Preoperative ROX Index and Postoperative Hypoxemia in Bariatric Surgery

Inclusion Criteria: * Adults aged 18-65 years * Scheduled for elective bariatric surgery (laparoscopic sleeve gastrectomy or Roux-en-Y gastric bypass) * Body mass index (BMI) ≥ 35 kg/m² * ASA physical status I-III * Able and willing to provide written informed consent Exclusion Criteria: * Acute respiratory failure, pneumonia, or active pulmonary infection * Receiving oxygen therapy or respiratory support (nasal cannula, CPAP, BiPAP, or high-flow oxygen) preoperatively * Preoperative SpO₂ \< 88% on room air * Significant cardiac arrhythmia, severe heart failure (NYHA class III-IV), or hemodynamic instability * Pregnancy, active malignancy, or current immunosuppressive therapy * Inability to complete postoperative follow-up or early discharge before 12-hour assessment