This is an observational, prospective study of patients undergoing a surgical procedure. Three parallel studies are taking place with collaborators in other countries. This study aims to bring novel insights regarding the benefits of pre-oxygenation combining standard oxygen facemask with high-flow nasal oxygen (HFNO), as opposed to standard oxygen facemask alone by assessing end-tidal oxygen (ETO2) levels after intubation.

This is an observational, prospective study of patients undergoing a surgical procedure. A total of 80 patients will be enrolled at BIDMC. Patients meeting inclusion criteria with no exclusions will be approached for consent. 40 patients receiving the pre-oxygenation face mask alone method during clinical routine and 40 patients using the pre-oxygenation combined facemask + HFNO technique as part of routine clinical care will be studied. No randomization will be employed. Choice of pre-oxygenation approach is at the discretion of the clinician. Patients will be enrolled as a convenience sample, such that the first 40 patients will be those with face mask alone, and the second 40 will be patients with face mask + HFNO. Research assistants will discuss the pre-oxygenation plan with the anesthesiologist as part of the screening process. Data will be collected including EtO2 levels during two minutes following intubation.

Methodology

1. Face mask alone: As per clinical standard, the standard oxygen facemask will be tightly applied on the face of the patient at 100% FiO2 for 3 to 4 minutes. In case of suspected full stomach, it is recommended to perform a rapid sequence induction and the patient does not receive bag-mask ventilation during the apnea period (45-60s). In the other case, a standard pre-oxygenation will be performed (see figure 1: experimental design of the study).
2. Face mask + Nasal cannula: As to clinical standards, the standard oxygen facemask will be tightly applied on the face of the patient at 100% FiO2 for 3 to 4 minutes and HFNO at 100% with a flow at 40 L/minutes during the pre-oxygenation (the flow can be decreased to less than 40 L/minutes if no tolerance by the patient). Then, after a general anesthesia induction and/or a rapid sequence induction is performed, the patient receives HFNO at 100% FiO2 and the flow of HFNO is increased to up to 80 L/minutes (which corresponds to a close delivered FiO2 at 80%) during the apnea period (1 to 2 min) until correct position of the endotracheal tube is confirmed with capnography.

Assessments The study does not require any research procedures other than passive data collection. For this study, EtO2 levels will be recorded at more frequent intervals than what is entered in the anesthesia record. Therefore, study staff will collect these data from the anesthesia machine in the operating room, where values are displayed on a breath-by-breath basis

Inclusion Criteria:

• 18 years and older
• All consecutive patients for scheduled or non-scheduled surgery with or without indication of rapid sequence induction (full-stomach)
• Undergoing general anesthesia with orotracheal intubation

Exclusion Criteria:

• Age < 18 years
• Hemodynamic instability
• Intubation without laryngoscopy (i.e., fiberoptic intubation for anticipated "cannot ventilate situation" or mouth opening < 2 cm), facial surgery
• Adults subject to legal protection
• Pregnancy (due to higher risk of oxygen desaturation and aspiration)

This study accepts patients undergoing a surgical procedure. Patients would be considered for eligibility regardless of race, ethnicity or gender.

This study will conduct anonymous data collection in order to ensure the anonymity of each person participating in the study. No information allowing the identification of persons will be communicated to third parties.