Leg Ergometer for Blood Flow Studies

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Leg Ergometer for Blood Flow Studies

• Amy Weaver, Cali Roen,
• Lacey Halfen, Hyungjin Kim
• BME 201
• March 9, 2007

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• Client William Schrage
• Dept. of Kinesiology
• Advisor Paul Thompson
• Dept. of Biological Systems Engineering

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Overview

• Problem statement
• Background
• Design requirements
• Design alternatives
• Proposed Design
• Future work

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Problem Statement

• Test subject will use the ergometer to maintain a
  constant kicking motion
• Leg must passively return to original position
• Femoral artery is imaged using an ultrasound
• Used to determine blood flow to the leg during
  exercise

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Background Blood Flow Research

• Measure blood flow in femoral artery
• Examine how smaller blood vessels regulate
  upstream (femoral) blood flow
• Infuse drugs into the femoral artery

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Background Blood Flow Research

• Two research questions
• What are the neural, metabolic, and vascular
  signals controlling blood flow at rest and
  exercise?
• How do conditions like aging and cardiovascular
  diseases (obesity, high blood pressure, etc)
  alter the regulation of blood flow
• Wider implications
• understanding blood pressure control
• correlated with obesity, diabetics, and high
  blood pressure

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Background Existing Devices

• Current device in use at Mayo Clinic
• Used part of an exercise bike and a car seat
• Boot is a rollerblade boot with the toe cut out
• Device was unreliable, and had variable forces

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(No Transcript)
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Background Existing Devices Cont.
http//www.rehab.research.va.gov/jour/01/38/1/chin
.html
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http//www.hanix.net/en/powermax.htm
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Design Requirements

• Streamlined and compact with minimal loose parts
• Minimum lifespan of five years
• Easily portable (with wheels)
• 5 long x 3 wide
• Chair positioned at various angles from vertical
  and 3 above ground
• Adjust for people of heights 54 to 64
• Flexible range of motion for full leg extension
  while kicking

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Design Requirements

• Passive return to rest position of the leg after
  kicking
• Set up for right leg testing
• Wattage (0-100 W) and kick rate (30-60 KPM)
  output to a laptop through an A/D converter
• Maintain a constant wattage throughout testing
• Adjustable force between tests
• Under 2,000

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Design Alternatives

• Seat for pateint
• Reclining
• Adjustable height
• Boot for foot
• Straps to hold shoe
• Adjustable force
• Wheels for movement
• Sensors
• Wattage
• Kicking rate

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Design Alternatives Gas Spring Shock

• Force from compression of gas in a cylinder
• Function of velocity
• Can be purchased in various sizes with variable
  force
• Use a cable, allowing for full range of kicking
  motion
• Disadvantages
• Springs back to initial position

http//www.globalspec.com/FeaturedProducts/Detail/
IndustrialGasSprings/Stainless_Steel_Gas_Springs_/
34982/0?fromSpotlight1
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Design Alternatives One Way Clutch

• Allows rotation in only one direction
• When clutch locks, friction device is engaged
• When foot is returning, clutch freely rotates
• Clutch attached to boot by a bar with ball joints

http//www.mie.utoronto.ca/staff/projects/cleghorn
/Textbook/DataFiles/Appendix-B/Appendix-B.html
http//adcats.et.byu.edu/WWW/Publication/94-1/Pape
r1-12_6.html
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Design Alternatives with Drum Brake

• Shoes push out against drum providing friction
• Force is constant
• Adjustable by altering force normal to drum
• Disadvantages
• Properties change with heat
• Brake pedals need to be replaced

http//www.howstuffworks.com/drum-brake.htm/printa
ble
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Proposed Design with Viscous Friction

• Viscous friction for force against kick
• Two pieces of metal with liquid between
• Force µAv / t
• Force altered by changing area
• Force remains constant through minor temperature
  changes

http//galileo.phys.virginia.edu/classes/152.mf1i.
spring02/Viscosity.htm
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Design Matrix
Weight Gas Spring Shock One Way Clutch w/ viscous friction One Way Clutch w/ Drum Brake
Overall Reliability 20 0.75 0.9 0.65
Ease to Construct 5 1 0.8 0.8
Maintenance Required 15 0.8 0.8 0.6
Ease of Use 10 0.7 0.7 0.6
Consistent Force 15 0.6 0.8 0.6
Flexible Kicking Motion 10 1 0.8 0.8
Passive Kicking Return 20 0.25 1 1
Force Adjustability 5 1 1 0.7

Total (Out of 100) 68 86 72.5
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Future Work

• Finalize design
• Order components
• Construct design
• Test and modify

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References

• Maximal Perfusion of Skeletal Muscle in Man (Per
  Andersen and Bengt Saltin) 1984
• Professor Fronczak
• ADCATS at Brigham Young University
  http//adcats.et.byu.edu/WWW/Publication/94-1/Pape
  r1-12_6.html