Computer identification of models for the arterial tree input impedance: Comparison between two new simple models and first experimental results

1982 ◽  
Vol 20 (2) ◽  
pp. 134-144 ◽  
Author(s):  
R. Burattini ◽  
G. Gnudi
Keyword(s):  
Input Impedance ◽  
Experimental Results ◽  
Arterial Tree ◽  
Computer Identification ◽  
Simple Models

NUMERICAL SIMULATION AND VALIDITY OF A NOVEL METHOD FOR THE PREDICTION OF ARTERY STENOSIS VIA INPUT IMPEDANCE AND SUPPORT VECTOR MACHINE

2014 ◽  
Vol 26 (01) ◽  
pp. 1450002 ◽  
Author(s):  
Hanguang Xiao
Keyword(s):  
Support Vector Machine ◽  
Input Impedance ◽  
Recursive Algorithm ◽  
Artery Stenosis ◽  
Support Vector ◽  
Arterial Tree ◽  
Novel Method ◽  
The Mean ◽  
Fold Cross Validation ◽  
Systemic Arterial Tree

The early detection and intervention of artery stenosis is very important to reduce the mortality of cardiovascular disease. A novel method for predicting artery stenosis was proposed by using the input impedance of the systemic arterial tree and support vector machine (SVM). Based on the built transmission line model of a 55-segment systemic arterial tree, the input impedance of the arterial tree was calculated by using a recursive algorithm. A sample database of the input impedance was established by specifying the different positions and degrees of artery stenosis. A SVM prediction model was trained by using the sample database. 10-fold cross-validation was used to evaluate the performance of the SVM. The effects of stenosis position and degree on the accuracy of the prediction were discussed. The results showed that the mean specificity, sensitivity and overall accuracy of the SVM are 80.2%, 98.2% and 89.2%, respectively, for the 50% threshold of stenosis degree. Increasing the threshold of the stenosis degree from 10% to 90% increases the overall accuracy from 82.2% to 97.4%. Increasing the distance of the stenosis artery from the heart gradually decreases the overall accuracy from 97.1% to 58%. The deterioration of the stenosis degree to 90% increases the prediction accuracy of the SVM to more than 90% for the stenosis of peripheral artery. The simulation demonstrated theoretically the feasibility of the proposed method for predicting artery stenosis via the input impedance of the systemic arterial tree and SVM.

A Hybrid Mock Circulatory System: Development and Testing of an Electro-hydraulic Impedance Simulator

2003 ◽  
Vol 26 (1) ◽  
pp. 53-63 ◽  
Author(s):  
M. Kozarski ◽  
G. Ferrari ◽  
F. Clemente ◽  
K. Górczyńska ◽  
C. De Lazzari ◽  
...  
Keyword(s):  
Input Impedance ◽  
Numerical Models ◽  
Peripheral Resistance ◽  
Left Ventricular ◽  
Physical Models ◽  
Gear Pump ◽  
Arterial Tree ◽  
Windkessel Model ◽  
Mock Circulatory System ◽  
Hydraulic Impedance

Mock circulatory systems are used to test mechanical assist devices and for training and research purposes; when compared to numerical models, however, they are not flexible enough and rather expensive. The concept of merging numerical and physical models, resulting in a hybrid one, is applied here to represent the input impedance of the systemic arterial tree, by a conventional windkessel model built out of an electro-hydraulic (E-H) impedance simulator added to a hydraulic section. This model is inserted into an open loop circuit, completed by another hybrid model representing the ventricular function. The E-H impedance simulator is essentially an electrically controlled flow source (a gear pump). Referring to the windkessel model, it is used to simulate the peripheral resistance and the hydraulic compliance, creating the desired input impedance. The data reported describe the characterisation of the E-H impedance simulator and demonstrate its behaviour when it is connected to a hybrid ventricular model. Experiments were performed under different hemodynamic conditions, including the presence of a left ventricular assist device (LVAD).

Normalized input impedance and arterial decay time over heart period are independent of animal size

1991 ◽  
Vol 261 (1) ◽  
pp. R126-R133 ◽  
Author(s):  
N. Westerhof ◽  
G. Elzinga
Keyword(s):  
Heart Rate ◽  
Decay Time ◽  
Input Impedance ◽  
Diastolic Pressure ◽  
Arterial Compliance ◽  
Characteristic Impedance ◽  
Peripheral Resistance ◽  
Arterial System ◽  
Heart Period ◽  
Arterial Tree

The arterial system of mammals in the weight range from 0.6 to 70 kg is characterized by the three-element windkessel, a succinct representation of the arterial tree consisting of the parameters peripheral resistance (Rp), total arterial compliance (C), and aortic characteristic impedance (Zc). The values of these parameters in resting conditions are related to body mass (M). The time constant, or decay time (tau), of the arterial system (defining rate of decay of aortic pressure in diastole), the product of Rp and C, is also evaluated. The dependencies of the heart period (T, inverse of heart rate), and durations of ejection (Ts) and of diastole (Td) in resting conditions are also determined as a function of M. It is found that Rp = Rp0M-0.93; Zc = Zc0M-0.97; and C = C0M+1.23, where Rp0, Zc0, and C0 are proportionality constants. Zc is thus a constant fraction of Rp in all mammals. tau is related to M as tau = tau 0M+0.29; T and Td are related to M as T = T0M+0.27 and Td = Td0M+0.30, where tau 0, T0, and Td0 are proportionality constants. The duration of diastole is thus a constant fraction of T, and the ratios T/tau and Td/tau are independent of M. The findings indicate that arterial input impedance, normalized to aortic Zc and plotted as a function of frequency normalized to heart rate, is similar for all mammals. The finding that the ratio Td/tau is the same in mammals (and Ts/T and stroke volume/M are constant) explains the constancy of pulse pressure (systolic minus diastolic pressure).(ABSTRACT TRUNCATED AT 250 WORDS)

Scatter in input impedance spectrum may result from the elastic nonlinearity of the arterial wall

1995 ◽  
Vol 269 (4) ◽  
pp. H1490-H1495 ◽  
Author(s):  
N. Stergiopulos ◽  
J. J. Meister ◽  
N. Westerhof
Keyword(s):  
Elastic Properties ◽  
Input Impedance ◽  
Arterial Wall ◽  
Impedance Spectrum ◽  
Arterial Tree ◽  
Heart Rates ◽  
Aortic Input Impedance ◽  
Nonlinear Elastic ◽  
Phase Angles ◽  
Wave Shapes

We have examined the role of the nonlinear elastic properties of the arterial wall on the human aortic input impedance obtained at different heart rates and different pressure and flow wave shapes. Pressure and flow were taken from a computer model that provides realistic simulations of the nonlinear distributed systemic arterial tree. Different wave shapes of ascending aorta pressure and flow and different heart rates were used to derive input impedance moduli and phase angles via Fourier analysis. The results show that the nonlinear elastic properties of the arterial wall are responsible for significant variations in the input impedance spectrum when changes in heart rate and aortic flow wave shape take place. This finding may explain the scatter often observed in experimentally determined input impedance data using different heart rates obtained by pacing.

Input Impedance of the Canine Coronary Arterial Tree

1990 ◽  
pp. 99-108
Author(s):  
Nico Westerhof ◽  
Pieter Sipkema
Keyword(s):  
Input Impedance ◽  
Arterial Tree

Port Interchange in Voltage Mode Current Conveyor Based Filters

1997 ◽  
Vol 07 (06) ◽  
pp. 543-561 ◽  
Author(s):  
Ahmed M. Soliman
Keyword(s):  
Input Impedance ◽  
Transformation Method ◽  
Current Conveyor ◽  
Experimental Results ◽  
High Input ◽  
High Input Impedance ◽  
Pspice Simulations ◽  
Voltage Mode

A transformation method which leads to the generation of high input impedance current conveyor based filters from finite input impedance circuits is given. Applications of the transformation method are included. PSpice simulations and experimental results indicating the performance of the transformed current conveyor circuit compared with the original circuit are also given.

scholarly journals Elastic follow-up and relaxation of residual stresses

2010 ◽  
Vol 224 (4) ◽  
pp. 777-787 ◽  
Author(s):  
D J Smith ◽  
J McFadden ◽  
S Hadidimoud ◽  
A J Smith ◽  
A J Stormonth-Darling ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Experimental Results ◽  
Test Rig ◽  
Reliable Measure ◽  
Initial Residual Stress ◽  
Series Of Experiments ◽  
Different Levels ◽  
Simple Models

A series of experiments were undertaken using a multiple bar assembly to measure elastic follow-up and relaxation of an initial residual stress. A test rig was designed to permit different levels of elastic follow-up to occur. The general features of the experimental results confirmed predictions provided by simple models. The most reliable measure of elastic follow-up was obtained by measuring the relaxation of the initial residual stress. The rate of relaxation of the residual stress is found to be proportional to the elastic follow-up factor.

NUMERICAL SIMULATION OF HUMAN SYSTEMIC ARTERIAL HEMODYNAMICS BASED ON A TRANSMISSION LINE MODEL AND RECURSIVE ALGORITHM

2012 ◽  
Vol 12 (01) ◽  
pp. 1250020 ◽  
Author(s):  
WEI HE ◽  
HANGUANG XIAO ◽  
XINGHUA LIU
Keyword(s):  
Blood Pressure ◽  
Transmission Line ◽  
Input Impedance ◽  
Recursive Algorithm ◽  
Ascending Aorta ◽  
Transmission Line Model ◽  
Arterial Tree ◽  
Line Model ◽  
Arterial Hemodynamics ◽  
Flow Waveforms

A novel recursive algorithm was proposed to calculate the input impedance of human systemic arterial tree, and to simulate the human systemic arterial hemodynamics with an 55 segment transmission line model. In calculation of input impedance, the structure of the arterial tree was expressed as a single linked list. An infinitesimal constant was used to replace 0 Hz frequency to calculate the DC and AC part of input impedance simultaneously. The input impedance at any point of the arterial tree can obtain easily by the proposed recursive algorithm. The results of input impedance are in accord with experimental data and other models' results. In addition, some comparisons were conducted about the effects of arterial compliance, length, internal radius and wall thickness on the input impedance of ascending aorta. The results showed input impedances of ascending aorta displayed significantly different characteristics for different kinds of parameters. Finally, the blood pressure and flow waveforms of all arterial segments were calculated and displayed in 3D. The arterial elasticity and viscosity were discussed by changing the Young's modulus and the phase difference, respectively. The simulation results showed that the blood pressure and flow waveforms of the arterial tree reflected accurately the main characteristic features of physiopathological changes, which demonstrated the effectiveness of the proposed model.

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