Characterization of an adult mock circulation for testing cardiac support devices.
ABSTRACT A need exists for a mock circulation that behaves in a physiologic manner for testing cardiac devices in normal and pathologic states. To address this need, an integrated mock cardiovascular system consisting of an atrium, ventricle, and systemic and coronary vasculature was developed specifically for testing ventricular assist devices (VADs). This test configuration enables atrial or ventricular apex inflow and aortic outflow cannulation connections. The objective of this study was to assess the ability of the mock ventricle to mimic the Frank-Starling response of normal, heart failure, and cardiac recovery conditions. The pressure-volume relationship of the mock ventricle was evaluated by varying ventricular volume over a wide range via atrial (preload) and aortic (afterload) occlusions. The input impedance of the mock vasculature was calculated using aortic pressure and flow measurements and also was used to estimate resistance, compliance, and inertial mechanical properties of the circulatory system. Results demonstrated that the mock ventricle pressure-volume loops and the end diastolic and end systolic pressure-volume relationships are representative of the Starling characteristics of the natural heart for each of the test conditions. The mock vasculature can be configured to mimic the input impedance and mechanical properties of native vasculature in the normal state. Although mock circulation testing systems cannot replace in vivo models, this configuration should be well suited for developing experimental protocols, testing device feedback control algorithms, investigating flow profiles, and training surgical staff on the operational procedures of cardiovascular devices.
Article: A complete mock circulation loop for the evaluation of left, right, and biventricular assist devices.[show abstract] [hide abstract]
ABSTRACT: A new mock circulation loop was developed to replicate the necessary features of the systemic and pulmonic circulatory systems, including pulsatile left and right ventricles coupled with vascular compliances and resistances. A brief description of the mock loop construction is provided before results are presented confirming the recreation of perfusion rates and pressures found in the natural systemic and pulmonic vascular trees for a normal and failing heart at rest. This rig provides the ability to evaluate the hemodynamic effect of left, right, and biventricular assist devices in vitro. The small and compact mock circulation rig has the potential to reduce device evaluation costs by simulating the natural circulatory system, thus providing valuable device performance feedback prior to expensive in vivo animal trials.Artificial Organs 08/2005; 29(7):564-72. · 2.00 Impact Factor
Conference Proceeding: Noninvasive Pulsatile Flow Estimation for an Implantable Rotary Blood Pump[show abstract] [hide abstract]
ABSTRACT: A noninvasive approach to the task of pulsatile flow estimation in an implantable rotary blood pump (iRBP) has been proposed. Employing six fluid solutions representing a range of viscosities equivalent to 20-50% blood hematocrit (HCT), pulsatile flow data was acquired from an in vitro mock circulatory loop. The entire operating range of the pump was examined, including flows from -2 to 12 L/min. Taking the pump feedback signals of speed and power, together with the HCT level, as input parameters, several flow estimate models were developed via system identification methods. Three autoregressive with exogenous input (ARX) model structures were evaluated: structures I and II used the input parameters directly; structure II incorporated additional terms for HCT; and the third structure employed as input a non-pulsatile flow estimate equation. Optimal model orders were determined, and the associated models yielded minimum mean flow errors of 5.49% and 0.258 L/min for structure II, and 5.77% and 0.270 L/min for structure III, when validated on unseen data. The models developed in this study present a practical method of accurately estimating iRBP flow in a pulsatile environment.Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
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ABSTRACT: Continuous flow ventricular assist devices (VADs) for mechanical circulatory support (MCS) are generally smaller and believed to be more reliable than pulsatile VADs. However, regarding continuous flow, there are concerns about the decreased pulsatility and ventricular unloading. Moreover, pulsatile VADs offer a wider range in control strategies. For this reason, we used a computer model to evaluate whether pulsatile operation of a continuous flow VAD would be more beneficial than the standard constant pump speed. The computer model describes the left and right ventricle with one-fiber heart contraction models, and the systemic, pulmonary, and coronary circulation with lumped parameter hemodynamical models, while the heart rate is regulated with a baroreflex model. With this computer model, both normal and heart failure hemodynamics were simulated. A HeartMate II left ventricular assist device model was connected to this model, and both constant speed and pulsatile support were simulated. Pulsatile support did not solve the decreased pulsatility issue, but it did improve perfusion (cardiac index and coronary flow) and unloading (stroke work and heart rate) compared with constant speed. Also, pulsatile support would be beneficial for developing control strategies, as it offers more options to adjust assist device settings to the patient's needs. Because the mathematical model used in this study can simulate different assist device settings, it can play a valuable role in developing mechanical circulatory support control strategies.Artificial Organs 07/2009; 33(8):593-603. · 2.00 Impact Factor