Assessment Of Arterial Stiffness Based On The Effective Reflection Distance Theory And Single-channel Pulse Wave

In recent years,the impact of arterial stiffness on the cardiovascular is more and more of interest.The cardiovascular mortality rate is increasing year by year so that people pay more and more attention to the health of their cardiovascular systems.Through early detection of arterial stiffness,patients can get better treatment,which can bring great significance to human health.Pulse wave velocity measured from carotid artery to femoral artery can reflect the stiffness of aorta well,so carotid-femoral pulse wave velocity(cfPWV)is widely recognized as the "gold standard" in non-invasive clinical assessment methods.Unfortunately,this measurement process needs to expose the patient’s groin and the femoral artery is also difficult to locate,which make the method limited in practice.In order to overcomed these shortcomings,some researchers had proposed a new calculation method of aortic pulse wave velocity(aoPWV)based on single-channel pulse wave.Although this method did well in extracting the delay time of the reflected wave from the single-channel pulse wave,but it ignored the influence of age,height and some other factors on the effective reflection distance(ERD).Therefore,the accuracy in the calculation of aortic pulse wave velocity still needs to be improved.In this thesis,in order to improve the accuracy of aoPWV based on single-channel pulse,the ERD of pulse wave was fully investigated,and the new method of calculating aoPWV based on ERD theory and single-channel pulse signal was proposed.Based on the aortic pressure waves of 86 adult subjects(39.3±22.9 years),the constructed flow waves were established.Then the delay time was extracted after the aortic pressure wave was decomposed to the forward wave and the backward wave.Then,according to the synchronized collection of the carotid artery and the femoral artery,cfPWV was calculated.Finally,ERD can be calculated by the principle of pulse wave propagation and reflection.On the basis of these results,difference analysis showed ERD of old people(over 50 years)is significantly higher then the young(under 50 years)(p<0.05).Correlation analysis illustrated ERD was positive correlated with age(p<0.001),which meant the older the person,the longer the ERD.Stepwise multiple regression analysis showed that age and height were the independent factors of ERD,and then the regression equation was established.So through regression equation,ERD can be estimated based on age and height information.Then aoPWV based on single-channel pulse signal was calculated.In this thesis,Leave-One-Out method is used to verify the performance of the ERD model.Compared with the previous method,the aoPWV calculation method proposed in this thesis had higher linear correlation and better consistency with the "gold standard" cfPWV.The proposed method corrected the error of calculating aoPWV in older people.The analysis of correlation and uniformity further validated that the aoPWV calculated based on the effective reflection distance theory and single-channel pulse signal in this thesis achieved more accurate results in middle-aged and old people,improving the precision of assessing of arterial stiffness.