Millions of patients undergo upper GI endoscopy in the United States each year. A large number of these patients have anesthesia to assist with their comfort during the procedure. The majority of patients do not have a protected airway during the procedure, meaning there is no endotracheal tube. Instead the current standard of care is to give supplementary oxygen via nasal cannula. Because patients are deeply sedated or have general anesthesia there is a risk for low oxygen saturation during the procedure, which presents a significant patient safety issue. The purpose of the clinical trial is compare the current anesthesia standard of care against high flow nasal cannula oxygen delivery during anesthesia. The investigator's hypothesis is that high flow nasal cannula oxygen delivery will decrease the frequency with which patients experience hypoxemia during anesthesia for upper GI endoscopy.

Inclusion Criteria:

1. Having Upper GI endoscopy expected to last greater than 15 minutes with anesthesia.
2. Age greater than or equal to 18 years

Exclusion Criteria:

1. Propofol, midazolam, or fentanyl allergy
2. Pre-procedure plan for general anesthesia with an endotracheal tube (at the discretion of the attending anesthesiologist)
3. Any procedure with planned electro-cautery as a high-inspired oxygen concentration could increase the risk for airway or esophageal fire.