A Study Of Self-adaptive Method For The Reconstruction Of Central Aortic Pressure Using Continuous Peripheral Arterial Blood Pressure

According to China Cardiovascular Diseases Report of 2018 released by China’s National Center for Cardiovascular Diseases,the prevalence of cardiovascular diseases is still on the rise in China.Hypertension is the foremost risk factor for cardiovascular and cerebrovascular diseases,so monitoring and managing blood pressure(BP)is of great significance in reducing the incidence of such diseases.Studies have shown that patients’ central aortic pressure(CAP)is closely related to their incidence of cardiovascular disease,and the waveform of the CAP contains a great deal of hemodynamic information.Accurate and continuous monitoring of CAP is the key element for treating and managing cardiovascular disease,especially hypertension.Existing methods for estimating continuous CAP waves,such as the general transfer function method,are all based on clinical experiments and experience,but lack a systematic theoretical basis and are simply general methods which cannot exclude the influence of individual cardiovascular differences on the results of the estimation.Other alternatives,such as the gold standard invasive measurement method,include problems such as poor operability and high risk of infection.Therefore,it is necessary to establish an individualized non-invasive continuous BP measurement or estimation method.The vascular unloading technique(VUT)is currently the most widely used method for non-invasive continuous BP testing in clinical practice.The continuous BP measurement system based on this method is also the most commonly used continuous BP measurement device system in the medical technology field,but there are several major problems with these types of medical electronic devices: 1)It is impossible for them to accurately record individual BAP or even CAP.2)These devices cannot be made wearable,and are only suitable for bedside use.3)These devices are unable to intelligently recognize changes in the subjects’ physiological conditions,and cannot adopt corresponding calibration modes according to different types of physiological conditions.This paper includes an in-depth study of existing methods of calculating CAP and these systems’ key technical problems.The main research outcomes and contributions of this paper are as follows:1)This paper presents a new method of calculating CAP using dual peripheral BP.In the absence of blood flow information,the parameters of CAP should be estimated using prior knowledge of the traditional incident and reflected wave methods.In this paper,on the basis of the incident and reflected wave methods,a two-stage aortic hemodynamic model has been established,and the new model of measuring continuous peripheral BP has been used for making up for the lacking blood flow information,and continuous CAP has thus been able to be calculated.This two-stage aortic hemodynamic model is generally more able to be adapted to general public testing purposes than alternative models.2)In this paper,we use dual peripheral continuous BP signals and adaptive filtering system identification methods to solve for system parameters,which makes it possible to overcome measurement errors caused by finger vasoconstriction/vasodilatation and other problems,enabling the calculation algorithm to adapt to changes in vascular status.3)In this paper,an accurate method of calculating CAP is proposed which uses single peripheral BP measured using VUT method.Adapting to the characteristics of the VUT and the Newman method,we propose a method to non-invasively break down the blood flow at the end of the patient’s finger,without subjecting them to any trauma,to obtain the incident and reflected wave and thereby calculate the brachial arterial pressure(BAP),and even their CAP.For this method,a Windkessel model based on three parameters can be used to correct BP measurement errors caused by venous blockages,using the VUT and model derivation.The errors of the proposed method in estimating systolic and diastolic pressures of BAP are 1.9 ± 5.8 mmHg and-1.4 ± 5.0 mmHg,respectively.4)In this paper,we propose a date-driven method to adaptively reconstruct the BAP waves from the FAP waves and by using a two-level optimization strategy,an individualized transfer function based on multiple linear regressions can be derived from the subjects’ normal physiological parameters.The mean ± standard deviation of the root mean square errors between the reference BAP waves and the BAP waves reconstructed from FAP waves is 3.6 ± 2.2 mmHg.5)In this paper,a dual BP measurement platform is designed using measurement of BP in the patient’s radial arteries and finger arteries.In addition,a coordinated control method is designed for use with the subject’s finger arteries and radial arteries and in line with their individual physiological characteristics,so as to reduce the interaction between upstream and downstream BP measurements and to provide an accurate data basis for the calculation algorithm.6)This paper also includes the design for a wearable continuous BP measurement system based on VUT method.This system establishes a computational fluid dynamics model to obtain the minimum airflow and cylinder parameters required to reach the target airbag pressure.