A mock circulatory loop for designing and evaluating total artificial hearts

Love, Holley C.; Timms, Daniel; Nestler, Frank; Frazier, O.H.; Cohn, William E.

doi:10.1109/embc.2014.6944913

Cited by 7 publications

(8 citation statements)

References 13 publications

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“…Pump performance in vitro was evaluated with regard to pulsatile hemodynamic values and electrical power consumption, comparing four simple and two more‐complex custom waveforms over a wide range of pulse amplitudes. A speed profile comparison was performed with the latest iteration of the BiVACOR in a previously developed mock circulatory loop , which was modified for TAH evaluation (Fig. ).…”

Section: Methodsmentioning

confidence: 99%

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

et al. 2016

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Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility.

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Section: Methodsmentioning

confidence: 99%

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

et al. 2016

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“…Also Left Ventricular Assist Devices (LVAD) have been used to generate realistic flow conditions controlled by a pneumatic apparatus. 42 By introducing computer-controlled ventricles in the M-MCL, researchers gained the ability to alter cardiac output which allowed simulation of exercising conditions [43][44][45] and pathological conditions such as congestive left heart failure, 39,[46][47][48][49][50][51] right heart failure, 46 valve regurgitation 52,53 and cardiac arrhythmias. 54 Timms et al 55 used a pneumatic ventricle in an M-MCL to simulate normal and heart failure at rest by adjusting mean arterial pressure, heart rate, contractility, SVR, PVR and arterial compliance.…”

Section: Computer Controlled Driving Systemsmentioning

confidence: 99%

Mock circulatory loops used for testing cardiac assist devices: A review of computational and experimental models

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Papaioannou

et al. 2021

Int J Artif Organs

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Heart failure is a major health risk, and with limited availability of donor organs, there is an increasing need for developing cardiac assist devices (CADs). Mock circulatory loops (MCL) are an important in-vitro test platform for CAD’s performance assessment and optimisation. The MCL is a lumped parameter model constructed out of hydraulic and mechanical components aiming to simulate the native cardiovascular system (CVS) as closely as possible. Further development merged MCLs and numerical circulatory models to improve flexibility and accuracy of the system; commonly known as hybrid MCLs. A total of 128 MCLs were identified in a literature research until 25 September 2020. It was found that the complexity of the MCLs rose over the years, recent MCLs are not only capable of mimicking the healthy and pathological conditions, but also implemented cerebral, renal and coronary circulations and autoregulatory responses. Moreover, the development of anatomical models made flow visualisation studies possible. Mechanical MCLs showed excellent controllability and repeatability, however, often the CVS was overly simplified or lacked autoregulatory responses. In numerical MCLs the CVS is represented with a higher order of lumped parameters compared to mechanical test rigs, however, complex physiological aspects are often simplified. In hybrid MCLs complex physiological aspects are implemented in the hydraulic part of the system, whilst the numerical model represents parts of the CVS that are too difficult to represent by mechanical components per se. This review aims to describe the advances, limitations and future directions of the three types of MCLs.

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“…A so‐called mock circulation (MC) allows the in vitro investigation, development, and testing of VADs. Instead of blood, the majority of mock circulations use an aqueous‐glycerol solution to mimic the viscosity of blood in the human body.…”

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confidence: 99%

“…Figure shows the varying viscosity of the working fluids used in several state‐of‐the‐art MCs that have been published within the last 7 years using an aqueous‐glycerol solution with specified values of mixture ratio or viscosity . When only the mixture ratio was specified, we used Cheng's equation to calculate the viscosity assuming a room temperature of 25°C and a mixture ratio being given in mass percentage.…”

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Control of the Fluid Viscosity in a Mock Circulation

et al. 2017

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A mock circulation allows the in vitro investigation, development, and testing of ventricular assist devices. An aqueous-glycerol solution is commonly used to mimic the viscosity of blood. Due to evaporation and temperature changes, the viscosity of the solution drifts from its initial value and therefore, deviates substantially from the targeted viscosity of blood. Additionally, the solution needs to be exchanged to account for changing viscosities when mimicking different hematocrits. This article presents a method to control the viscosity in a mock circulation. This method makes use of the relationship between temperature and viscosity of aqueous-glycerol solutions and employs the automatic control of the viscosity of the fluid. To that end, an existing mock circulation was extended with an industrial viscometer, temperature probes, and a heating nozzle band. The results obtained with different fluid viscosities show that a viscosity controller is vital for repeatable experimental conditions on mock circulations. With a mixture ratio of 49 mass percent of aqueousglycerol solution, the controller can mimic a viscosity range corresponding to a hematocrit between 29 and 42% in a temperature range of 30-428C. The control response has no overshoot and the settling time is 8.4 min for a viscosity step of 0.3 cP, equivalent to a hematocrit step of 3.6%. Two rotary blood pumps that are in clinical use are tested at different viscosities. At a flow rate of 5 L/min, both show a deviation of roughly 15 and 10% in motor current for high rotor speeds. The influence of different viscosities on the measured head pressure is negligible. Viscosity control for a mock circulation thus plays an important role for assessing the required motor current of ventricular assist devices. For the investigation of the power consumption of rotary blood pumps and the development of flow estimators where the motor current is a model input, an integrated viscosity controller is a valuable contribution to an accurate testing environment. Key Words: Ventricular assist device-Blood pump-Viscosity controller-Flow estimator-Flow probe calibration.Despite significant clinical and technical developments, heart failure remains one of the major health challenges in developed countries (1). For end-stage heart failure, the only option next to heart transplantation is the implantation of a ventricular assist device (VAD). A so-called mock circulation (MC) allows the in vitro investigation, development, and testing of VADs. Instead of blood, the majority of mock circulations (2-11) use an aqueous-glycerol solution to mimic the viscosity of blood in the human body.The viscosity of human blood mainly depends on the hematocrit (12), whereas the viscosity of an aqueous-glycerol solution depends on its mixture ratio and temperature. In this study, viscosity is defined as the dynamic viscosity that yields a measure of internal resistance to flow. Viscosity has the unit centipoise (cP) which is equal to millipascalsecond (mPaÁs). The viscosity of bloo...

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A mock circulatory loop for designing and evaluating total artificial hearts

Cited by 7 publications

References 13 publications

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller

Mock circulatory loops used for testing cardiac assist devices: A review of computational and experimental models

Control of the Fluid Viscosity in a Mock Circulation

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