A Randomized, Comparative, Controlled Study of Differences in the Incidence of Postoperative Sore Throat (POST) by Inner Diameter Size of the TaperGuardTM Endotracheal Tube (ETT)

1. Background and Rationale Postoperative sore throat (POST) is a frequent complication following general anesthesia with endotracheal intubation, significantly impacting patient satisfaction. The mechanism of POST involves localized trauma and subsequent inflammatory responses or mucosal edema caused by the endotracheal tube (ETT) and its cuff. The TaperGuard™ ETT, designed with a tapered polyvinyl chloride cuff, aims to reduce micro-aspiration compared to conventional cylindrical ETTs. Previous studies have demonstrated that the TaperGuard™ ETT results in a lower incidence of POST than cylindrical ETTs. Additionally, while research on cylindrical ETTs has shown that a smaller inner diameter (ID) correlates with a lower incidence of POST, this effect has not been specifically validated for the TaperGuard™ ETT. This study aims to evaluate whether using a one-size smaller TaperGuard™ ETT (ID 6.0 mm) further reduces POST compared to a standard size (ID 7.0 mm) in female patients.
2. Study Population and Randomization Female patients aged 19 to 70 with an ASA physical status of I-III scheduled for surgery under general anesthesia in the supine or lithotomy position will be enrolled. Participants will be randomly assigned to either the Control Group (Group C: ID 7.0 mm) or the Small Group (Group S: ID 6.0 mm) using a computer-generated random number sequence.
3. Anesthesia Protocol Induction: After 5 minutes of preoxygenation, anesthesia will be induced using intravenous lidocaine (40 mg), propofol (2 mg/kg), and rocuronium (0.8 mg/kg).

Intubation: Tracheal intubation will be performed using direct laryngoscopy. The ETT position will be confirmed via a fiberoptic bronchoscope to be 4 cm above the carina. The cuff will be inflated with air, and the pressure will be strictly adjusted to 22 cmH2O using a manometer.

Maintenance: Anesthesia will be maintained with sevoflurane (1.5-3.0%) and remifentanil (Target-Controlled Infusion, 2-3 ng/mL). Mechanical ventilation will be set to a tidal volume of 8 ml/kg and a respiratory rate of 10-12 cycles/min to target an EtCO2 of 30-35 mmHg. 4. Emergence and Recovery Five minutes before the end of surgery, fentanyl (50 mcg) will be administered intravenously. Upon completion of surgery, sevoflurane and remifentanil will be discontinued, and sugammadex (100 mg) will be administered for neuromuscular blockade reversal. Extubation will be performed when the patient's spontaneous tidal volume exceeds 200 ml and they follow verbal commands to open their eyes. 5. Outcome Assessment A blinded co-investigator, who is not involved in the anesthesia administration, will assess the presence and severity of POST and hoarseness. Assessments will be conducted at four time points: immediately upon arrival at the Post-Anesthesia Care Unit (PACU), and at 1, 6, and 24 hours postoperatively. The severity of POST will be recorded using an 11-point Numerical Rating Scale (NRS).