Acoustic Detection Of Stenosis In Arterio Venous Access

Maintainable hemodialysis is an alternative treatment for patients with end-stage kidney disease,once used it will be a long-term,uninterrupted,cyclical process,unless the successful transplant of kidney,for this reason,Arterio Venous Access(AVA)is often likened to dialysis patients' "lifeline",and it needs to maintain good routine maintenance for reuseAs a pathological "physiological" structure,AVA are affected by the continuous action of hemodynamic environment,which will be narrowed by the growth of the inner wall(membrane),resulting in insufficient blood supply or even embolism,so it is necessary to continuously monitor it.Clinically,imaging examination method is the gold method of the diagnosis of stenosis in AVA,and physical examination methods such as acoustics and touch diagnosis are routine examination(screening)methods because of their non-invasion,effectiveness and convenience,which are also the basic skills that medical specialists engaged in hemodialysis and AVA must master.However,even for the specialists,to obtain specific judgments(e.g.stenosis)from this abnormal organizational structure by completing a standard,clinically-valuable physical examination requires systematic training,and more so on patients with limited knowledge and experience(hospitals usually demond on conducting simple home-based self-examinationat at least twice a week by training patients).Therefore,it is of practical significance to "objectiveize" and "digitalize" the physical examination methods such as acoustics and touch diagnosis of AVA.In summary,this study proposes the AVA stenosis detection method and digitalized system.The main content of this article is as follows: 1)Mathematical Modeling of AVA.Comb the basic knowledge of AVA's hemodynamics,on this basis,the centralized parameters modeling method is used to establish the elastic cavity model of the artery,AVA,the capillaries in the outside of the hand and vein on the arm,using the similarity between fluid and electrical theory,the equivalent circuit parameters model is established by means of capacitance,inductor and resistance representing hemodynamic parameters,and two main parameters including blood flow and blood pressure that are related to acoustic signal are discussed,so that the mechanism of change of the main parameters is more intuitive and easier to deal with.2)Biophysical simulation model design and implementation.In order to extract the acoustic signal features of AVA that associated with stenosis,the degree of stenosis should act as the controlled variable,however,clinical studies show that there are individual differences in other hemodynamic parameters than stenosis,what's more,it takes a long time measurement and a large amount of data to extract the features related to stenosis by clinically measured acoustic signals alone.Therefore,based on the circuit parameters model in preceding paragraph,a biophysical simulation model that simulates the AVA is built to highlight the features correlated with stenosis.Design each component of the model,and the component selection and system construction are completed.The experimental results show that the hemodynamic parameters in the physical simulation model are consistent with the clinical AVA,and the error is not more than 5%.3)Research on acoustic detection method.The stenosis detection method includes three steps:denoise and segmentation,feature extraction and classification.Acoustic signal is noisy and non-smooth,for this reason,using the A-weighted filtering method and Gaussian smoothing method for pre-processing.This paper extracts the features of the acoustic signal using the MUlti SIgnal Classification(MUSIC)spectral estimation method,which has high resultion for stenosis-related,high frequency,low energy signal,results shows the frequency peak near 820Hz(820±70Hz)correlates with stenosis.Meanwhile using supporting vector machines to classificate features into two categories,the accuracy of the proposed method on 19 clinically measured data sets was 84.2%,the MUSIC spectral estimation method improves the classification accuracy by 4%,compared with Autoregressive(AR)model and Wavlet method.4)Design the hardware system of electronic stethoscope.Finally,this study proposes the hardware system of electronic stethoscope for obtaining acoustic signals from Arterio Venous Access,it is verified by the software and hardware experiments together with the stenosis detection method proposed in this paper,and it is the basis for further development of the actual-used system.