Study On Detection Of Abnoemal Blood Circulation And Evaluation Of Vascular Stenosis Based On LFOs

With the aggravation of aging population in China,the number of chronic vascular diseases continues to grow rapidly,which has become one of the important public health problems.Timely detection and evaluation of chronic vascular diseases is beneficial for patients to grasp their own disease situation at any time,and implement proper prevention and treatment measures in the best time to reduce the risk and degree of incidence.The related factor scoring is influenced by the subjectivity of the evaluator,and the clinical Ankle Brachial Index(ABI)detection is influenced by the patient’s heart beat,which leads to the deviation between the evaluation and the detection results.Although the existing angiography technology can accurately display vascular diseases,its technical complexity and application environment limitations are not conducive for patients to grasp their own diseases at any time.As a result,the function and analysis of Low Frequency Oscillations(LFOs)signals are introduced into the detection and evaluation of chronic vascular diseases,and the development of LFOs detection equipment,the propagation characteristics of LFOs and their application in the detection and evaluation of vascular diseases are deeply explored.Firstly,the key technologies of multi-channel LFOs detection were studied and the system was developed.Based on the structure of human peripheral distances,a nonmodulated,continuous wave and multi-channel light source signal detection principle based on Near Infrared Spectrum(NIRS)was proposed.A multi-channel communication circuit and a time-sharing transmission protocol were designed to control the synchronous transmission and orderly transmission of independent multi-channel signals.Cubic spline interpolation and kurtosis-based Wavelet Filtering(kb WF)were applied to remove the "spike" noise and continuous jitter noise respectively,which optimized the extraction of LFOs.What’s more,the equipment was developed and compared with the existing commercial equipment to verify the effectiveness and accuracy of the detection signal.Secondly,the law of LFOs transmission and its ability to reflect the changes of blood circulation were revealed.According to the characteristics of human structure and blood flow trend,the representative detection points of human peripheral LFOs were determined.Combined with the blood circulation and neurohumoral regulation cycle of healthy people,the detection time and interval parameters of LFOs were set,and an experimental scheme of LFOs detection with supine,fixed frequency and unilateral passive leg raising was put forward.The time-domain complexity,frequency-domain coherence,frequency-domain phase difference and spatial connectivity features of systemic LFOs were extracted by permutation entropy,coherence,phase shift and permutation mutual information methods.On this basis,compared with the resting-state LFOs detection experiments,the transmission law of LFOs with blood flow changes in different states was revealed,and the ability of LFOs to reflect the changes of blood circulation in healthy people in different states was determined.Thirdly,a symmetry deviation index method based on power spectrum estimation was proposed to reflect the symmetry difference of blood circulation in patients with vascular diseases by taking advantage of the characteristics that vascular diseases destroy the approximate symmetry propagation law of LFOs in the whole body,and combining with the action principle that vascular stenosis or occlusion limits the amplitude and affects the frequency of blood flow fluctuation.The clinical diagnosis results of patients with different types and degrees of vascular diseases were summarized,and the symmetry differences of systemic blood flow in patients with different types and degrees of vascular diseases were analyzed.On this basis,the applicable frequency band of LFOs to detect abnormal changes of blood circulation in different types and degrees of patients was revealed,and the advantages of distinguishing patients with different types and degrees of vascular diseases based on symmetry deviation index characteristics were clarified.Finally,an improved quadratic correlation weighted time delay estimation method based on passive leg raising was proposed to reflect the delay difference of LFOs caused by vascular stenosis in different propagation paths.The fluctuation of LFOs in blood vessels was modulated by the principle of passive leg raising to mobilize blood reflux,and the priority of LFOs signals on passive leg raising side was tested by Granger Causality Test.The relationships between different LFOs propagation pathways and vascular stenosis region and the relationships between the delay value of LFOs and the severity of vascular stenosis were analyzed by 0.05 Hz LFOs as biomarkers in passive leg raising.A method based on passive raising of left leg and passive raising of right leg was proposed to quickly evaluate the types of vascular stenosis areas in patients’ left lower limb,right lower limb or both lower limbs in a short time.