The purpose of this multicenter, randomized controlled trial (ULTRASVENT-2) is to evaluate the effect of different positive end-expiratory pressure (PEEP) levels on postoperative oxygenation and lung aeration in adult patients undergoing elective non-cardiac and non-thoracic surgery under general anesthesia. Moving away from traditional binary outcomes, this study utilizes a continuous functional metric, the non-invasive oxygenation index SpO2/FiO2 (S/F ratio), as the primary endpoint to precisely capture the degree of respiratory function preservation.
Patients will be stratified into four distinct surgical cohorts based on the type and aggressiveness of the procedure: non-abdominal surgery, major open abdominal surgery, major laparoscopic abdominal surgery, and low-trauma laparoscopic surgery. This adaptive design aims to investigate how protective PEEP strategies interact with varying degrees of surgical trauma and intraoperative pneumoperitoneum, allowing the optimization of mechanical ventilation parameters for routine clinical practice.
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.
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.