This study aims to investigate the effectiveness and safety of implementing a personalized positive end-expiratory pressure (PEEP) management strategy guided by esophageal pressure (Pes), as well as its potential to reduce the occurrence of postoperative pulmonary complications (PPCs) in elderly patients undergoing laparoscopic surgery.

This trial is a single-blind, randomized, controlled, multicenter study. Elderly patients undergoing laparoscopic surgery under general anesthesia will be recruited according the inclusion and exclusion criteria. Participants in this study will be randomly assigned into two groups. The total sample size will be 232, with 116 participants in the experimental group and 116 participants in the control group. A stratified block randomization method will be employed, using the ARISCAT score for PPCs risk assessment and individual study centers as stratification factors. Anesthesia routine will be applied during pre-anesthetic preparation, anesthetic induction, maintenance and emergence except intraoperative respiratory management. In the control group, fixed PEEP of 3 cmH2O is applied throughout the procedure without lung recruitment maneuvers. While in the experimental group (Pes-Guided Group), continuous monitoring of end-expiratory esophageal pressure (Pes) is conducted. PEEP is chosen to maintain a positive transpulmonary pressure at end-expiration (PL = PEEP - Pes) after lung recruitment. PEEP titration following lung recruitment should be performed after endotracheal intubation or any procedure that may cause lung collapse, such as pneumoperitoneum, deflation or inflation of the endotracheal tube cuff, changes in position, or endotracheal suctioning. PEEP Titration is also required every hour after the establishment of pneumoperitoneum. Patients will be followed up within 7 days after surgery to assess basic vital signs, potential postoperative pulmonary complications (PPCs). Additionally, postoperative non-respiratory complications will be evaluated. Laboratory tests, the 15-item Quality of Recovery-15 (QoR-15) questionnaire, complications within 30 days after surgery, and 90-day survival rates will also be recorded.

Inclusion Criteria:

1. Patients aged 65 years or older, male or female
2. Scheduled to perform major laparoscopic surgery under general anesthesia
3. Expected duration of surgery ≥ 2 hours
4. Written informed consent is obtainable either from the patient or from a legal surrogate

Exclusion Criteria:

1. BMI ≥ 35 kg/m2.
2. History of pulmonary surgery (of any type).
3. History of severe chronic obstructive pulmonary disease (COPD) requiring non-invasive ventilation and/or home oxygen therapy.
4. Patients on systemic corticosteroid treatment for acute chronic obstructive pulmonary disease exacerbation.
5. Severe pulmonary arterial hypertension, defined as systolic pulmonary artery pressure > 40 mmHg.
6. Heart failure according to the New York Heart Association classification (class III or IV), ongoing hemodynamic instability, or severe shock (determined by the attending internist, cardiac index < 2.5 L/min/m2, or the requirement for positive inotropic drugs to maintain blood pressure).
7. Severe cardiac disease (acute coronary syndrome according to Canadian Cardiovascular Society, atrial flutter/fibrillation, sustained ventricular tachyarrhythmias, metabolic equivalent of tasks (METs) < 4) (METs < 4, determined by the inability to climb ≥ 2 flights of stairs).
8. Severe liver or renal dysfunction (Child-Pugh score 10-15, serum creatinine ≥ 2 mg/dL, or patients requiring peritoneal dialysis or hemodialysis).
9. Neuromuscular disease (of any type).
10. History of bone marrow transplantation or recent history of immunosuppressive drugs (chemotherapy or radiotherapy within 2 months before surgery).
11. Mechanical ventilation duration > 30 minutes within the past 30 days (e.g., surgery under general anesthesia).
12. Requirement for one-lung ventilation.
13. History of acute respiratory distress syndrome with potential need for prolonged postoperative mechanical ventilation.
14. Planned re-intubation after surgery.
15. Pregnancy (excluded by medical history and/or laboratory tests).
16. Brain injury or tumor.
17. Requirement for prone or lateral position during surgery.
18. Severe esophagogastric varices.
19. Enrollment in other interventional studies or refusal to sign informed consent.

De-identified individual participant data generated during the study will be made available on reasonable request to qualified researchers, following publication of the primary results, and in accordance with institutional and ethical guidelines.