The study aims to compare the efficacy of Nasal High Flow Therapy (NHF) with low-flow oxygen supplementation in improving postoperative intermittent desaturations. If so, this mode of therapy would provide a cost effective, relatively easy to implement, and better tolerated treatment to Continuous Positive Airway Pressure (CPAP) for oxygen stabilization.

Patients identified preoperatively with previously diagnosed obstructive sleep apnea (intermittent collapse of upper airway while asleep) who refuse Continuous Positive Airway Pressure use after surgery and are treated with routine postoperative supplemental oxygen alone (1 liters per minute) will have more oscillation of oxygen saturation during the night (measure by overnight oximetry) than those treated with high nasal flow air insufflator (Fisher & Paykel Airvo 2 device) with same amount of oxygen supplement (1 liters per minute).

Inclusion Criteria:

1. Known diagnosis of obstructive sleep apnea by polysomnography (Apnea Hypopnea Index ≥ 5 events per hour) with recommendation of Continuous Positive Airway Pressure use.
2. The patient declines use of Continuous Positive Airway Pressure for the upcoming elective surgery.
3. The patient will require more than 48 hours of hospitalization.
4. Informed consent obtained from patient or approved designate.

Exclusion Criteria:

1. Predetermined need for Continuous Positive Airway Pressure post-operatively by surgical team.
2. Body Mass Index ≥ 40.
3. Patient with congestive heart failure and diagnosis of Cheyne- Stokes respiration or central apnea.
4. Patients who are oxygen dependent due to moderate to severe Chronic Obstructive Pulmonary Disease (Available Forced Expiratory Volume at 1 second of < 50% predicted) or advanced interstitial lung disease.
5. Preexisting chronic hypercapnia with known neuromuscular disease with respiratory involvement (e.g. Amyotrophic Lateral Sclerosis, myopathy).
6. Severe anemia necessitating blood transfusion.
7. Presence of tracheostomy.
8. Naso-oral malformation or severe nasal septal defect.
9. Presence of dementia or other diagnosed neurodegenerative disease.
10. Non-English speakers
11. Inability to provide informed consent.