Validation Experiment of a New Brain Oxygen Saturation Monitoring Instrument
Authors: Chen Kai , liu Zunxu , Li Meng-Yun , Tang Lijuan , Zou Yufeng , Xiao Kailin , zhang zongze 
Published: October 2021

Abstract
Background The blood samples of jugular vein and radial artery were obtained from healthy adults by induced oxygen desaturation test under pulse oximetry conditions on each platform. The oxygen saturation of the two blood samples was analyzed and measured by a Co-oximeter. Thus, the oxygen saturation value of jugular vein (SjvO2) and radial artery (SaO2) were obtained. According to the clinical empirical formula Sa/vO2 = 0.7×S jvO2 + 0.3×SaO2, the oxygen saturation value of brain tissue for invasive blood gas analysis was calculated. To calculate the difference between brain oxygen saturation (rSO2) measured by brain oxygen saturation monitor (hereinafter referred to as brain oxygen analyzer) and brain oxygen saturation (Sa/vO2) measured by invasive blood gas analysis, analyze the consistency of brain oxygen saturation measured by brain oxygen saturation analyzer and blood gas analyzer, and calculate the accuracy of brain oxygen saturation monitoring. The blood samples of jugular vein and radial artery were obtained from healthy adults by induced oxygen desaturation test under pulse oximetry conditions on each platform. The oxygen saturation of the two blood samples was analyzed and measured by a Co-oximeter. Thus, the oxygen saturation value of jugular vein (SjvO2) and radial artery (SaO2) were obtained. According to the clinical empirical formula Sa/vO2 = 0.7×S jvO2 + 0.3×SaO2, the oxygen saturation value of brain tissue for invasive blood gas analysis was calculated. To calculate the difference between brain oxygen saturation (rSO2) measured by brain oxygen saturation monitor (hereinafter referred to as brain oxygen analyzer) and brain oxygen saturation (Sa/vO2) measured by invasive blood gas analysis, analyze the consistency of brain oxygen saturation measured by brain oxygen saturation analyzer and blood gas analyzer, and calculate the accuracy of brain oxygen saturation monitoring. MethodsIn healthy adult volunteers, the induced desaturation test, in which blood gas analysis measures the subjects' internal jugular vein and carotid artery blood samples at each pulse oximetry platform range. Clinical trials were conducted to verify the expected effectiveness and safety of the brain oxygen saturation monitor. Ten subjects were selected into the study according to strict inclusion criteria and exclusion criteria. Subjects should monitor their electrocardiogram, pulse, blood pressure, SPO2 and other vital signs, perform retrograde puncture catheterization of internal jugular vein and radial artery catheterization, ensure the safety of subjects during the period, and record the values of blood samples before and after collection. The oxygen was lowered according to the set platform(according to Figure2), and physiological parameters were monitored during the process. There were 9 platforms in total, and each platform lasted about 5 minutes. The oxygen saturation value of jugular vein (SJVO2) and the oxygen saturation value of carotid artery (SaO2) were obtained, and the tissue oxygen saturation value of sa1vO2 was calculated according to the clinical empirical formula SA1VO2 = 0.7xSJVO2 + 0.3xSaO2. During the blood collection process, the blood oxygen saturation (RSO2) of the subjects' brain was continuously monitored by tissue oximeter noninvastively. The consistency of non-invasive monitoring value RSO2 and invasive measurement value sa1vO2 was compared, and scientific statistical analysis was carried out to confirm whether the accuracy of tissue oxygen meter meets clinical requirements. ResultsAbsolute accuracy evaluation: Further linear regression analysis was performed on the non-invasive monitoring value of the test instrument and the blood gas analysis detection value. The fitting linear equation was rSO2=4.89+0.93×Sa/vO2, where the slope was 0.93, close to 1. The regression line was close to the 45° diagonal trend. The correlation coefficient between rSO2 and Sa/vO2 was 0.95, indicating that there was a good correlation between the non-invasive monitoring value and the invasive blood gas analysis value. Trend accuracy evaluation: It can be seen that the average difference between the trend change value of the test instrument monitoring value and the blood gas analysis value is very small (Bs=Means(△rSO2-△Sa/vO2)=-0.32%), indicating that the trend change of the test instrument monitoring value and the blood gas analysis value is basically consistent in statistical significance. The 95% consistency interval of the difference of trend change between the two devices is narrow ([BS-1.96SD, Bs+1.96SD]=[-6.13%, 5.5%]), indicating that the difference of trend change between the two devices has small variation. The above analysis shows that there is a good consistency between the non-invasive monitoring value of the test equipment and the invasive test results of the blood gas analysis equipment. The linear regression analysis was made on the changes of the test instrument monitoring value and blood gas analysis detection value. The fitting linear equation was △rSO2=-0.98+0.93△Sa/vO2, and the slope was 0.93, which was close to 1. The regression line was close to the 45° diagonal trend. The correlation coefficient of trend changes of the two equipment is 0.95, indicating that the change trend of the test equipment and blood gas analyzer has a good correlation. Analyze the trend changes value, due to the variation of every subjects is relative to the first platform first blood gas analysis values as the base to calculate, so the data points less than 10 absolute value analysis, the test equipment and the trend of blood gas analysis change the average deviation is 0.32%, the standard deviation is 2.97%, RMS very different trend is 2.97%, The clinical evaluation standard of trend Arms≤5% was met. ConclusionThere is good correlation and consistency between the test instrument monitoring value and the absolute value of blood gas analyzer.Trial Registration: The study has been retrospectively registered in Chinese Clinical Trial Registration with the registration number ChiCTR2100052321, date of registration 24/10/2021.