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