FLOW FIELD MEASUREMENT IN THE PENN STATE 12 CC PVAD USING PARTICLE IMAGE VELOCIMETRY (PIV)
Open Access
- Author:
- Wivholm, Brandon David
- Graduate Program:
- Bioengineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Keefe B Manning, Thesis Advisor/Co-Advisor
- Keywords:
- PIV
Pediatric Ventricular Assist Device
PVAD - Abstract:
- Pulsatile cardiac assist pumps have been used with success in adult patients, but scaling down these pumps for the pediatric population has been troublesome. In order to understand the overall flow fields of the 12 cc Penn State pediatric ventricular assist device, particle image velocimetry (PIV) was used. Two dimensional velocity profiles were taken of flow in the center of the chamber. Planes parallel and perpendicular to the diaphragm, which included both the inlet and outlet ports, were collected. These profiles were then examined throughout the cardiac cycle. Regions of low fluid velocities were monitored to see if they persisted for extended periods of time, as these could contribute to clot formation. Comparisons between a Newtonian and Non-Newtonian human blood analog were made, as well as comparisons of varying hematocrit and a goat blood analog. There were significant differences in the flow fields produced in Newtonian and Non-Newtonian blood analogs in this device. These differences were most apparent in the velocity profiles of the inlet and outlet jets, but also lead to differences in the rotational flow that occurs in the device. The effect of hematocrit on the flow through the device was less apparent. The higher hematocrit fluid had more uniform inlet and outlet jets, a sustained major and minor orifice inlet jet and a delayed onset of rotational flow. A comparison of our goat blood analog and our 20% HCT human blood analog showed differences in both the strength and shape of the inlet and outlet jets. The recirculation in the outlet port during systole occurred much later in the cycle when using the goat blood analog. This led to lower velocities in the outlet port during outflow. Our studies showed marked differences in flow profiles compared to our larger VADs. It is important to use a blood analog that accurately mimics human blood in order to get meaningful data. A number of design modifications should be investigated. Either enlarging the outlet valve or placing the outlet valve outside the body of the pump may help reduce flow separation upstream of the valve occluder. Further consideration should be taken regarding valve choice, valve orientation, and systolic duration in order to improve flow performance.