Research On Noninvasive Measurement Of Venous Blood Oxygen Saturation

Sv O2, blood oxygen saturation after capillary microcirculation,(venous blood oxygen saturation) is the oxyhemoglobin in the ratio of total hemoglobin of vein. Compared with the supply power of oxygen-Sa O2(arterial blood oxygen saturation), venous oxygen saturation represents the organic consumption power. And reflecting the respiration circulation of human and oxygen consumption, as it’s closely related to Sa O2, Hemoglobin, and CO(Cardiac Output),Sv O2 has a great meaning in evaluate the health of patients.Pulse oximetry, as a noninvasive, continuous device for Sa O2, is wildly applied in clinic. However, there still exists no noninvasive or continuous device for measuring Sv O2 in market. And because of the risk and inconvenience of using invasive method in measuring Sv O2, most of the time we evaluate the oxygen consumption of patients by the experience of doctor. But the oxygen consumption depends both on people, environment, and organ, and it is hardly to estimate such parameter simply by experience.To making measure Sv O2 noninvasively and continuously, on the basis of measuring pulse oxygen saturation, we proposed a new method to collecting venous photoplethismograpyh signal to measuring localized Sv O2. And by taking venous disturbance as a useful signal, which is a moving disturbance noise for measuring Sp O2(pulse oxygen saturation), we build a stimulate system to produce stable moving disturbance to enhancing venous signal. And under the test of hypoxic experiment, our hardware, software, and algorithm system successfully collected venous signal and turn it into Sv O2.Experimental results showed that our method successfully enhanced venous signal without interfere normal Sp O2 measuring. And our Sv O2 is approximately reflects the venous oxygen saturation decreasing progress during hypoxic experiment. The RMSE(root mean square error) of Sp O2 after calibration between reference device and ours is approximately 0.845, correlation coefficient of Sp O2 after calibration between reference device and ours is approximately 0.997, RMSE of Sv O2 without calibration between reference device and ours is approximately 7.75, oxygen consumption between reference device and ours is approximately 2.47. And, on some cases, we found the localized Sv O2 has some connection with localized PI(Perfusion Index)that it would rising or reducing in the same trend as PI.