Perioperative pulmonary complications such as atelectasis, hypoxemia, and pneumonia after ventilatory management during general anesthesia have a negative impact on patient outcomes. The possibility of reducing perioperative pulmonary complications by lung recruitment, which uses positive pressure to prevent alveolar collapse, has been reported. Although laparoscopic surgery, which has been widely performed in recent years, can reduce the invasiveness of the operation, it is prone to alveolar collapse due to increased abdominal pressure and diaphragm elevation. The purpose of this study is to verify whether the lung recruitment during laparoscopic surgery in Trendelenburg head-down position prevents hypoxemia due to lung collapse.

The multi-center RCT will enroll 80 patients who have laparoscopic surgery in Trendelenburg head-down position. Informed consent will be obtained for study subjects who meet the selection criteria, and the subjects will be enrolled in Electronic Data Capture and randomized into two groups. Patients will be admitted to the operating room for induction of anesthesia and tracheal intubation. In the control group, mechanical ventilation will be performed according to the initial settings and protocols. In the intervention group, after intubation, the ventilator will be initially set up, and the first pulmonary recruitment will be performed immediately after the start of the laparoscopy, followed by recruitment every 30 minutes until the end of the laparoscopy.

Inclusion Criteria:

• Patients undergoing low head laparoscopic surgery who are expected to be laparoscopic for more than 2 hours

Exclusion Criteria:

• Lateral or supine position
• BMI > 35
• One-second rate <70%, %VC <80%, obstructive, restrictive, with bra
• Cardiovascular disease (NYHA III or higher)
• Intracranial hypertensive disease
• Emergency surgery
• Pregnancy
• Glaucoma
• Patients judged unsuitable by the anesthesiologist in charge