Similarly during intubation, the patient should be placed in the supine position with the neutral head. The endoscopic body of video rigid laryngoscope covered by a lubricated endotracheal tube enters the airway through the nasal cavity, then proceeds under visual conditions. When the epiglottis is exposed, if necessary, gently lift the patient's lower jaw so that the glottis is fully visible. The tube is pushed to approach and pass the glottis. Withdraw the endoscopic body while adjusting the depth of tube in the trachea. The intubation ends with tube fixation.

First of all, participants will be asked to take supine position with neutral head. The operator will insert a lubricated endotracheal tube through the nasal cavity into the oropharynx, while he/she holds the handle of video laryngoscope in his/her left hand. Laryngoscope blade can be placed into oral cavity along the right corner of the patient's mouth, and the tongue is pushed to the left by moving the handle. Blade should arrive at a suitable depth to fully expose the epiglottis and glottis. After that, the operator can push the catheter with the right hand to approach and pass the glottis, sometimes Magill forceps are necessary. Finally, the tube is inserted into the trachea to the appropriate depth and fixed firmly.

It is suggested to apply paraffin oil to the surface of the insertion tube of video fiberoptic scope, where the friction with the inner wall of the endotracheal catheter will be reduced. The insertion tube together with a lubricated endotracheal tube will be placed into the nasopharynx through the nasal cavity of patient who takes supine position with neutral head. Push the insertion tube slowly and continuously along the airway until cuff passes through the glottis. Next carefully, the endotracheal tube can be delivered into the trachea, and the insertion tube can be withdrawn from the trachea. At last, the tracheal catheter can be fixed after the depth is adjusted to an appropriate level.

According to the kinds of video methods uesd to assist in nasotracheal intubation, participants will be divided into video laryngoscope group. The data of the duration of catheter reaching oropharynx (T1), the duration of catheter reaching glottis (T2), successful intubation time (T3), the first-attempt intubation success rate, the total number of intubations for each participant, whether there is oral and nasal mucosa bleeding, whether the tracheal ring is pressed, whether the catheter is rotated, the heraodynamic changes, and the occurrence of throat complications within 2 hours after surgery, will be recorded respectively.

time requirements for delivering the anterior segment of the endotracheal tube from the nasal cavity to the oropharynx

time requirements for the anterior segment of the endotracheal tube from being put into the nasal cavity to the glottis being exposed

time requirements for delivering the anterior segment of the endotracheal tube from the nasal cavity to the trachea

number of successful first-attempt intubation/total number of intubations

average number of nasotracheal intubations for each participant

during nasotracheal intubation, whether airway soft tissue is damaged, such as bleeding