A variable gain physiological controller for a rotary left ventricular assist device.

This paper deals with designing a physiological adaptive control law for a turbodynamic ventricular assist device (TVAD) using a lumped parameter time-varying model that describes the cardiovascular system. The TVAD is a rotary blood pump driven by an electrical motor. The system simulation also includes the adaptive feedback controller, which provides a physiologically correct cardiac output under different preload and afterload conditions. The cardiac output is estimated at each heartbeat, and the control objective is achieved by dynamically changing the motor speed controller's reference based on the systolic pressure error. TVADs provide support for blood circulation in patients with heart failure. To improve the performance of these devices, several control strategies have been developed over the years, with an emphasis on the physiological strategies that adapt their parameters to improve the patient's condition. In this paper, a new strategy is proposed using a variable gain physiological controller to keep the cardiac output in a reference value under changes in both preload and afterload. Computational models are used to evaluate the performance of this control technique, which has shown better results of adaptability than constant speed controllers and constant gain controllers.

Simulating cardiac disorders with a lumped parameter synergistic model.

A lumped parameter synergistic model of the human cardiovascular system (CVS) is proposed to integrate the heart's electrical activity with its mechanical activity. This model can represent the physiological condition of a patient in an effective way, whether it is considered normal or with some cardiac disorders. The electrical activity is coupled to the CVS model through electrocardiogram (ECG) signals in the suggested model. The variations in ECG morphology are detected by appropriate algorithms and changes parameters of the CVS model, such as systemic resistance and end-systolic pressure-volume relationship.Clinical relevance- It provides interpretation and analysis of physiological data of the cardiovascular system, both of electrical and mechanical cardiac behavior, evaluated together.

An Inverse Problem Approach for Parameter Estimation of Cardiovascular System Models.

Left ventricular assist devices (LVADs) are mechanical pumps that help patients with chronic heart failure waiting for a heart transplant. Mathematical models of these devices can be used along cardiovascular system (CVS) models to evaluate the assistance performance under different operating modes. The estimation of the CVS model parameters for a particular patient and numerical simulations allow the implementation of adequate LVAD operation mode. This work presents a method to estimate the parameters of a CVS model using only one hemodynamic variable: the systemic arterial pressure (Ps). Synthetic signals of Ps are used to solve this ill-posed inverse problem partially, and the results show the high accuracy of the proposed method, which achieves 0.5%.Clinical relevance- The measurements of hemodynamic variables using noninvasive techniques avoid many clinical problems arising from invasive measures such as infections.