Severe OSA Study (SOS)

Inclusion Criteria: 1. Provision of signed and dated informed consent form 2. Stated willingness to comply with all study procedures and availability for the duration of the study 3. Male or female, of any race, aged 18-80 years (inclusive) 4. Diagnosed with uncomplicated severe OSA (i.e., AHI \> 30 h-1); where uncomplicated is defined by the absence of: 1. Conditions that place the patient at increased risk of non-obstructive sleep-disordered breathing (e.g., central sleep apnea, hypoventilation, and sleep-related hypoxemia). Examples of such conditions include significant cardiopulmonary disease, potential respiratory muscles weakness due to neuromuscular conditions, history of stroke, and chronic opiate medication use. 2. Concern for significant non-respiratory sleep disorder(s) that require evaluation (e.g., disorders of central hypersomnolence, parasomnias, sleep-related movement disorders) or interfere with accuracy of HSAT (e.g., severe insomnia). 3. Environmental or personal factors that preclude the adequate acquisition and interpretation of data from HSAT. 5. Body mass index (BMI) \< 40 kg/m2 6. Neck circumference \< 50 cm 7. Absence of severe oxyhemoglobin desaturation during sleep, indicated by mean nocturnal SpO2 \> 87% 8. Mandibular range of motion \> 5 mm in protrusive direction 9. Adequate dentition, as determined by the site dentist Exclusion Criteria: 1. Inability to breathe through the nose comfortably 2. Presence of \> 25% CSA 3. Presence of positional obstructive sleep apnea per Cartwright's definition32 4. History of surgery intended to alter anatomy for the correction of OSA, such as uvulopalatopharyngoplasty (UPPP), maxillomandibular advancement (MMA), or tongue/hyoid suspension. History of surgery intended to restore normal anatomy, such as tonsillectomy, adenoidectomy, septoplasty, or polypectomy, is permitted 5. Presence of hypoglossal nerve stimulation device 6. Use of CPAP or OAT within the two weeks prior to the screening HSAT 7. History of OAT that has been demonstrated to provide effective therapy within the two years prior to the screening HSAT 8. Anticipated change in medical therapy during the study protocol that could alter OSA severity (e.g., weight loss surgeries; UPPP, MMA, tongue/hyoid suspension) 9. Loose teeth or advanced periodontal disease 10. History of temporomandibular joint disorder 11. Resistant hypertension, defined as inadequately controlled blood pressure despite therapy with ≥ 3 oral hypertensive agents 12. Presence of congestive heart failure, recurrent atrial fibrillation, or coronary artery disease 13. Presence of neuromuscular diseases, hypoventilation disorders, or cerebrovascular disease 14. Presence of pulmonary disease resulting in significant desaturation, e.g., severe chronic obstructive pulmonary disease, interstitial lung disease (SaO2 nadir of 87%), or pulmonary hypertension 15. History of cerebrovascular incident within the last 12 months 16. Use of pacemaker or other life supporting device 17. Anticipated change in body weight \> 5% during the study period 18. Participation in other studies that could interfere with the study protocol 19. Pregnancy or lactation 20. In the opinion of the investigator, unsuitable for inclusion in the study