A Research Of Noninvasive Monitoring Technology And Device On Tissue Blood Oxygen Content

Sufficient oxygen supply is the basis of survival to all the lives. As an important parameter that reflects the physiological condition of human being, the blood oxygen content in tissues needs to be detected continually and at least one invasive method is in use. Not only does the conventional invasive measurement make patients painful, but also it is hard to realize the continue monitoring. Now the method that uses near infrared spectrum to detect the blood oxygen content has aroused the interest of scientists, though, there have not been sophisticated commercial instruments on market yet because of the weakness of signals of blood oxygen content and the randomness of photons diffusion. At first, this paper theoretically demonstrates the technology of the detection of blood oxygen content. Referring to the Monte Carlo simulation data and based on Lambert-Beer Law, this paper deduced the mathematical relation between the three variables of oxidized and deoxidized hemoglobin concentrations and the light intensity strayed from tissue. In addition, the paper discusses the research and development of the detection system. Considering the weakness and low-frequency of blood oxygen concentration signal, a new type lock-in amplifier(LIA) detecting circuit is suggested to detect the variety of blood oxygen concentration , after theoretically analyzing the principle of conventional LIA and the characteristic of over-sampling and integration of Σ-ΔA/DC. This circuit is an innovation for the LIA circuit structure, being compact and easy to be realized. It is better in performance than conventional LIA, at which experiment results have proved. In addition, compared to the conventional digital LIA, this circuit does not need any high-speed microprocessor. It receives and transfers data from/to Micro-Processing Unit (MPU) seamlessly. Compared to the existing blood oxygen detectors, the one suggested in this paper first adopts MSC1212 withΣ-ΔA/DC integrated as the core of the new detector, which has simplified the system structure and intensified the system anti-interference ability. Also this paper provides the hardware design and software implementation of all parts of the detector including sampling sensor, signal detecting parts and signal processing parts. At last, the paper demonstrates the stability, sensitivity and compatibility with the theoretical analysis through the experiments and data processing.