Table 1 Clinical data collected (with no identifying data)

(a) Pre-oxygenation

• Time pre-oxygenation started

• Position adopted for pre-oxygenation

• Duration of pre-oxygenation (time of induction = end of pre-oxygenation)

• SpO₂ at beginning and end of pre-oxygenation (i.e. prior to induction)

• Mode of pre-oxygenation (HFNC, NRM)

• Lowest SpO₂ during pre-oxygenation

• Name, dosages, and timing of pre-medications given

(b) Intubation

• Time induction agent given, name of induction agent, and dose

• Time paralytic agent given, name of paralytic agent, and dose

• Time of successful intubation

• Lowest SpO₂ achieved during subsequent intubation attempts (if unsuccessful at first attempt)

• SpO₂ at the end of intubation

• Type of laryngoscope use (direct/articulating/video)

• Adjunct devices use (e.g. bougie)

• Position of intubation

• Cormack-Lehane scoring of laryngeal view (state direct or video view)

• Intubator speciality and level of experience (by post-graduate year)

• Supervision by EM specialist (yes/no)

• Peri-intubation adverse events: hypotension, hypertension, tachycardia, bradycardia, regurgitation, aspiration, cardiac arrhythmia, cardiac arrest during RSI, oropharynx or dental trauma

(c) Clinical outcomes

• Length of stay in ICU

• As in secondary endpoints

(d) Difficult airway features

• Reduced neck mobility or on cervical collar

• Mallampati score

• Mouth opening

• Thyromental distance

• Airway obstruction

• Facial trauma (if not severe enough to preclude recruitment as per exclusion criteria)

• Blood or vomitus in airway

(e) Others

• Demographics (age, gender, ethnicity, body mass index)

• Comorbid conditions (congestive cardiac failure, ischemic heart disease, atrial fibrillation, chronic renal disease, chronic obstructive pulmonary disease, asthma, obstructive sleep apnoea, diabetes, previous head and neck radiation, head and neck mass or infection, upper gastrointestinal bleeding)

• Pre-oxygenation vital signs (temperature, heart rate, systolic BP, diastolic BP, mean arterial pressure, Glasgow Coma Scale)

• Quick SOFA score at triage and prior to pre-oxygenation

• CXR findings

• Indication for intubation

• Vasopressor use