When using a breathing circuit with heated wire humidifier, investigators will check if the temperature measured by the thermometer of the endotracheal tube is more than 0.25 degrees apart from the temperature measured by the esophageal thermometer. Through this, in the case of patients who need to use a breathing circuit with heated wire humidifier, investigators will find out whether it is appropriate to use an esophageal or endotracheal thermometer.

It is known that hypothermia occurs in approximately 50-90% of surgical patients under general anesthesia, and intraoperative hypothermia can lead to various complications such as wound infection, coagulation disorders, increased frequency of cardiac complications, ventricular fibrillation, prolonged effects of anesthesia drugs, shivering, and weakened immune function. Additionally, inadequate maintenance of temperature during surgery can result in delayed discharge from the recovery room, delayed recovery, and extended hospitalization. Therefore, accurate measurement of body temperature and active temperature management are crucial during surgery. Although there are various sites for temperature measurement, measuring the core body temperature in well-perfused deep tissues, which have a higher temperature and greater reliability than other sites, is essential. While esophageal temperature measurement is commonly used in patients undergoing general anesthesia, there may be cases where esophageal temperature probe cannot be inserted due to bleeding tendencies or lesions in the esophagus. In such cases, measuring temperature through the tympanic membrane or an endotracheal device becomes possible, but using a heated humidification breathing circuit for patient warming may affect the endotracheal temperature. Although there are animal study results comparing esophageal temperature and endotracheal temperature, research on the comparison of esophageal and endotracheal temperatures in humans is limited, and there is no study on the comparison of esophageal and endotracheal temperatures when using a heated humidification breathing circuit. The investigators aim to verify whether there is a temperature difference of 0.25 degrees or more between the temperature measured through the endotracheal device and the temperature measured by the esophageal thermometer when using a heated humidification breathing circuit. Through this investigation, they seek to determine which thermometer, either esophageal or endotracheal, is more appropriate to use in patients requiring the use of a heated humidification breathing circuit.

Inclusion Criteria:

• males and females between the ages of 20 and 60 and meet the criteria for classification I and II of the American Society of Anesthesiology

Exclusion Criteria:

• Patients with a predisposition for bleeding
• Patients with a history of inability to insert an esophageal thermometer (esophageal varices, esophageal stenosis, esophageal malformation, and anatomical deformation after esophageal surgery)
• pregnant woman

Among the patients undergoing surgery that requires more than 2 hours of general anesthesia and the use of a breathing circuit with heated wire humidifier