Rapid MicroInjector for Stiffness Measurement in Mice Hearts

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Rapid Micro-Injector for Stiffness Measurement in
Mice Hearts

• Client Ken Campbell, Ph.D.
• Advisor Glennys Mensing
• Team Mouse Heart
• Michael Kosir
• Ankur Sharma
• Steve Trier

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Overview

• Problem Definition
• Background
• Product Design Specifications
• Preliminary Designs
• Decision Matrix
• Future Considerations

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Problem Definition

• To design a device that can rapidly pump saline
  into a catheter for stiffness measurements during
  specific intervals in the cardiac cycle.
• Inject 3 ?L of saline in less than 5 ms
• Remove injected portion
• Stiffness ?P/?V
• Already a device to measure ?P
• Need a device to cause a ?V

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Background/Motivation

• Diastolic Dysfunction
• Impaired ventricular filling
• Decreased stroke volume from LV
• Greater end-diastolic pressure
• Cause
• Delayed ventricular relaxation and stiffness of
  ventricular walls
• Implicated in more than 70 of heart failure
  patients that are 80

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Pressure/Volume Loops
Ventricle Contracts
End Systole
Aortic Pressure
Filling Pressure
End Diastole
Source Campbell, 2003
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Pressure/Volume Loops
Ventricle Contracts with a smaller volume of blood
End Systole
Aortic Pressure
Increased diastolic chamber stiffness reduces
stroke volume
Filling Pressure
End Diastole
Source Campbell, 2003
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Design Specifications

• Inject a fixed quantity (3-5 µl) of saline
  through a catheter into a left ventricular
  balloon
• Operate in less than 5 ms
• Attach to a catheter with 200 µm diameter opening
• Must operate with an electrical logic pulse
• Length of catheter from fluid injector to end of
  tube is at least 2-3 cm

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Project Overview
Source Campbell, 2003
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Design 1 Solenoid Armature

• FEATURES
• Electromagnet with a coil and movable armature
• When coil is energized, armature moves
• Armature spring-loaded for retraction

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Solenoid Armature

• Advantages
• Inexpensive
• Simple circuitry
• Disadvantages
• Hard to accelerate armature fast enough
• Hard to build on a small scale

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Design 2 Hydraulic Electronic Unit Injector
(HEUI)
Electronic Pulse Control
High Pressure Oil Input
Oil Pump
Fuel Input
Need to adapt nozzle to catheter
Developed by
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Hydraulic Electronic Unit Injector (HEUI)

• Advantages
• Injection pressure control
• Rapid injection rate
• Electronic control of injection
• Compact
• Disadvantages
• High Cost (not HEUI, but Oil Pump)
• Preset volume injection volume (volumes may be
  too high)

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Design 3 Piezoelectric Stack
Source http//www.physikinstrumente.de
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Piezoelectric Stack

• Advantages
• Sub-millisecond response
• Distance proportional to voltage
• Fluid removed
• Disadvantages
• Cost
• Fabrication of piston and nozzle

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Decision Matrix
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Whats Next

• Contacting piezo stack suppliers
• Fabricating piston and nozzle
• Connecting catheter and nozzle
• Operating on logic pulse

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Questions???