Apneic Oxygenation Via Nasal Cannulae: 15 L/Min vs High-Flow

This is a randomized clinical trial investigating the utility of apneic oxygenation via nasal cannulae in the post-induction setting for the purpose of prolonging the safe apneic time. Three groups will be compared, a control group at 0 L/min, a 15 L/min and a 60 L/min group. The primary outcome will be the difference in the partial pressure of oxygen in arterial blood (PaO2) between groups throughout the nine-minute apneic period.

Airway management can be a life saving therapy. One major complication that may occur during airway management is a lack of oxygen in the blood. If severe or prolonged, this lack of oxygen can result in permanent brain damage, damage to other vital organs or even death. Strategies already exist to help prevent a lack of oxygen in the blood (hypoxemia), however research involving new ways to oxygenate patients may help to minimize the chance of hypoxemia during airway management. Apneic oxygenation is a novel method of delivering oxygen to a patient despite a lack of active respiration (i.e. the patient is not breathing on their own and the investigators are not providing the patient an artificial breath). The simplest and least invasive method to provide apneic oxygenation is the application of oxygen through nasal cannulae during airway management. Several different techniques to provide apneic oxygenation via nasal cannulae have been previously described(1-3), however randomized trials comparing these methods do not exist. This study will examine the change over time of the amount of oxygen dissolved in the blood (PaO2) in each of the three treatment groups: a control group (no apneic oxygenation), a 15 L/min group and a 60 L/min group. This data will help to determine the extent of benefit apneic oxygenation provides in this setting.

Eligibility Criteria:
Inclusion Criteria:

* American Society of Anesthesiologists Physical Status Classification 1 to 3
* Body Mass Index 28 to 35
* Elective surgery under general anesthesia

Exclusion Criteria:

* Evidence of difficult airway management (from patient history or clinical examination)
* Features suggestive of difficult bag mask ventilation
* Significant uncontrolled gastroesophageal reflux disease
* Significant respiratory disease (including severe asthma or chronic obstructive pulmonary disease, oxygen dependency, pulmonary hypertension, identified by pulmonary function tests or inability to climb one flight of stairs)
* Significant cardiac disease (ischemic heart disease, severe valvular disease, severe arrhythmia, congestive heart failure, ejection fraction \< 50%, inability to climb one flight of stairs)
* Inability to lie flat (skeletal deformities, orthopnea)
* Hemoglobin \< 100 g/L
* Pregnancy
* Neuromuscular disorder
* Known or suspected cervical spine instability
* Patients undergoing neurosurgical procedures
* Any clinical or radiological evidence of increased intracranial pressure
* Any expected requirement for rapid sequence intubation
* Allergy to any of the agents used for induction of general anesthesia in the study
* Contraindication to insertion of radial artery cannula
* Uncorrected coagulopathy
* Significant nasal obstruction