Ventricular Assist Device Test Loop Client: Minnetronix, Inc. Advisor: Kristyn Masters Team: Joe Bothwell, Dan Carlson, Kayla Ericson, and David Ugai

Overview Re-cap of project and progress of last semester Experimental Methods Modifications to Design Final Performance Objectives

Ventricular Assist Device (VAD) A VAD is a device used to bridge heart failure patients to a transplant. Minnetronix makes embedded software for VADs. Figure 1: Schematic of a VAD in relation to the patient’s body [1].

VAD Test Loop Client Requirements: Figure 2: Design components of the VAD loop. (1) Harvard Apparatus Pulsatile Pump; (2) needle valves; (3) VAD; (4) flow meters; (5) pressure sensors; (6) compliance chamber; (7) resistance clamp; (8) reservoir.

VAD Test Loop Figure 3: Image of the VAD test loop.

Experimental Design Testing Parameters:  Pressure  Flow Rate  Consistency/Repeatability  Location/orientation of pressure sensors  Specifications of pressure sensors  Calculated loss of pressure through pressure sensor tube

Pressure Sensors Tested pressure clamp Oscilloscope Voltage Output  1V=100mmHg Noise  Increases with stoke rate Labview Figure 4: Output reading from the pressure sensor as seen on the oscilloscope. Stroke rate was set at 40 bpm and with the conversion factor the pressure was 1,500 mm Hg.

Experimental Design Variables Considered : - Consistency of pumping ratio at different stroke rates. - The flow rate of the pump. - The systole/diastole ratio of the pump. Data Acquisition: -Used an oscilloscope to visualize the trace. -Writing an acquisition program in LabView. -Flow rate is calculated as a function of stoke rate and stroke volume (CO=SR*SV).

Experimental Design Pressure Clamp Data Values (with LCD only): RateSVSystole %Diastole %Pressure (mmHg) *

Design Modifications Compliance Chamber - A pressure valve and gauge may be installed to provide more control. - This component has the most variability. Reservoir: - The fluid input was moved to a lower location to simulate a diastolic pressure. - A 1.08 meter column (0.99m for a 74/26 water/glycerine solution) would be needed, or a pressure of ~1.5 psi (pressure=g*h*р).

Performance Objective Requirements: – Design must maintain a selected systolic pressure ranging from mmHg indefinitely. –Must statistically correspond to specific settings. – All settings must be validated using a glycerin solution and a continuous flow pump to simulate a VAD Validation: –An ANOVA test with a significance level of p=.05 and a power of 80%. –Number of trials will be established when we better understand the variance of the pressure values. *settings must be changed between each test

References Images [1] Online, Physicians of St. Louis University, Additional sources Cianci, P, Lonergan-Thomas, H, Slaughter, M, & Silver, M. (2003). Current and Potential Applications of Left Ventricular Assist Devices. Journal of Cardiovascular Nursing, 18;1, Cleveland Clinic Heart Center Online. (2005). Retrieved December 4, 2005 from Copeland, J.G. et al.(2004). Cardiac Replacement with a Total Artificial Heart as a Bridge to Transplantation. The New England Journal of Medicine, 351; 9, Klabunde, R.E (2005). Determinants of Resistance to Flow (Poiseuille’s Equation) Cardiovascular Physiology Concepts Liu, Y. et al. (2005). Design and initial testing of a Mock Human Circulatory Loop for LVAD performance testing. The Journal of Artificial Organs, 29, 4, Maloney, L. (2003, November). Tour de force. Test & Measurement World, McCarthy, P.M. & Smith, W.A.(2002). Mechanical Circulatory Support-a Long and Winding Road. Science: The Bionic Human, 295, Reul, R. & Akdis, M. (2004). Temporary or permanent support and replacement of cardiac function. Future Drugs Online Journal. Retrieved October 2, 2005 from Saint Louis University School of Medicine, Division of Surgery. (2005). Retrieved October 17, 2005 from