Research On Tissue Oxygen Saturation Monitoring Technology For Adaptive Local Tissue Regions

Tissue oxygen saturation is the average oxygen saturation of haemoglobin in all red blood cells of a local tissue and can be used to assess the oxygen delivery and uptake capacity in the tissue,reflecting the normal function of tissue microcirculation and tissue metabolism,and is an important physiological parameter of human tissue.Tissue oxygen saturation needs to be measured for post-operative rehabilitation monitoring of skin flap transplants,scientific evaluation of the effect of bougie exercise on the circulation of diabetic feet and monitoring of oxygen saturation of brain tissue in order to obtain information about the physiology and pathology of the tissue and to take appropriate and effective therapeutic measures.Therefore,real-time monitoring of tissue oxygen saturation is of great research importance.Based on the theoretical basis of NIR spectroscopy to measure physiological parameters,the theoretical algorithm of tissue oxygen saturation based on modified Beer-Lambert law(MBLL)and spatially resolved spectrum(SRS)based on the steady-state transport equation of photons was investigated,and an adaptive tissue oxygen saturation algorithm was proposed.The principle prototype system was developed,and tissue homogeneity validation experiments and venous blockage experiments were carried out on several volunteers’ forearms.The main research work of the thesis is as follows.(1)In order to solve the problem of assuming tissue homogeneity,a least squares based adaptive tissue oxygen saturation monitoring scheme for local tissue regions is proposed,a method for evaluating local tissue homogeneity based on MBLL is analysed and Monte Carlo simulation experiments are carried out.The results show that compared to the SRS algorithm,the adaptive tissue oxygen saturation algorithm for local tissue regions has a mean square error in calculating tissue oxygen saturation was reduced by approximately 1.3 and had higher accuracy in calculating tissue oxygen saturation.(2)In order to solve the problem that tissue oxygen meter probes need to be designed separately for the different tissues to be measured,a threewavelength twelve-detector tissue oxygen meter probe structure design scheme was proposed,a tissue oxygen saturation principle prototype system was developed,and forearm tissue homogeneity verification experiments and venous blockage experiments were conducted on several volunteers.The experimental results show that:in the case of constant tissue oxygen saturation,the optimal homogeneous region of forearm tissue varies between 26.424 mm and 70.986 mm for different volunteers;in the case of varying tissue oxygen saturation,the optimal homogeneous region of forearm tissue changes from 33.851 mm-63.559 mm to 41.278 mm-70.986 mm for 840 nm NIR light for the same volunteers.The adaptive local tissue oxygen saturation algorithm proposed in the thesis can overcome the above problem of the change in the optimal homogeneous region of the tissue to be measured,and the principle prototype system developed can monitor the change in tissue oxygen saturation in real time.(3)In order to solve the problem of detector redundancy in the design process of multi-detector probes,based on the analysis of experimental data on venous blocking,a strategy for matching the distance between light source and detector in tissue oximeter probes is proposed:the threshold for light intensity change is set during the change of tissue oxygen saturation where the tissue to be measured,and the detector position greater than this threshold is used as the effective matching position between light source and detector in the probe design.Based on the proposed strategy,the effective matching distance between the light source and the detector in the probe is between 18.997 mm and 70.986 mm,reducing the cost of the probe production by decreasing the number of redundant detectors in the multi-detector probe.