CPAP vs AutoCPAP for Treatment of Obstructive Sleep Apnea (OSA) in the Postoperative Setting

Inclusion Criteria: 1. Known OSA patients well-controlled by CPAP (not hypoxemic i.e. Oxygen Saturation (SaO2) ≥ 89% and post-treatment Apnea Hypopnea (AHI) \<10) and compliant ( \> 3 hours per night) presenting for elective inpatient surgery to MetroHealth Medical Center 2. Elective extremity or lower abdominal surgery 3. Age \>18 years Exclusion Criteria: 1. Surgery that may cause hypoxemia from causes other than the effect on upper airway patency e.g. any thoracic surgery, upper abdominal surgery, head and neck surgery. 2. Surgery on the upper-airway. 3. Any condition that may interfere with application of CPAP mask e.g. trauma, surgery on the face, vomiting, naso-gastric intubation etc. 4. OSA treated with a device other than CPAP e.g. Bilevel positive pressure or V-Positive Airway Pressure 5. OSA needing very high levels of CPAP i.e. \> 16 cms to achieve adequate control 6. OSA or other underlying cardiopulmonary conditions that require supplemental oxygen 7. Patients with decompensated congestive heart failure or advanced Chronic Obstructive Pulmonary Disease (COPD) (FEV1\<35% of predicted) 8. Patients with neuromuscular impairment 9. Patients with central sleep apnea 10. Pregnant patients 11. Decisional impaired subjects who are not able to consent