Numerical Optimization Studies of Cardiovascular–Rotary Blood Pump Interaction

Lim, Einly; Dokos, Socrates; Salamonsen, Robert F.; Rosenfeldt, Franklin; Ayre, Peter J.; Lovell, Nigel H.

doi:10.1111/j.1525-1594.2012.01449.x

Cited by 29 publications

(34 citation statements)

References 21 publications

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“…The speed of the centrifugal pump was controlled by a proportional integral controller with a time constant of about 3.5 ms [26]. The IRBP includes an impeller with four blades [27].…”

Section: A Signal Acquisitionmentioning

confidence: 99%

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Classification of Implantable Rotary Blood Pump States With Class Noise

Ooi

Seera

et al. 2016

IEEE J. Biomed. Health Inform.

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A medical case study related to implantable rotary blood pumps is examined. Five classifiers and two ensemble classifiers are applied to process the signals collected from the pumps for the identification of the aortic valve nonopening pump state. In addition to the noise-free datasets, up to 40% class noise has been added to the signals to evaluate the classification performance when mislabeling is present in the classifier training set. In order to ensure a reliable diagnostic model for the identification of the pump states, classifications performed with and without class noise are evaluated. The multilayer perceptron emerged as the best performing classifier for pump state detection due to its high accuracy as well as robustness against class noise.

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“…The speed of the centrifugal pump was controlled by a proportional integral controller with a time constant of about 3.5 ms [26]. The IRBP includes an impeller with four blades [27].…”

Section: A Signal Acquisitionmentioning

confidence: 99%

“…The experiment was first implemented with a speed ramp under healthy conditions, from a pump speed of 1600 rpm to 3000 rpm, at an increment of 100 rpm [26]. This was then followed by different perturbations to vary cardiac contractility, afterload and preload.…”

Section: A Signal Acquisitionmentioning

confidence: 99%

Classification of Implantable Rotary Blood Pump States With Class Noise

Ooi

Seera

et al. 2016

IEEE J. Biomed. Health Inform.

Self Cite

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“…Suction events were simulated in the same manner as Lim [139], who defined the resistance between LV and pump inlet as a variable resistance Rsuc. Under normal operation, Rsuc is set to zero.…”

Section: Variable Rangementioning

confidence: 99%

“…Klein Ohio, Plain City, OH) installed between the ventricles and VAD inlet ports. These valves were used to set the inflow cannula resistance as a function of ventricular volume, adapting the relationship used by Lim [139]. This relationship is described by Equation (3.6).…”

Section: Variable Rangementioning

confidence: 99%

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Automatic control of dual left ventricular assist devices as a biventricular assist device

Stevens¹

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In this thesis, we investigate automated methods for the control of rotary blood pumps in the treatment of heart failure. Heart failure is a common end-point for many forms of cardiovascular disease resulting in significant morbidity and mortality. Ventricular assist devices (VADs) are blood pumps designed to assist a failing heart and are used both to support patients whilst they are awaiting a heart transplant, or as an alternative to transplantation. Small rotary VADs can provide long-term support of the left ventricle (LVAD), right ventricle (RVAD) or both ventricles of the heart simultaneously.Unfortunately, the lack of a commercially available rotary RVAD has led to the implantation of two rotary LVADs as an ad hoc biventricular assist device (BiVAD). Clinicians currently operate such dual LVADs at a constant speed, which ensures balanced left and right pump flows for inactive patients.However, changes in levels of patient activity will lead to altered cardiac output requirements, which may disturb this balance. In turn, this can lead to undesirable events such as pulmonary venous congestion or ventricular suction. A control system that automatically adjusts pump speed with changes in the required cardiac output could alleviate such events and so offer significant benefits. However, while such physiological control systems have been investigated for single LVADs, limited work has been completed on dual LVAD control. In addition, there is no generally accepted framework for the evaluation of these systems that encompasses a broad range of patient scenarios, activity levels and heart conditions. Therefore, the primary aim of this thesis was to develop and evaluate a number of physiological control systems suitable for dual rotary LVADs.The first objective was to characterise the methods that are currently used to operate dual LVADs in the clinic. Using both in-vitro and in-vivo methods, it was shown that balanced left and right flow rates could be obtained by operating the RVAD slower than the LVAD, albeit at speeds below the manufacturer's recommendations (1400 -1800 RPM), which, according to other investigators, may adversely affect impeller washout. Operating both at the same design speed is only possible in patients with high pulmonary vascular resistance (PVR), high left ventricular contractility or high RVAD outflow cannula resistance. This thesis demonstrates that if the RVAD outflow cannula is restricted to a diameter between 6.5 and 8.1 mm, suitable steady-state haemodynamics (systemic flow rate 5 L.min -1 , MAP 90mmHg and LAP less than 25mmHg) can be achieved while maintaining impeller stability and optimal device washout. It was also established that changes in pump speed or outflow graft diameter were required to overcome elevations in pulmonary vascular resistance, thereby justifying the necessity of a physiological control system for dual LVADs.The second objective was to develop an in vitro evaluation protocol for control system testing utilising a mock circulation loop (MCL). The test...

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Numerical Simulation of a Biventricular Assist Device with Fixed Right Outflow Cannula Banding During Pulmonary Hypertension

Nadeem

Lim

et al. 2015

Ann Biomed Eng

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As a left ventricular assist device is designed to pump against the systemic vascular resistance (SVR), pulmonary congestion may occur when using such device for right ventricular support. The present study evaluates the efficacy of using a fixed right outflow banding in patients receiving biventricular assist device support under various circulatory conditions, including variations in the SVR, pulmonary vascular resistance (PVR), total blood volume (BV), as well as ventricular contractility. Effect of speed variation on the hemodynamics was also evaluated at varying degrees of PVR. Pulmonary congestion was observed at high SVR and BV. A reduction in right ventricular assist device (RVAD) speed was required to restore pulmonary pressures. Meanwhile, at a high PVR, the risk of ventricular suction was prevalent during systemic hypotension due to low SVR and BV. This could be compensated by increasing RVAD speed. Isolated right heart recovery may aggravate pulmonary congestion, as the failing left ventricle cannot accommodate the resultant increase in the right-sided flow. Compared to partial assistance, the sensitivity of the hemodynamics to changes in VAD speed increased during full assistance. In conclusion, our results demonstrated that the introduction of a banding graft with a 5 mm diameter guaranteed sufficient reserve of the pump speed spectrum for the regulation of acceptable hemodynamics over different clinical scenarios, except under critical conditions where drug administration or volume management is required.

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Numerical Optimization Studies of Cardiovascular–Rotary Blood Pump Interaction

Cited by 29 publications

References 21 publications

Classification of Implantable Rotary Blood Pump States With Class Noise

Classification of Implantable Rotary Blood Pump States With Class Noise

Automatic control of dual left ventricular assist devices as a biventricular assist device

Numerical Simulation of a Biventricular Assist Device with Fixed Right Outflow Cannula Banding During Pulmonary Hypertension

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