The role of Oxygen Reserve Index (ORI) monitoring in optimizing apneic ventilation for laparoscopic cholecystectomy
Abstract
Background & objective: The Oxygen Reserve Index (ORI) is a non-invasive parameter utilizing multi-wavelength pulse co-oximetry. ORI can provide early warnings of deteriorating oxygenation before changes are reflected in SpO₂ levels. This study aimed to investigate the feasibility of non-ventilated intubation in patients undergoing cholecystectomy as a means to achieve safe intubation without nasogastric tube placement, with reduced trauma and cost, and improved time efficiency.
Methodology: After obtaining ethical committee approval and informed consent, 64 patients aged 18–60 years with ASA physical status I–II and Mallampati scores < 2 scheduled for cholecystectomy were enrolled. Standard monitoring was applied. Preoxygenation was performed using 100% oxygen with 8 breaths over 60 seconds, targeting an ORI value of 0.4. Patients were not ventilated by mask from induction to intubation. The ORI value at induction and at the 2nd minute (after allowing for muscle relaxation) were recorded. If the ORI dropped below 0.24 before the second minute, mask ventilation was initiated and the time was noted. Patients were evaluated for nasogastric tube requirement, surgeon satisfaction, and postoperative sore throat/laryngospasm. Correlations between ORI and BMI, age, and gender were analyzed.
Results: Based on the ORi™ threshold of 0.24, patients were divided into two groups: ORi™ < 0.24 and ORi™ ≥ 0.24. ROC analysis indicated threshold values of 80 kg for weight and 30 kg/m² for BMI. In the postoperative period, sore throat (30.8% vs. 2.6%) and laryngospasm (11.5% vs. 0%) were significantly higher in the ORi™ < 0.24 group. Regarding surgeon satisfaction, only 23.1% of surgeons were satisfied in the ORi™ < 0.24 group compared to 65.8% in the ORi™ ≥ 0.24 group, indicating significantly lower satisfaction in the former (P = 0.001).
Conclusion: We believe that apneic ventilation following induction may be safely applied in patients with BMI ≤ 30 when adequate preoxygenation is confirmed using ORI.
Abbreviations: FEV1: forced expiratory volume in one second, FVC: forced vital capacity, ORI: Oxygen Reserve Index
Keywords: Oxygen Reserve Index, apneic ventilation, body mass index
Citation: Çetinkaya S, Özcan ATD, Erdem AO, Özcan E, Özayar CCE, Güleç H. The role of Oxygen Reserve Index (ORI) monitoring in optimizing apneic ventilation for laparoscopic cholecystectomy. Anaesth. pain intensive care 2025;29(8):992-997. DOI: 10.35975/apic.v29i8.3037
Received: June 03, 2025; Revised: September 09, 2025; Accepted: September 21, 2025
