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In-vivo Device for Measuring and Adjusting Lap-Band Pressure
John HuidekoperMark FritzChris SchroederAndrew KoivuniemiDavid Mayhew
©Bill Watterson
Advisors:Dr. Robert RoselliDr. Thomas Rauth
Background Information
Obesity in United States Obese
30 pounds overweight Morbidly obese
100 pounds overweight Or BMI over 40 Effects 9 million Americans
BMI Body Mass Index (Weight*703)/(height^2)
Sources of help Gastric Bypass Lap-Band
Source:http://www.sptimes.com/2003/10/14/Worldandnation/Number_of__extremely_.shtml
Reasons for Design Choices
Problems Device Failure
Leaks (Maude Database) Patient Pain
No Constant Pressure Fixes
Implantable Pump Autonomous Control as
well as Non-Invasive Control
0
100
200
300
400
500
600
Me
an B
and
Pre
ssur
e (
mm
Hg
)
0 1 2 3 4Adjustment Number
press Opening PressureFinal Pressure
Pressure Degradation between Adjustments
Ref: Research done by Dr. Thomas Rauth
Ideas we’ve tossed out
External control Problems Still have problems
with the port Patients could
unhook the device if uncomfortable
http://www.minimed.com/images/x22_features_callout.jpg
Ideas we’ve tossed out
Syringe pump Dead space behind it No mechanical
advantage The ones out there are
too large for implantation
http://www.klf-insurance.com/images_for_site/syringe.jpg
Basis of our ideas
Car-jack Pacemaker Squeezing on fluid
bag
http://www.syncope.co.uk/images/Pacemaker.JPG
http://www.3dkingdom.org/modules/My_eGallery/gallery/models/thumb/CarJackModel.jpg
http://www.uthscsa.edu/mw/photogallery/Media/biomed/images/IV_BAG.jpg
Current Pump Design
Design Parameters Fluid pressure
Max at 2 atm
Screw Torque Max at 4 Nm
Considerations Bi-directional adjustment Space-saving design Torque profile
Torque Considerations
Current Pump Design
Motors
Stepper motors Provides fine tuning
in angular position Good with micro-
controller Provides detent
torque Prototyping
Use a DC motor
www.wikipedia.com/
Motor Selected
Micromo AM 2224 DC Motor Low Voltage = Low
RPM = Max Torque
2 cm diameter 4 cm long Price : $185.88
www.portescap.com/
Gearing
Advantages Increased Torque Increased Precision
Disadvantage Occupies Space Less Efficient
Tried to make our own
Problem- Small Gears are very expensive
Our Gears
Gearhead Attaches to the front
of the motor Increases the torque
several orders of magnitude (1000:1)
4.5 NM torque Does increase motor
length to 7 cmwww.portescap.com/
Safety
Used Design Safe Software Filled out the possible problems and
solutions Conclusions
Most important to have a durable casing Have a long battery life Situate device far from vital organs Provide fail safe if program fail
Necessity of Pump Control
Desired Curve
Pressure Adjustment
Loss of PressureRauth, Thomas. “Why use Pressure Directed Lap-Band Adjustment?” Vanderbilt Center for Surgical Weight Loss, Nashville, TN. 17 Oct. 2006.
RF Control ChipNegative Feedback Control
Pressure Drop in Lap-Band
Pressure TransducerDetects Changes
Data Processing of Multiple Readings
Chip Determines Necessary Volume
Pump Changes VolumeOf Saline in Lap-Band
-
Bag to Hold Saline
Saline-Filled Bag
Exploring several options:1) Bag Material2) Bag Fabrication
Prototype Pump-Easily disassembled-Experiment with bag designs
Progress Summary
Pump Design Pump Fabrication Electronics (Chip, Pressure
Transducer, Battery, Motor Control) Bag Design/Fabrication