ECE 640: Intro to Biomedical Engineering

-Guruprasad A. Giridharan

Human Circulatory SystemThe HeartNatural Control

NervousHumoralLocal

Failing HeartWhy it happens?Effects

Why Model?Learning toolInexpensive research toolFirst step of device designPredict effects and deepen

understandingPlay GOD !! (idealizations,

assumption, know true values)

Modeling:Human Circulatory System

Utah Circulation Model (UCM)

Modeling AssumptionsPhysical parameters are linear and

lumpableBlood flow is influenced only by

pressure, resistance and complianceBlood is a Newtonian fluidIdeal valvesResistance and compliance remains

constant for any block (except heart)

Modeling: Active and Passive blocks

P= Pressure, V= Volume, C= Compliance, F= Flow rate,R=Resistance

Modeling:Human Circulatory System

Modeling:Valves

Modeling:Failing LH, during rest

Modeling:Failing LH, during exercise

Ventricular Assist DeviceWhat is a VAD

Axial & Centrifugal Flow VADsHow does it help?

VAD ControlObjectives

Adequate perfusionAvoiding SuctionLow rpm oscillationsSensor Issues

Previous strategies

©2000 MicroMed Technology, Inc

©2000 MicroMed Technology, Inc

The DeBakey/NASA VAD

VAD Model Equations & Assumptions

RPMTorqueFlow

Modeling:Ventricular Assist Device

Modeling:Ventricular Assist Device

J= Inertia of the rotor, Te= Motor Torque, Tp= Load Torque,= rpm, I= Amplitude of phase current, Fp= Pump Flow rate

Modeling:Model Integration

Modeling: Axial Flow VADModel Integration

Modeling:Model Integration

Modeling:Model Integration

ControlControl Objective

RPM constraint Why P setpoint ? Equations

PI VAD controllerSimulation Results

Control:Constraints and Objective function

Control:Control Schematic with 3 sensors

VAD Control:Weak LH, Centrifugal VAD, at rest

No VAD:Weak LH, during rest

Performance of the PI VAD Controller

Sensor IssuesRequired 3 sensors (2 pressure, 1

rpm)Pressure sensors unreliableData NoiseEstimate pressure using rpm and

currentExtended Kalman filter for estimation

1 Sensor (rpm sensor only)Weak LH with VAD, during rest

1 Sensor (rpm sensor only)Weak LH with VAD, during rest

Performance of the PI VAD Controller with P Estimator

Artificial Vasculature Device (AVD)Conceptual recovery directed device.No damage to the left ventricle.Ability to alter the impedence seen

by the LV.Increase coronary perfusion by

counter-pulsation.

Design and In-vivo setup

Artificial VasculatureConcept Device

Outflow Cannula

Inflow Cannula

Transonic Inflow Probe

LV Pressure/VolumeCatheter

Transonic Outflow Probe

Transonic Coronary ArteryFlow Probe

IntramyocardialPressure Transducer

EmptyingInletValve

Outlet Valve Return

to Aorta

Linear Actuator

Artificial VasculatureConcept Device

To Power Supplyand Controller

FillingInletValve

Outlet Valve

From Aorta

Artificial Vasculature Device (AVD)

S.V

ArtificialValve

AorticValve

e

Left Heart

AVD

Aorta

FS

PS

Rref

FilterRact

FlowSensor

PressureSensorP

S

FS

Controller

Modeling of the AVD

Reduce resistance and increase cardiac output

Reducing Resistance

Controller action