Development Of Noninvasive Cardiac Output Detection System Based On Thoracic Impedance Method

Cardiovascular disease has become one of the major disease threat to human life and health in recent years,cardiac output is an important index for evaluating cardiovascular status,monitoring hemodynamic parameters,such as cardiac output,has significant impacts on clinical practice.The thoracic impedance cardiac output measurement method is non-invasive,safe,and has rich and comprehensive parameter information,which also has low detection cost and simple operation.It can help the doctor in diagnosis,treatment,and medication,save the patient’s life,reduce patient’s pain,which is a monitoring technology with good market prospect.This article has developed an integrated system based on thoracic impedance method for cardiac output and related hemodynamic parameters.The first chapter introduces the various methods of cardiac output monitoring firstly,compares the advantages and disadvantages of those methods,and explains the domestic and overseas development status of thoracic impedance technology,which also includes the topic significance and innovation.In the second chapter,the principle and model of cardiac impedance measurement using thoracic impedance method are introduced in detail,the calculation formulas are deduced.The research progress of the new model is introduced,followed by the physiological significance of signal feature points,pointing out the factors that affect the measurement results.The third chapter is the hardware design of the system,and introduces the various hardware components,and the three measuring modules of ECG,cardiac impedance and respiration were introduced in detail..The fourth chapter introduces the lower computer driving software,upper computer monitoring platform,filter algorithm design and signal feature point detection.The functions of lower computer software include system self-check,incentive control,signal acquisition and preprocessing,and data transmission.The functions of upper computer monitoring platform include signal processing,feature point detection,parameter calculation,waveform and calculation result display,and data storage.The filter algorithm part focuses on the principle and solution of the adaptive filtering method to eliminate respiratory noise.The signal feature point detection section introduces the detection method of feature points in the ECG and cardiac impedance differential signals of the system.The fifth chapter introduces the system verification method and scheme,verification results and discussion.Eighteen hemodynamic related parameters were obtained by direct and indirect input calculation of the system,realizing continuous monitoring of hemodynamic parameters in real time.Thirty volunteer data were collected by using this system,and the accuracy comparison of 15 volunteers’data was conducted by using ICON^TM,a product sold on the market.The overall average error of stroke volume SV is 3.67 mL,the root mean square error is 7.13 mL,the overall mean error of cardiac output CO is 0.23 L,and the root mean square error is 0.72L,which verifies the feasibility of this system.The results show that the expected goals of the system are achieved,but the accuracy needs to be further improved.Finally,this paper summarizes the shortcomings of the system,puts forward the improvement methods and goals,and sets up a solid foundation for the improvement of the forthcoming system.