Table 1

Schedule for enrolment, interventions and assessments

Time point	Study period
	Enrolment	Intervention
	Preoperative visit*	Before anaesthesia	During anaesthesia	After anaesthesia	Completion visit†
Enrolment:
Eligibility	X
Informed consent	X
Demographic characteristics	X
Allocation		X
Interventions:
Sniffing position and McGrath Mac videolaryngoscope			X
Sniffing position and McGrath Mac videolaryngoscope with a masked screen			X
HELP and McGrath Mac videolaryngoscope			X
HELP and McGrath Mac videolaryngoscope with a masked screen			X
Assessments:
Proportion of orotracheal intubations for which the assistance of a nurse anaesthetist is required by the operator (primary outcome)			X
Intubation time			X
First intubation success rate
Visualisation of the glottis			X
Adjunctive manoeuvres and alternative techniques			X
Oesophageal intubation, failure and complications of tracheal intubation			X
Arterial oxygen desaturation			X
Difficulty with intubation (numerical scale and Intubation Difficulty Scale)			X
Kraus-adapted scale of cooperation			X
Evolution of vital signs			X
Hoarseness					X
Sore throat					X
Adverse events			X		X

*Preoperative visits are performed within the 2 weeks before the day of anaesthesia.
†Completion visits are usually performed on the first postoperative day but no later than 3 days after surgery (if surgery was performed on a Friday).
HELP,head-elevated laryngoscopy position.