Invivo Device for Measuring and Adjusting LapBand Pressure
In-vivo Device for Measuring and Adjusting Lap-Band Pressure ©Bill Watterson John Huidekoper Mark Fritz Chris Schroeder Andrew Koivuniemi David Mayhew Advisors: Dr. Robert Roselli Dr. Thomas Rauth
Background Information n Obesity in United States ¡ Obese n ¡ Morbidly obese n n n ¡ 100 pounds overweight Or BMI over 40 Effects 9 million Americans BMI n n n 30 pounds overweight 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 n Problems ¡ Device Failure n n ¡ n 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
Ideas we’ve tossed out n External control Problems ¡ ¡ Still have problems with the port Patients could unhook the device if uncomfortable http: //www. minimed. com/images/x 22_features_callout. jpg
Ideas we’ve tossed out n Syringe pump ¡ ¡ ¡ http: //www. klf-insurance. com/images_for_site/syringe. jpg Dead space behind it No mechanical advantage The ones out there are too large for implantation
Basis of our ideas n n n Car-jack Pacemaker Squeezing on fluid bag http: //www. syncope. co. uk/images/Pacemaker. JPG http: //www. 3 dkingdom. org/modules/My_e. Gallery/ gallery/models/thumb/Car. Jack. Model. jpg http: //www. uthscsa. edu/mw/photogallery/Media/biomed/images/IV_BAG. jpg
Current Pump Design n Design Parameters ¡ Fluid pressure n ¡ Screw Torque n n Max at 2 atm Max at 4 Nm Considerations ¡ ¡ ¡ Bi-directional adjustment Space-saving design Torque profile
Torque Considerations
Current Pump Design
Motors n Stepper motors ¡ ¡ ¡ n Provides fine tuning in angular position Good with microcontroller Provides detent torque Prototyping ¡ Use a DC motor www. wikipedia. com/
Motor Selected n n n Micromo AM 2224 DC Motor Low Voltage = Low RPM = Max Torque 2 cm diameter 4 cm long Price : $185. 88 www. portescap. com/
Gearing n Advantages ¡ ¡ n Disadvantage ¡ ¡ n n Increased Torque Increased Precision Occupies Space Less Efficient Tried to make our own Problem- Small Gears are very expensive
Our Gears n 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/
Safety n n n 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 Pressure Adjustment Desired Curve Loss of Pressure Rauth, Thomas. “Why use Pressure Directed Lap-Band Adjustment? ” Vanderbilt Center for Surgical Weight Loss, Nashville, TN. 17 Oct. 2006.
RF Control Chip Negative Feedback Control - Pressure Drop in Lap-Band Pressure Transducer Detects Changes Pump Changes Volume Of Saline in Lap-Band Data Processing of Multiple Readings Chip Determines Necessary Volume
Bag to Hold Saline Exploring several options: 1) Bag Material 2) Bag Fabrication Saline-Filled Bag Prototype Pump -Easily disassembled -Experiment with bag designs
Progress Summary n n Pump Design Pump Fabrication Electronics (Chip, Pressure Transducer, Battery, Motor Control) Bag Design/Fabrication
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