongue area. Continuous positive airway pressure (CPAP) is the standard treatment for obstructive sleep apnea syndrome (OSAS) since more than 30 years. In several studies, treatment compliance was approximately 70%. So CPAP intolerance requires alternative surgical and non-surgical treatments. Functional electrical stimulation of upper airway muscles was investigated in the early 1980s. Studies have shown that stimulation of certain muscle groups increases the upper airway lumen. The major role of the hypoglossal nerve in upper airway obstruction was detected. The XII. cranial nerve innervates the genioglossus muscle, which stabilizes the anterior oropharynx substantially. Whereas a complete stimulation of the nerve leads to co-activation of other muscles including constrictors, the selective stimulation of anterior nerve branches causes advancement of the genioglossus. For hypoglossal nerve stimulation (HNS), the Inspire system and the ImThera device are currently approved in Europe. After extensive studies in animals and clinical examination of the concept of hypoglossal nerve stimulation (HNS), the results of the multicenter, prospective STAR study (Stimulation Therapy for Apnea Reduction) with the Inspire system were recently published. This study revealed that HNS can prevent the pharyngeal collapse without waking up the patient from sleep. The HNS with this device resulted in a significant improvement of both objective and subjective parameters of the severity of OSA. Electrical stimulation of the hypoglossal nerve is a new treatment for patients with moderate to severe OSA, who do not tolerate standard treatment.