Objective:Compare whether the use of tracheal catheters of models 6.0 and 6.5 causes less sore throat in women after thyroid surgery compared with the traditional use of model 7.0 tracheal catheters.Methods: Investigators enrolled 180 female patients with American Society of Anesthesiologists (ASA) physical status I and III, aged 18-65 years, and scheduled for elective undergoing thyroid surgery with general anesthesia. The participants were randomly assigned into three groups(n=60 each group):Group A: Tracheal catheter group with an inner diameter of 6.0mm, Group B: Tracheal catheter group with an inner diameter of 6.5mm, Group C: Tracheal catheter group with an inner diameter of 7.0mm.The incidence and severity of postoperative sore throat were recorded in three groups at 1 h, 6 h, 24 h and 48 h after operation.

Inclusion Criteria:

• Female;
• Thyroid surgery should be performed under general anesthesia (GA) at an appropriate time;
• ASA grade I-III;
• Aged 18-65 years;
• BMI less than 35Kg/m2
• In line with ethics, patients voluntarily accept this experiment and sign informed consent.

Exclusion Criteria:

• Reflux esophagitis, preoperative sore throat, chronic pharyngitis, preoperative hoarseness, use of anticoagulants or corticosteroids, high risk of reflux or aspiration, dysphagia, previous oral or pharyngeal surgical intervention, bleeding disorder, severe heart, lung, liver and kidney dysfunction
• Upper respiratory tract infection occurred within 2 weeks before surgery
• Unable to insert ET (no more than two intubations)
• Patients with hoarseness or sore throat before surgery
• Language communication, hearing impairment or brain dysfunction such as stroke, unable to communicate

Healthy female thyroid surgery patients, ages 18-65 years, did not have serious systemic disease