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In-vivo Device for Measuring and Adjusting Lap-Band Pressure John Huidekoper Mark Fritz Chris Schroeder Andrew Koivuniemi David Mayhew ©Bill Watterson Advisors: Dr. Robert Roselli Dr. Thomas Rauth
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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
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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 Ref: Research done by Dr. Thomas Rauth
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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
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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
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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
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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
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Torque Considerations
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Current Pump Design
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Motors Stepper motors Provides fine tuning in angular position Good with micro- controller Provides detent torque Prototyping Use a DC motor www.wikipedia.com/
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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/
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Gearing Advantages Increased Torque Increased Precision Disadvantage Occupies Space Less Efficient Tried to make our own Problem- Small Gears are very expensive
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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 cm www.portescap.com/
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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
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Necessity of Pump Control Desired Curve Pressure Adjustment Loss of Pressure Rauth, Thomas. “Why use Pressure Directed Lap-Band Adjustment?” Vanderbilt Center for Surgical Weight Loss, Nashville, TN. 17 Oct. 2006.
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RF Control Chip Negative Feedback Control Pressure Drop in Lap-Band Pressure Transducer Detects Changes Data Processing of Multiple Readings Chip Determines Necessary Volume Pump Changes Volume Of Saline in Lap-Band -
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Bag to Hold Saline Saline-Filled Bag Exploring several options: 1) Bag Material 2) Bag Fabrication Prototype Pump -Easily disassembled -Experiment with bag designs
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Progress Summary Pump Design Pump Fabrication Electronics (Chip, Pressure Transducer, Battery, Motor Control) Bag Design/Fabrication
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