An In Vitro Circulatory System For Simulating Blood Flow Electrical Impedance Of Common Carotid Artery

Hypertension and atherosclerosis are the risk factors of cardiovascular and cerebrovascular diseases.The occurrence of hypertension and atherosclerosis is usually accompanied by a series of changes in hemodynamic parameters,which are usually earlier than those changes of imaging parameters.Since the common carotid artery is an important blood supply organ that gathers the blood flow information of the upstream aorta and the downstream cerebrovascular bed,the detection of its hemodynamic parameters has important clinical significance for the early diagnosis of cardiovascular and cerebrovascular diseases.The traditional Doppler ultrasound detection of common carotid artery hemodynamic parameters is high precision,but it also has the disadvantages of expensive equipment and complicated operation.Bioelectrical impedance technology can overcome these disadvantages,but the quantitative relationship between blood flow impedance and hemodynamic parameters remains to be further investigated.Since the common carotid artery system is affected by the respiratory system,the nervous system and other systems,an in vitro circulatory system that can simulate blood flow electrical impedance of common carotid artery blood flow is strongly needed in order to provide an experimental platform for the in-depth study of the quantitative relationship between the electric impedance signal and the hemodynamic parameters.In this paper,firstly,the blood flow velocity and the diameter of the common carotid artery were measured by Doppler ultrasound,and the blood flow electrical impedance of the common carotid artery was calculated combining the Womersley theory of pulsatile flow and the Maxwell-Fricke theory of blood conductivity,which is found that blood flow electrical impedance is affected by both vascular diameter and blood flow velocity.Then,based on a five-element elastic cavity model,an in vitro circulatory system simulating the blood flow electrical impedance of the common carotid artery was constructed.The system is mainly composed of a centrifugal pump simulating the pumping function of heart,an elastic chamber simulating vascular compliance,a resistance valve simulating blood flow resistance,an elastic tube simulating artery and a rigid tube compared with the elastic tube.Finally,the blood pressure,pressure drop and blood flow electrical impedance detection system consisted of the pressure sensors and the impedance measurement system achieves the acquisition of pressure waveform and the accurate measurement of dynamic blood flow electrical impedance.Meanwhile,the control of frequency and working energy level of the centrifugal pump is achieved by the STM32 controller.The in vitro circulatory system of common carotid artery blood flow can simulate arterial blood flow impedance signal under different physiological conditions as needed,by changing the frequency and working energy level of centrifugal pump,the blood flow electrical impedance signal at different heart rate and blood flow velocity can also be simulated.It is concluded that the in vitro circulatory system can simulate the influence factors of blood flow impedance of the common carotid artery,namely the change of blood vessel diameter and blood flow velocity,it can also detect the corresponding change of blood flow impedance.Therefore,this in vitro circulation system can be used as an experimental platform and lays a foundation for the in-depth study of the quantitative relationship between the electric impedance signal and the hemodynamic parameters.