McConahy, Douglas
(2007)
Application of Multiobjective Optimization to Determining an Optimal Left Ventricular Assist Device (LVAD) Pump speed.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
A Left Ventricular Assist Device (LVAD) is a mechanical pump used to assist the weakened left ventricle to pump blood to the entire body. One method of controlling pump speed is using a closed-loop controller that changes the pump speed based on the patient's level of activity and demand for cardiac output. An important aspect of the development of a closed-loop controller is the selection of the desired pump speed. Pump speed must be chosen such that the patient receives adequate cardiac output for his/her level of activity. The pump must also operate in a safe physiological operating region, placing constraints on other hemodynamic parameters. This work presents the pump speed selection problem as a multiobjective optimization problem, considering constraints on cardiac output, left atrial pressure, and arterial pressure. A penalty function is assigned to each hemodynamic variable and a mathematical model of the LVAD and cardiovascular system is used to map the penalty functions as functions of the hemodynamic parameters to penalty functions as functions of pump speed. The penalties for the different variables are combined by forming a weighted sum, and the best set of pump speeds is determined by minimizing the combined penalty functions using different sets of weights. The resulting set of best pump speeds forms the noninferior set (Zadeh, IEEE Trans. On Auto. Control, 1967). It was discovered that the noninferior set contains discontinuities, so the concept of a modified noninferior set known as the Clinician's noninferior set is introduced.A decision support system (DSS) is presented that allows clinicians to determine a single pump speed from the noninferior set by investigating the effects of different speeds on the hemodynamic variables. The DSS is also a tool that can be utilized to help clinicians develop a better understanding of how to assign weights to the different hemodynamic variables.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
25 September 2007 |
| Date Type: |
Completion |
| Defense Date: |
16 May 2007 |
| Approval Date: |
25 September 2007 |
| Submission Date: |
22 May 2007 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Electrical Engineering |
| Degree: |
MSEE - Master of Science in Electrical Engineering |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
left ventricular assist device; LVAD; multiobject optimization; non-inferior set; penalty function; rotary blood pump |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-05222007-142139/, etd-05222007-142139 |
| Date Deposited: |
10 Nov 2011 19:45 |
| Last Modified: |
15 Nov 2016 13:43 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/7933 |
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