Comparison of cerebral oxygen saturation values measured by different brands of near-infrared spectrometers under hypoxic conditions: a randomized controlled trial in healthy volunteers

By comparing the differences in cerebral oxygen parameters with 3 brands of near-infrared spectrometers, INVOS 5100C（Medtronic）, EGOS-600（Aegean）and BRS-1（Casibrain Technology）, to investigate their consistency, correlation and ability to detect key desaturation events in healthy volunteers in a hypoxic condition.

From December 6, 2021 to January 18, 2022, 20 healthy volunteers were recruited from our hospital. They were randomly divided into group E（a single sensor of INVOS 5100C at the left forehead and that of EGOS-600 at the right）and group B（INVOS 5100C and BRS-1, as the other group）, with 10 subjects in each group. After the sensors were applied to the forehead of the subject, hypoxia was induced and reversed by adjusting the ratio of inhaled nitrogen to oxygen. Regional cerebral oxygen saturation（rSO₂）, heart rate and pulse oxygen saturation（SPO₂）were continuously monitored and recorded in the whole process. Wilcoxon test was used to assess the baseline value and changes in rSO₂ between different devices. Bland-Altman and Deming regression analyses were employed to analyze the consistency and correlation between the 2 devices. Receiver operating characteristic（ROC）curve was plotted to analyze the performance of the different devices in detection of hypoxia.

All 3 devices responded similarly to the changes in inhaled oxygen concentration. ① The magnitude and rate of changes in rSO₂ for EGOS-600 and BRS-1 were less than those of INVOS 5100C. The ΔrSO₂ for INVOS 5100C, EGOS-600 and BRS-1 was 16%~34.15%, 6%~20.81% and 5%~23.81%, with an absolute median rate of change of（2.81~4.40）%/min,（1.50~2.14）%/min and（1.77~2.41）%/min, respectively. ②Bland-Altman analysis showed that the mean difference of EGOS-600 and BRS-1 to INVOS 5100C were 5.7 and 2.5 respectively. Deming regression displayed that the Person coefficient was 0.722 4 and 0.845 9, respectively（P<0.001）, which were in good consistency and correlation with INVOS 5100C. ③In terms of absolute values of 10%, 20% and 50% relative reduction in INVOS 5100C as the key interventional rSO₂ thresholds, EGOS-600 detection rates were 90%, 48% and 40% and BRS-1 detection rates were 80%, 48% and 50%. ④The ROC curve results indicated the AUC value was 0.893 and 0.715 for EGOS-600 and BRS-1, respectively, and the cut-off threshold for hypoxia prediction was 59.3% and 56.0%, respectively.

The response of EGOS-600 and BRS-1 to oxygenation changes is similar to that of INVOS 5100C, and the correlation and consistency are good, which can accurately predict brain oxygen changes.