Laparoscopic cholecystectomy and the associated pneumoperitoneum can impair diaphragmatic mechanics and reduce postoperative oxygenation. This prospective observational study aims to evaluate perioperative changes in diaphragmatic excursion measured by ultrasonography and to investigate their association with early postoperative oxygenation parameters and hypoxemia. By correlating diaphragmatic excursion changes with SpO₂/FiO₂ and the ROX index, the study seeks to clarify the physiological contribution of diaphragmatic dysfunction to postoperative hypoxemia in patients undergoing laparoscopic cholecystectomy.

Inclusion Criteria:

• Adults aged 18-75 years
• Scheduled for elective laparoscopic cholecystectomy under general anesthesia
• Able to undergo diaphragm ultrasonography (no preoperative barrier to assessment)
• Able to cooperate with preoperative and early postoperative diaphragm measurements
• Postoperative oxygenation data available (SpO₂, FiO₂, and SpO₂/FiO₂ can be recorded)
• Provided written informed consent

Exclusion Criteria:

• Morbid obesity (BMI ≥ 40 kg/m²)
• Known diaphragmatic paralysis, phrenic nerve injury, or hemidiaphragm dysfunction
• Severe COPD, restrictive lung disease, or advanced parenchymal lung disease
• Preoperative home oxygen therapy or CPAP/BiPAP/home mechanical ventilation
• Conversion to open surgery (laparoscopic → open)
• Hemodynamic instability preoperatively or intraoperatively; emergency/complicated surgery
• Factors preventing ultrasound assessment (e.g., marked upper abdominal gas, large scar/wound, severe subcutaneous edema)
• Same-day discharge cases with <24-hour observation
• Inability to complete measurements (e.g., severe cognitive impairment, poor cooperation, severe pain preventing measurement)
• Incomplete data not compatible with the protocol

The study population consists of adult patients aged 18-75 years undergoing elective laparoscopic cholecystectomy under general anesthesia at a tertiary care center. Eligible participants are patients without known diaphragmatic dysfunction or severe underlying pulmonary disease, in whom perioperative diaphragm ultrasonography and postoperative oxygenation measurements can be reliably performed. All participants provide written informed consent and receive standard perioperative care without any study-related intervention.