Physiologic Control Algorithms for Rotary Blood Pumps using Pressure Sensor Input Edward Bullister, Ph.D. Sanford Reich, Ph.D. APEX Medical, Inc. ISRP August 2001

Why Use Pressure Inputs?  Provides physiologic feedback for pump control.  Provides added-value pump diagnostic and monitoring functions.  Increases capability for patient monitoring.  Potentially increases patient quality of life.

How to Implement?  Control Algorithm Development  Design Strategy to Mimic Patients’ Physiologic Control  Control Algorithm Schematic  Control Algorithm Detail  Control Algorithm Results  Added-Value Diagnostic and Monitoring Functions  Patient Monitoring  Hardware Considerations  Summary

Control Algorithm

Level 1: Basic Control Algorithm  Level 1 Control Input: LVDFP - Left Ventricular Diastolic “Filling Pressure”  Level 1 Control Output: Pump Flow Rate  Proportional Integral Control Algorithm d/dt(Flow) = K * (LVDFP - P desired ) K = 0.1 L/min/mmHg  Flow  Pressure   Simple  Robust

Level 1 Results

Level 2: Exercise Control Algorithm  Level 2 Control Inputs:  Arterial Pressure  Pulse Rate Increase (e.g., during exercise)  Level 2 Control Output:  Desired LVDFP  Level 2 Limits:  Max/min LVDFP  Max/min Arterial Pressure

Level 2 Results

Flow Rate Monitor using Pressure  Pressure Calculated from Pump Speed and Pressure Difference  Independent of Motor Current  Includes High Frequency Content Flow (L/min)  Calculated From Pressure Flow meter Measurement  Time (sec)

Hydraulic Power Monitor  Hydraulic Power (HP) into Blood  Pump: HP pump =  P pump * PumpFlow (continuous)  Heart: HP heart ~  P heart * PumpFlow (measured during systole)

Hardware Considerations  Pressure Sensor Technology  Thin-Film Based  MEMS Based  Any Rotary VAD  Pressure Sensor Placement

Component Analysis Computational Fluid Dynamics (CFD)  Example - Inlet Cannula  Establish optimal location for pressure sensor  Calculate pressure coefficient K for nonlinear relationship:  P = K*V 2

Summary  An initial control algorithm has been implemented to auto- regulate rotary blood pumps using physiological pressure inputs.  Two levels of control for a rotary pump have been tested in a mock loop setup.  The pressure signals produce added-value information.  Additional monitoring and control levels have been conceived.  Goal is to contribute to patient quality of life.