Browsing by Subject "Cardiovascular system"

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Brushless DC motor modeling and optimal control: a cardiovascular application
(2016-08) Rapp, Ethan Stewart; Longoria, Raul G.; Chen, Dongmei
The increasing use of Ventricular Assist Devices (VADs) in patients with weak or failing hearts has driven a need for more thorough analysis of VAD design, control methods, and cardiovascular dynamic effects. In recent years, studies have shown the potential of applying formal optimization methods to VAD actuation in order to reduce power consumption or improve pump output. This thesis continues the use of formal optimization methods as well as digital analysis using the brushless DC (BLDC) motors within the TORVAD(TM), designed by Windmill Cardiovascular Systems, Inc. (WCS), as a basis. To begin the optimization, a parameterized model of the BLDC motor system has been developed and combined with a lumped parameter model of the cardiovascular system. The combined system is then digitally analyzed under varying rates of TORVAD(TM) motor controller frequencies to determine the minimum frequency at which the system will remain stable and minimize detrimental physiological effects. Formal optimization methods are then introduced and implemented on the combined motor and cardiovascular system model. The output of the optimization is a reference trajectory that minimizes average motor power consumption. This trajectory, along with the results from the digital analysis, provides a more robust examination on the combined motor and cardiovascular system.
Recursive estimation of Systemic Vascular Resistance using measurements from a left ventricular assist device
(2019-05) Pawar, Suraj Rajendra; Longoria, Raul G.
Cardiovascular disease is the leading cause of deaths worldwide, and one of the ways to treat patients with congestive heart failure is to perform a heart transplant. As the demand for this procedure rises, the disproportionate availability of suitable donors needs to be countered with ways to care and sustain patients who are waiting for a transplant. In this regard, the use of left ventricular assist devices (LVAD) has increased. The research conducted in this Thesis is primarily concerned with the TORVAD [superscript TM] (Windmill Cardiovascular Systems In., Austin , TX), a rotary blood pump type LVAD. The load faced by the left ventricle during ejection of blood is termed as Systemic Vascular Resistance (SVR), and is an important parameter that can indicate cardiovascular health. Abnormalities in SVR have been found to be a good indicator of hypertension, heart failure, shock and sepsis. A consistently low SVR can even be a predictor of mortality. The goal of this Thesis is to investigate ways of recursively estimating SVR in a patient, by using measurements that the TORVAD [superscript TM] provides. The Extended Kalman Filter is used to develop an estimation algorithm based on a reduced order model of the cardiovascular system. The estimation accuracy of the algorithm is tested by generating data through simulations of a computational model of the cardiovascular system, and by collecting measurements from the TORVAD [superscript TM] while it operates in a mock circulation loop. The algorithm is found to estimate SVR satisfactorily using the available measurements, and is robust to different initial conditions.