• Hung-Wei Cheng, Chia-Yi Yeh, Man-Yun Chang, Chien-Kun Ting, and Po-Lun Chang.
• Department of Anesthesiology, Taipei Veterans General Hospital, Taipei, 112, Taiwan, ROC.
• J Clin Monit Comput. 2022 Oct 1; 36 (5): 1379-1385.

AbstractThe Oxygen Reserve Index (ORi™) is a dimensionless parameter with a value between 0 and 1. It is related to the real-time oxygenation status in the moderate hyperoxic range. The purpose of this study is to investigate the added warning time provided by different ORi alarm triggers and the continuous trends of ORi, SpO2, and PaO2. We enrolled 25 patients who were scheduled for elective surgery under general anesthesia with planned arterial catheterization before induction. The participants received standardized preoxygenation, induction, and intubation. The patients remained apneic and ventilation was resumed when the SpO2 fell below 90%. The ORi and SpO2 were recorded every ten seconds and arterial blood was sampled every minute, from preoxygenation to resumed ventilation. Alarm triggers set to the ORi peak and the ORi 0.55 values provided 300 and 145 s of significant added warning time compared to SpO2 (p < 0.0001). The coefficient of determination was 0.56 between the ORi and the PaO2 ≤ 240 mmHg and showed a positive correlation. The ORi enables the clinicians to monitor the patients' oxygen status during induction of general anesthesia and can improve the detection of impending desaturation. However, further studies are needed to assess its clinical potential in the high hyperoxic range.The protocol was retrospectively registered at ClinicalTrials.gov on July 21, 2021 (NCT04976504).© 2021. The Author(s), under exclusive licence to Springer Nature B.V.

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