A LabVIEW™ Model Incorporating an Open-Loop Arterial Impedance and a Closed-Loop Circulatory System

Abstract

While numerous computer models exist for the circulatory system, many are limited in scope, contain unwanted features or incorporate complex components specific to unique experimental situations. Our purpose was to develop a basic, yet multifaceted, computer model of the left heart and systemic circulation in LabVIEW having universal appeal without sacrificing crucial physiologic features. The program we developed employs Windkessel-type impedance models in several open-loop configurations and a closed-loop model coupling a lumped impedance and ventricular pressure source. The open-loop impedance models demonstrate afterload effects on arbitrary aortic pressure/flow inputs. The closed-loop model catalogs the major circulatory waveforms with changes in afterload, preload, and left heart properties. Our model provides an avenue for expanding the use of the ventricular equations through closed-loop coupling that includes a basic coronary circuit. Tested values used for the afterload components and the effects of afterload parameter changes on various waveforms are consistent with published data. We conclude that this model offers the ability to alter several circulatory factors and digitally catalog the most salient features of the pressure/flow waveforms employing a user-friendly platform. These features make the model a useful instructional tool for students as well as a simple experimental tool for cardiovascular research.

Contribution of the Arterial System and the Heart to Blood Pressure during Normal Aging – A Simulation Study

“…The model parameters for a normal 20 years old adult were chosen in order to reproduce physiological pressure and flow curves. The arterial model parameters at this age were C = 2.8 mL/mmHg, R = 0.8 mmHg∙s/mL, Z c = 0.02 mmHg∙s/mL and L = 0.005 mmHg∙s 2 /mL [ 9 , 15 ]. C and R were varied with age during simulations (for each decade between 20 and 80 years, see below), Z c was varied in proportion to 1/ [ 9 ] and L was kept constant for all ages.…”

The Donders Model of the Circulation in Normo- and Pathophysiology

“…In essence, their model contains the blood conducting pathway, vascular stress and relaxation as it affects circulatory pressure, membrane dynamics of the capillaries, tissue fluid volume and pressure, electrolyte shift, angiotensin, aldosterone, and antidiuretic hormone control, kidney dynamics, control of blood flow in muscle, autoregulation, autonomic control as well as a number of other control facets. After a period of introspection, attention turned to focus on refining the quality of models (Cole et al 2005), especially regarding the cardiac chambers (Palladino et al 2000a) and on rethinking the strategy of model making in physiology, in particular with respect to predicting functions from structure and structure from function (Palladino et al 2000b). …”

Mechanical Models of Artery Walls

“…In [26] various open loop and closed loop circuits are analyzed and they are shown to express accurately aortic mean pressure and flow data, similarly in [28] the closed loop simulation results are positively verified by comparison with the pressure and flow data from human aorta. In [117] open loop model is shown to give results that comply with pressure and flow in human aorta and brachial and femoral arteries.…”

“…(Possibly branching) sequence of segments can be terminated with a terminal resistance or Windkessel or looped to form the model of the whole system (see [26,28,117]). Example of the sequence that models the artery bifurcation is shown in the Fig.…”