A Physical Model of the Human Systemic Arterial Tree

Abstract

A physical model of the human arterial tree has been developed to be used in a computer controlled mock circulatory system (MCS). Its aim is to represent systemic arterial tree properties and extend the capacity of the MCS to intraortic balloon pump (IABP) testing. The main problem was to model the aorta simply and to accurately reproduce aortic impedance and related flow and pressure waveforms at different sections. The model is composed of eight segments; lumped parameter models are used for its peripheral loads. After the numerical simulation, the physical model was reproduced as a silicon rubber tapered tube. This rubber was chosen for its stability over time and the acceptable behaviour of its Young's modulus (Ey = 22.23 gf x mm(-2)) with different loads and in comparison with data from the literature (Ey approximately 20.4 gf x mm(-2)). The properties of each segment of the aorta were defined in terms of compliance, resistance and inertance as a function of length, radius and thickness. The variable thickness was obtained using positive and negative molds. Total static compliance of the aorta model is about 1.125 x 10(-3) g(-1) x cm4 x sec2 (1.5 cm3 x mmHg(-1)). Measurements were performed both on numerical and physical models (in open and closed loop configuration). Data reported show pressure and flow waveforms along with input impedance modulus and phase. The results are in good agreement with data from the literature.

Analysis of the Effect of Ageing on Rising Edge Characteristics of the Photoplethysmogram using a Modified Windkessel Model

“…To take the flow inertia of the blood mass into account, Burattini and Gnudi (1982) included an inertia part (inductance) in series or parallel to the series resistance. In various publications these circuits were then used as the basic blocks in building complex systems to describe the systemic blood flow through the heart, organs and supplying vessels (Geertsema et al 1997;Ferrari et al 2000).…”

Numerical analysis of different cardiac functions and support modes on blood damage potential in an axial pump

“…The steady-state pressure rise and flow rate ( H−Q ) characteristics was calculated by CFD and polyfitted into the LPM. The inertia L ca and resistance R ca of the fluid in inlet and outlet cannula are calculated according to the formula 14 :…”

Potential nonlinear behaviour with VAD use in humans

“…Nonlinearities in the arterial system stem from the pressure-volume relationship of the wall. Detailed treatments of the arteries can include upw ards of eight segments, to al low for the variation in arterial diameter, and can be developed using the Navier-Stokes equations (Kuklinski et al, 1984), or using hydraulic principles (Ferrari et al, 2000). The traditional arterial model is know n as the Windkessel model, bu t in many cases the threeelement Windkessel model has been superseded by more detailed, nonlinear treatments of the arterial system (Li et al, 1990).…”

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