Effects of Positive End-Expiratory Pressure Levels on Lung Recruitment Duration and Hemodynamics After Alveolar Recruitment Maneuver: A Randomized Clinical Trial

Effects of Positive End-Expiratory Pressure Levels on Lung Recruitment Duration and Hemodynamics After Alveolar Recruitment Maneuver: A Randomized Clinical Trial

During general anesthesia surgery, the role of positive end-expiratory pressure (PEEP) in mechanical ventilation remains uncertain. Pressure levels above 0 cm H₂O can prevent postoperative pulmonary complications but may also cause intraoperative circulatory depression and lung injury due to overdistension. Using very low levels of PEEP may lead to atelectasis. However, high levels of PEEP can not only trigger complications such as intraoperative circulatory depression but also promote hyperinflation. Positive end-expiratory pressure (PEEP) is required to prevent atelectasis during lung-protective ventilation, and different levels of PEEP exhibit varying physiological and clinical effects when used alone or in combination with alveolar recruitment maneuvers (ARM). Alveolar recruitment maneuvers (ARM) are used to open atelectatic lung parenchyma, but the duration of their benefits has not been clearly determined. This study aims to determine the effectiveness of different PEEP levels after ARM in general anesthesia surgery, the duration of their time-dependent responses, and their hemodynamic effects, providing a reference for how often recruitment maneuvers should be performed during general anesthesia and further refining the specific details of lung-protective ventilation strategies.

Inclusion Criteria:

• ASA physical status classification: Ⅰ or Ⅱ or Ⅲ
• Adults aged 18 to 80 years, regardless of gender.
• Patients undergoing elective laparoscopic colorectal cancer surgery under general anesthesia.
• Patients who have provided written informed consent after understanding the study purpose, procedures, and potential risks.

Exclusion Criteria:

• Recent thoracic surgery; radiographic evidence of pneumothorax, emphysema, or pulmonary bullae;
• Pulmonary diseases: asthma or severe obstructive ventilatory dysfunction; preoperative pulse oxygen saturation (SpO2) < 90% on room air or < 95% with supplemental oxygen; contraindications to ARMs (e.g., intracranial hypertension, hypovolemic shock, or right heart failure);
• severe cardiac disease (NYHA class III/IV, acute coronary syndrome, sustained ventricular tachycardia); concurrent participation in another trial; or refusal to provide informed consent