Early postoperative hypoxemia is a frequent complication after elective ear, nose, and throat (ENT) surgery and may adversely affect recovery in the post-anesthesia care unit (PACU). Simple and non-invasive preoperative tools to identify patients at risk for early postoperative hypoxemia are limited.

The ROX index, calculated using oxygen saturation, fraction of inspired oxygen, and respiratory rate, is an easily applicable bedside parameter that has been shown to predict respiratory deterioration in various clinical settings. However, its predictive value in the preoperative period for patients undergoing elective ENT surgery has not been well established.

This prospective observational study aims to evaluate the association between the preoperative ROX index measured on room air and early postoperative hypoxemia in adult patients undergoing elective septorhinoplasty or endoscopic sinus surgery under general anesthesia. Early postoperative hypoxemia will be defined as oxygen saturation below 92% or the need for supplemental oxygen at a flow rate of 4 L/min or higher within the first 30 minutes after PACU admission. The predictive performance of the ROX index will be assessed using receiver operating characteristic (ROC) analysis.

Inclusion Criteria:

• Age between 18 and 65 years
• American Society of Anesthesiologists (ASA) physical status I-II
• Scheduled for elective septorhinoplasty or endoscopic sinus surgery
• Undergoing surgery under general anesthesia
• Ability to undergo preoperative measurement of oxygen saturation and respiratory rate on room air
• Provision of written informed consent

Exclusion Criteria:

• Age <18 years or >65 years
• ASA physical status III or higher
• Known severe cardiopulmonary disease (e.g., advanced chronic obstructive pulmonary disease, pulmonary hypertension, severe heart failure)
• Active respiratory tract infection in the preoperative period
• Body mass index (BMI) >35 kg/m²
• Requirement for long-term supplemental oxygen therapy
• Refusal or inability to provide informed consent

Adult patients aged 18 to 65 years with American Society of Anesthesiologists (ASA) physical status I-II who are scheduled for elective septorhinoplasty or endoscopic sinus surgery under general anesthesia will be included in this study. All participants will undergo standard preoperative assessment, including measurement of oxygen saturation and respiratory rate on room air, and will be monitored postoperatively in the post-anesthesia care unit (PACU) according to routine clinical practice.