This prospective observational study evaluates whether the preoperative ROX index can predict early postoperative hypoxemia in patients undergoing bariatric surgery. Preoperative ROX measurements, along with ARISCAT and STOP-Bang scores, will be assessed for their association with hypoxemia occurring within the first 12 postoperative hours.

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

The study population consists of adult patients scheduled for elective bariatric surgery, including laparoscopic sleeve gastrectomy and Roux-en-Y gastric bypass. All participants are obese (BMI ≥ 35 kg/m²) and evaluated preoperatively in the anesthesia clinic prior to surgery.