Methods:

Men and women with moderate-to-severe OSA were recruited from 22 academic and private centers if difficulty accepting or adhering to continuous positive airway pressure (CPAP) treatment. A total of 724 subjects underwent screening. Subjects were excluded for body mass index (BMI) >32 kg/m², neuromuscular disease, severe lung disease, moderate or greater pulmonary hypertension, severe valvular heart disease, New York Heart Association class III heart failure, recent myocardial infarction, severe arrhythmias, uncontrolled hypertension, or active psychiatric disease. Data were collected from November 2010 to March 2013. Patients underwent a surgical procedure to implant the upper-airway stimulation system. The stimulation electrode was placed on the right medial division hypoglossal nerve (Cranial nerve XII) to recruit tongue-protrusion function; the sensing lead was placed between intercostal muscles to detect ventilatory effort; the pulse generator was implanted in the right anterior chest. Participants were instructed on use of a stimulator controller to initiate and terminate therapy on a nightly basis. Follow-up visits at 2, 6, and 12 months included a sleep study. The primary outcome measures were the apnea–hypopnea index (AHI; apnea hypopnea events per hour) and oxygen desaturation index (ODI; the number of times per hour the blood oxygen level drops by ≥4 percentage points from baseline).