This prospective, randomized, double-blind study is intended to enroll a total of 100 patients with a BMI ≥ 40 kg/m2 and another 100 patients with a BMI ≥ 30 kg/m2 (but less than 40 kg/m2) undergoing surgery with general endotracheal anesthesia at Parkland Hospital. Patients will be randomized to receive either 15 L/min O2 or 15 L/min air from a standard nasal cannula during a simulated prolonged laryngoscopy. The anesthesia provider will do a direct laryngoscopy to ensure that the patient has a Cormack-Lehane grade I-II airway. Patients who have grade III-IV airways will be excluded from further study procedures and not analyzed. The rest of the anesthetic will not deviate from the standard of care. Anesthesia providers will be blinded as to whether patients are receiving oxygen or air during the apneic period.

Inclusion Criteria:

• 18-80 years old
• Obesity (BMI ≥ 30 kg/m2 ≤ 40 kg/m2)
• Morbid obesity (BMI ≥ 40 kg/m2)
• Scheduled for a non-emergent operation that requires general endotracheal anesthesia
• Willing and able to consent in English or Spanish
• No current history of advanced pulmonary or cardiovascular disease

Exclusion Criteria:

• Age less than 18 or older than 70
• BMI < 30 kg/m2
• Patient does not speak English or Spanish
• Family or personal history of malignant hyperthermia
• Patient refusal
• Monitored anesthesia care (MAC) or regional anesthesia planned
• Pregnant or nursing women
• "Stat" (emergent) cases
• Moderate to severe pulmonary disease (e.g., asthma, COPD, pulmonary fibrosis, pulmonary hypertension)
• Respiratory infection within the past 14 days (e.g., pneumonia, bronchitis)
• SpO2 < 97% on room air
• Moderate to severe cardiac disease (e.g., CHF, CAD, aortic stenosis)
• Severe gastroesophageal reflux disease (GERD)
• Nasal obstruction (e.g., tumor)
• Elevated intracranial pressure (e.g., brain tumor)
• History of difficult airway