Physiologic Control Algorithms for Rotary Blood Pumps using Pressure Sensor Input
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Transcript of Physiologic Control Algorithms for Rotary Blood Pumps using Pressure Sensor Input
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Physiologic Control Algorithms for Rotary Blood Pumps using Pressure
Sensor Input
Edward Bullister, Ph.D.
Sanford Reich, Ph.D.
APEX Medical, Inc.ISRP 2001
18 August 2001
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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.
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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
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Control Algorithm
Level 1
Average
Integral SpeedController
APS-VADLVDFPInletPressure
+
max
LimitControl
OutletPressure
min
Average ArterialPressure Limits
max
min
--
Level 3
Ventricular Collapse
Detection Algorithm
Retrograde Flow
Detection Algorithm
Level 2 (Exercise)
DP RPM
HR
Limits for Average
Arterial Pressure
LVDFP = Left Ventricular DiastolicFilling Pressure
Desired
APS-VAD CONTROL SCHEME
DP = Differential APS-VAD pressureHR = Heart Rate
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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 - Pdesired)
K = 0.1 L/min/mmHg
Flow Pressure Simple Robust
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Level 1 Results
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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
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Level 2 Results
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Flow Rate Monitor using Pressure
Pressure Calculated from Pump Speed and Pressure Difference
Independent of Motor Current
Includes High Frequency Content F
low
(L
/min
)Calculated From Pressure
Flow meterMeasurement
Time (sec)
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Hydraulic Power Monitor
Hydraulic Power (HP) into Blood Pump: HPpump = Ppump * PumpFlow (continuous) Heart: HPheart ~ Pheart * PumpFlow (measured during systole)
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Hardware Considerations
Pressure Sensor Technology Thin-Film Based MEMS Based
Any Rotary VAD Pressure Sensor Placement
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Component Analysis
Computational Fluid Dynamics (CFD) Example - Inlet Cannula Establish optimal location for pressure sensor
Calculate pressure coefficient K for nonlinear relationship: P = K*V2
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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.