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