End-Tidal Oxygen for Intubation in the Emergency Department

Inclusion Criteria: 1. The patient is located in the ED resuscitation bay of the participating centre. 2. The planned procedure is orotracheal intubation using a laryngoscope and RSI technique with preoxygenation for patients who are spontaneously breathing. 3. The patient is deemed to be at a high risk of hypoxia during RSI as per the treating ED clinician, as defined by: * Any patient requiring any form of oxygen therapy before preoxygenation. * Any patient with respiratory pathology based on clinical or radiological findings. Including, but not limited to: * Pneumonia, pulmonary oedema, acute respiratory distress syndrome (ARDS), aspiration, pulmonary contusion from trauma, infective exacerbations of known lung disease (e.g. asthma, pulmonary fibrosis, emphysema) or pulmonary embolism (PE) * Any patient with high oxygen consumption. Including, but not limited to: * Sepsis, Diabetic ketoacidosis, alcohol or drug withdrawal, seizures, thyrotoxicosis * Any underlying patient condition that may predispose to hypoxemia. Including, but not limited to: * Obesity, pregnancy, underlying lung disease (e.g. asthma, pulmonary fibrosis, emphysema), severe injury- hypovolaemia/haemorrhage. * or any other patient that the treating clinician has a high concern for hypoxemia during RSI. Exclusion Criteria: 1. Patient is known to be less than 18 years old. 2. The patient has a supraglottic device in-situ e.g iGel or LMA. 3. The patient is known to be pregnant. 4. The patient is known to be a prisoner. 5. The patient was intubated in the prehospital environment. 6. Immediate need for tracheal intubation precludes preoxygenation i.e. the patient is in cardiac arrest.