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
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:
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
Ideas we’ve tossed out External control Problems Still have problems with the port Patients could unhook the device if uncomfortable
Ideas we’ve tossed out Syringe pump Dead space behind it No mechanical advantage The ones out there are too large for implantation
Basis of our ideas Car-jack Pacemaker Squeezing on fluid bag gallery/models/thumb/CarJackModel.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
Motor Selected Micromo AM 2224 DC Motor Low Voltage = Low RPM = Max Torque 2 cm diameter 4 cm long Price : $
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 cm
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 Pressure Rauth, Thomas. “Why use Pressure Directed Lap-Band Adjustment?” Vanderbilt Center for Surgical Weight Loss, Nashville, TN. 17 Oct
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 -
Bag to Hold Saline Saline-Filled Bag Exploring several options: 1) Bag Material 2) 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