Laparoscopic colorectal surgery is associated with an increased risk of intraoperative atelectasis due to pneumoperitoneum, Trendelenburg positioning, and prolonged anesthesia duration. Atelectasis developing during surgery may persist into the postoperative period and contribute to postoperative pulmonary complications. Automated lung recruitment maneuvers delivered by modern anesthesia ventilators may offer a standardized method to improve lung aeration and reduce atelectasis. This prospective, randomized, single-center controlled trial aims to evaluate the effect of automated intraoperative lung recruitment maneuvers on atelectasis detected by lung ultrasonography in patients undergoing elective major laparoscopic colorectal cancer surgery. Adult patients will be randomized to receive either automated lung recruitment maneuvers or standard mechanical ventilation without recruitment. Lung ultrasonography will be used to assess atelectasis at predefined perioperative time points. The primary outcome is the incidence of atelectasis detected by lung ultrasound, and secondary outcomes include postoperative pulmonary complications, length of intensive care unit stay, length of hospital stay, and perioperative hemodynamic instability.

This study is a prospective, randomized, single-center controlled clinical trial designed to evaluate the effects of automated intraoperative lung recruitment maneuvers on perioperative atelectasis and postoperative pulmonary complications in patients undergoing major laparoscopic colorectal cancer surgery under general anesthesia.

Despite its minimally invasive nature, laparoscopic colorectal surgery is associated with significant perioperative respiratory challenges. Pneumoperitoneum, Trendelenburg positioning, and prolonged operative duration may reduce functional residual capacity, impair respiratory mechanics, and promote intraoperative atelectasis. Atelectasis developing during general anesthesia can persist into the postoperative period and is a major contributor to postoperative pulmonary complications.

Although lung recruitment maneuvers are frequently used to improve lung aeration, manual application lacks standardization and reproducibility. Automated lung recruitment maneuvers delivered by modern anesthesia ventilators may provide a standardized and controlled approach to lung recruitment. Lung ultrasonography is a reliable, bedside, radiation-free imaging modality that allows real-time assessment of lung aeration and detection of atelectasis without the need for patient transport.

After confirmation of eligibility and arrival in the operating room, participants will be randomized in a 1:1 ratio to either an automated lung recruitment maneuver group or a control group receiving standard mechanical ventilation without lung recruitment. Standard intraoperative monitoring will be applied to all patients.

Lung ultrasonography will be used to assess lung aeration and detect atelectasis at predefined perioperative time points, including preoperative baseline assessment, intraoperative evaluation, and postoperative follow-up. Lung ultrasound scores will be used to quantify the degree of aeration loss.

In the intervention group, automated lung recruitment maneuvers will be performed intraoperatively using the anesthesia ventilator according to a standardized protocol. An individualized optimal positive end-expiratory pressure will be determined based on dynamic lung compliance and maintained throughout the surgical procedure. A repeat recruitment maneuver will be applied at the end of surgery after cessation of pneumoperitoneum. The control group will receive standard mechanical ventilation according to institutional practice. Perioperative fluid management will be standardized in both groups using a goal-directed fluid therapy approach.

Postoperative follow-up will include systematic assessment for pulmonary complications. Surgical complications, length of intensive care unit stay, and total hospital length of stay will also be recorded.

The primary outcome of the study is the incidence of atelectasis detected by lung ultrasonography. Secondary outcomes include postoperative pulmonary complications, perioperative hemodynamic instability, length of intensive care unit stay, and length of hospital stay.

This study aims to determine whether automated intraoperative lung recruitment maneuvers assessed using lung ultrasonography can reduce perioperative atelectasis and improve postoperative pulmonary outcomes in patients undergoing major laparoscopic colorectal surgery.

Inclusion Criteria:

• Age between 18 and 80 years
• Scheduled for elective laparoscopic colorectal cancer surgery
• American Society of Anesthesiologists (ASA) physical status I-III

Exclusion Criteria:

• ASA physical status IV or higher
• Pregnancy
• Body mass index (BMI) > 40 kg/m²
• Severe chronic obstructive pulmonary disease (COPD), GOLD stage III-IV
• Advanced heart failure with left ventricular ejection fraction <35%
• Previous thoracic surgery
• Preoperative requirement for supplemental oxygen therapy
• Refusal or inability to provide informed consent
• Intraoperative conversion to open surgery
• Development of significant hemodynamic instability during lung recruitment maneuvers

No IPD will be shared due to privacy regulations and lack of ethics approval for external data sharing