Research On Thoracic Bioimpedance For Cardiac Hemodynamic Analysis

Currently,these approaches for cardiac hemodynamic analysis have been developed from invasive ways,minimal invasive methods to non-invasive methods.Doppler echocardiography and thoracic bio-impedance methods as major non-invasive ways are applied.The latter is easier to operate and measure cardiac function,what’s more,it can monitor continuously for a long time.But thoracic bio-impedance technology has not been so mature,and there are some troubles such as questioned measurement accuracy,poor robustness and so on.Therefore,how to improve the measurement precision in thoracic bio-impedance method to make its clinical value function better is the urgent problem to be solved.These following jobs have been done for the trouble:1.Based on the thoracic bio-impedance technology,this paper introduces research contents of cardiac hemodynamic,the physiological meaning of each hemodynamic parameter,and application of these parameters in clinics.2.Physiological mechanism for the calculation of cardiac hemodynamic parameters in thoracic bio-impedance are presented and signify that whether feature points of electrocardiogram and impedance cardiography signals can be detected precisely is the precondition of the accurate calculation of hemodynamic parameters.3.The algorithm combined adaptive ensemble empirical mode decomposition with wavelet thresholding are designed to denoise electrocardiogram and impedance cardiography signals to ensure the precise detection of their feature points.4.Specific signals in particular layers from electrocardiogram or impedance cardiography signal decomposed are selected as detection layers to recognize feature points of both signals according to different frequency ranges of specific layers of electrocardiogram and impedance cardiography,combining with difference and adaptive segmentation.Verification results show that accurate recognition rates of QRS,T and P waves are respectively 99.94%,99.86% and 99.75% for electrocardiogram signal,and accuracy rate of beat detection of impedance cardiography signal is 99.72% as a whole,which are superior to algorithms at present.5.This paper discusses the calculation of hemodynamic parameters and designs a GUI to present feature point detection results of signals and hemodynamic parameters and takes part of cases with different cardiac diseases as example to testify and demonstrate their clinical significance of those parameters calculated.In addition,in this paper,to validate a good consistency of ejection fraction calculated by two non-invasive methods,thoracic bio-impedance and doppler echocardiography methods,where the latter is applied extensively in clinic.Bland-Altman consistency analysis is taken and the result shows that the algorithms proposed is reliable,which is used to analyze cardiac hemodynamic parameters.