Before surgery, all participants received a radial arterial line. Participants were then placed supine, in a 10 degrees reverse Trendelenburg position. Preoxygenation was then performed using atight fitting face mask and having Tracheal intubation was thereafter performed using a video laryngoscopewhen the anaesthetist assessed the conditions as appropriate in the control group (Group C).The correct placement of the tracheal tube was confirmed visually by the anaesthetist in charge and a member of the study team. The tracheal tube was secured, and the participant was left apnoeic with the tracheal tube open to the atmosphere until the peripheral oxygen saturation declined to 93% or apnoea is sustained for 5 minutes.

The continuous laryngeal oxygen supply group (Group B) used the same preoxygenation and anesthesia induction methods as the control group. When intubation conditions were assessed to be met, laryngoscopy was performed to evaluate the airway. If the laryngoscopic view was Cormack and Lehane grade 3 or grade 4, the subject was excluded from the study and tracheal intubation was performed. Otherwise, continuous laryngeal oxygen supply was initiated through a modified disposable video laryngoscope blade, which has an internal lumen. The distal end of the blade is connected to an oxygen delivery tube, and the other end of the oxygen delivery tube is connected to a flowmeter, with an oxygen flow rate of 10 L/min to maintain a continuous oxygen supply to the larynx. During apnoea, anaesthesia was maintained with intermittent boluses of propofol and, if necessary, either infusion of remifentanil. Upon reaching an SpO2 of 93% or apnoea is sustained for 5 minutes, tracheal intubation and mechan

Before surgery, all participants received a radial arterial line. At arrival to the operating theatre, ECG, invasive arterial blood pressure, pulse oximetry, and train-of-four monitoring were applied. An i.v. line was secured, and a standard infusion of electrolyte solution was started. Participants were then placed supine, in a 10 degrees reverse Trendelenburg position. Preoxygenation was then perform using atight fitting face mask and having each subject breathe 100% O2 at 15 L/min.Tracheal intubation was thereafter performed using a video laryngoscope when the anaesthetist assessed the conditions as appropriate in the control group (Group C).The correct placement of the tracheal tube was confirmed visually by the anaesthetist in charge and a member of the study team. The tracheal tube was secured, and the participant was left apnoeic with the tracheal tube open to the atmosphere until the peripheral oxygen saturation declined to 93% or apnoea is sustained for 5 minutes.

arterial partial pressure of oxygen (PaO2) at 3 min when intubation criteria are met