Clinical Research Directory

Inclusion Criteria: * Age greater than or equal to 18 years. * Planned elective non-cardiac and non-thoracic surgical intervention requiring general anesthesia with mechanical ventilation. * Airway protection utilizing an endotracheal tube. * Assignment to one of the four specific surgical strata: non-abdominal, major open abdominal, major laparoscopic abdominal, or low-trauma laparoscopic surgery. * Baseline lung ultrasound showing no pathological findings, corresponding to a total preoperative LUS score of 0. * Technical feasibility of performing a postoperative lung ultrasound within the first 2 hours after the completion of surgery. * Signed written informed consent to participate in the clinical trial. Exclusion Criteria: * Planned cardiac or thoracic surgery (e.g., coronary artery bypass grafting, valve replacement, heart transplantation, lung resection, esophageal surgery). * Pneumothorax diagnosed before or during the surgical procedure. * Inability to adequately visualize the target dorsal-basal lung zones by ultrasound due to physical limitations (e.g., morbid obesity, massive surgical dressings, anatomical anomalies, or dermatological lesions in the scanning area). * Presence of hydrothorax detected on the baseline preoperative ultrasound. * Confirmed perioperative aspiration of gastric contents or other foreign material. * Any pathological changes identified during the baseline ultrasound of the dorsal-basal lung regions (a total preoperative LUS score greater than 0). * Requirement for massive blood transfusion during the surgery, defined according to local institutional criteria. * Surgical interventions directly involving or violating the diaphragm. * Expected inability to conduct reliable postoperative clinical and ultrasound assessments (e.g., need for deep sedation preventing wakefulness and contact, or planned transfer to another facility).