The sniffing position group used the conventional method of endotracheal intubation, the operation method was the same as that of the elevation position group, after the anterior part of the tracheal tube was inserted into the glottis, the head was still kept in the backward position, and the tube core was pulled out by another anesthesiologist (the core extubation force was less than 10N), and the endotracheal tube was inserted at the same time.

The operation methods of the research group are: left hand laryngoscope, inserted into the laryngeal cavity, fully exposed glottis, right hand tracheal tube from the right corner of the mouth into the mouth, direct vision to insert the anterior part of the endotracheal tube into the glottis, and then the assistant pulls out the tube core (the strength of the extubation core is less than 10N), so that the patient's jaw is adducted, the head remains in the "elevation" position, and the endotracheal tube is inserted at the same time

Intubation was performed with the head in the " elevation " position

Postoperative sore throat is defined as: persistent sore throat with the following grades: 1 point: no sore throat; 2 points: mild, accompanied by odynophagia; 3 points: moderate pain, persistent, worsening with swallowing; 4 points: severe, pain interferes with eating, requires the use of pain medication

Hoarseness is defined as a sound quality different from the preoperative voice and is graded as follows: 1 point: none, no hoarseness; 2 points: slight hoarseness, noticed by the patient; 3 points: moderate hoarseness, pronounced to observer; 4 points: severe hoarseness, loss of voice.