Can Atelectasis Be Prevented With Oxygen Reserve Index (ORI) Monitoring?

Can Atelectasis be Prevented in Robotic Surgery by Monitoring With Oxygen Reserve Index (ORI)? A Randomized Controlled Trial

This single-center randomized controlled trial aims to evaluate whether intraoperative monitoring using the Oxygen Reserve Index (ORI) reduces the incidence of postoperative atelectasis, as assessed by lung ultrasound (LUS), in adult patients undergoing elective robotic surgery under general anesthesia.

Postoperative atelectasis is observed in 60-90% of patients undergoing general anesthesia. Factors such as high inspired oxygen concentration, muscle relaxation, and reduced functional residual capacity contribute to its development through mechanisms like absorption atelectasis. The persistence of atelectasis increases the risk of pneumonia, hypoxia, prolonged hospital stay, healthcare costs, and mortality. Despite the well-known pathophysiology, the optimal intraoperative fraction of inspired oxygen (FiO₂) remains unclear.

The Oxygen Reserve Index (ORI) is a non-invasive, continuous parameter that reflects the oxygen reserve within the moderate hyperoxia range (100-200 mmHg). It may facilitate individualized FiO₂ titration to avoid hyperoxia-related atelectasis. Lung ultrasound (LUS) is a reliable, radiation-free bedside tool for detecting atelectasis.

This study hypothesizes that ORI-guided oxygen therapy will reduce the incidence of postoperative atelectasis compared to standard Peripheral Capillary Oxygen Saturation (SpO₂)-guided therapy.

Inclusion Criteria:

• American Society of Anesthesiologists Physical Status Classification System (ASA) physical status I-III
• Elective robotic surgery under general anesthesia
• Surgery duration >2 hours
• Requires invasive arterial cannulation
• Signed informed consent

Exclusion Criteria:

• ASA IV or higher
• Room air SpO₂ <92%
• Chronic pulmonary disease
• Hemoglobinopathy
• Pregnancy
• Refusal to participate