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Upper Airway Stimulation in OSA Patients Resolves Multilevel Airway Collapse in a Dose-Response Manner

Objectives: Upper airway stimulation (UAS) is a potential therapy for continuous positive airway pressure (CPAP)–refractory obstructive sleep apnea by hypoglossal stimulation using an implantable, programmable neurostimulator. We tested the hypothesis whether changes in stimulation amplitude would modulate palatal and tongue-base airway size during wakefulness and sedation. Methods: Fifteen patients underwent digital video laryngoscopy while awake and/or drug-induced sleep (DISE) at least 3 months after UAS system implantation for CPAP-refractory obstructive sleep apnea (Inspire Medical Systems, Minneapolis, MN). Neurostimulation was applied at four increasing amplitudes: first sensation, tongue movement, titrated therapeutic, and sub-discomfort. Palatal and tongue-base cross-sectional area were measured and compared between periods with and without stimulation. Results: Twelve patients (all male, age: 51.2±9.0 years; AHI: 28.8±7.8/h) underwent DISE; fifteen patients (all male, age: 50.4±10.2 years; AHI: 29.3±7.5/h) underwent awake laryngoscopy and eleven patients and both. During both awake and DISE, higher stimulation amplitudes had a graded response in enlarging multi-level airway dimensions, with a larger percent increase of airway size during DISE. While awake, palatal area increased between 5.0±24.0% at the lowest stimulation to 73.0±79.3% at the titrated amplitude (P = 0.01), and tongue-base increased between 64.2±70.3% to 128.6±103.8% (P = 0.05). During DISE, palatal area increased from 9.3±30.4% to 215.4±305.2% (P = 0.09) and tongue-base from 12.0±45.4% to 177.3±166.4% (P = 0.01). Conclusions: Upper airway stimulation increases airway size during awake surgery and improves airway collapse during sedation. Increasing stimulation amplitudes enlarges both retro-palatal and retroglossal airway size. Increased multi-level airway size is a potential therapy mechanism of upper airway stimulation when treating CPAP-refractory OSA.