Study On Tissue Oxygen Saturation Monitoring System By Near Infrared Spectroscopy

Oxygen is an important living substance in human body,and it is the basis of maintaining normal function of tissues and cells in vivo.Oxygen exists mainly in the form of binding with hemoglobin in the blood.Oxygen saturation can reflect the combination of oxygen and hemoglobin,and judge the ability of blood transportation.It is a physiological index in clinical diagnosis.Tissue oxygen saturation is the average blood oxygen parameter of microvessels in tissues.It can reflect the oxygen and blood supply of tissues and organs more carefully.It also has more important reference value in clinical diagnosis.However,the current mature technology can only measure the relative amount of tissue oxygen parameters,and the monitoring of tissue oxygen saturation parameters is still lack of effective means.The aim of this paper is to develop a non-invasive,continuous and real-time monitoring system of tissue oxygen saturation by near infrared spectroscopy.The existing theories of oxygen saturation measurement and relative measurement of hemoglobin concentration are analyzed.The optical properties of human tissues and the diffuse equation in biological tissue optics are discussed.A scheme for noninvasive measurement of tissue oxygen saturation is proposed and the calculation method of absolute quantity is studied.The measurement system is constructed by multi-module combination.The system includes sensor module,LED driver module,AD conversion module,weak signal amplification module and control module.In the design of the sensor module,the performance,advantages and disadvantages of the mainstream optical biosensor chip are compared,and the schemes based on different optical biosensors are designed.The feasibility of each scheme is analyzed and the sensor test is made.The main characteristics of the core chips of other modules are introduced,and a new I-V conversion scheme is proposed and the experimental data are verified.The design scheme of 900 analog front-end replacing control circuit is presented.Some schematic diagrams and package diagrams are given and the feasibility of this scheme is discussed.On the basis of the completion of the hardware system,the software design is carried out.The design ideas and some codes of LED timing control program,AD conversion program and serial communication program are described in this paper.The software program of the host computer is designed and compiled.The software has the functions of applying each sensor module,displaying light intensity data in an all-round way and displaying test results continuously.Non-invasive,real-time and continuous monitoring of tissue oxygen saturation was realized.In terms of system software,the light source timing control program,AD sampling program and human-computer interaction program are designed.The software program of the host computer is designed and compiled.The software has the functions of applying each sensor module,displaying light intensity data in an all-round way and displaying test results continuously.Non-invasive,real-time and continuous monitoring of tissue oxygen saturation was realized.Credibility validation experiment and forearm venous occlusion simulated skin flap embolization experiment were carried out with the system.The results showed that the same subjects were continuously measured,and the test results were stable.There were slight differences between different subjects,the difference was about 0.05.Under venous occlusion,the system tissue oxygen parameters changed significantly,with a maximum decrease of 0.25.Experiments show that the system has high stability and sensitivity.It can measure oxygen saturation parameters in real time and non-invasively and reflect the trend of tissue oxygen change.It can provide important basis for clinical detection of oxygen transport status of skin flaps after operation.