Self-Adjusting Gastric Banding System Erin Crosby Andrew Dickerman Joshua Mabasa Brian Reis

Overview of Gastric Banding Minimally invasive bariatric weight loss procedure for adults with BMI > 35 Involves inflatable gastric band around upper part of stomach Saline solution used to inflate band to decrease appetite

Current Lap Band http://www.lapbandtalk.com/f73/technical-lap-band-reference-15216/

Lap Band Functionality Band reduces stomach size On average: From 1500 mL without band to 30 mL with band in place Induces an early feeling of satiety Feel full quickly after eating small amount Fullness lasts for several hours http://www.elyzea.co.uk/gastric/patient.html

Adjustments with Current Band First adjustment typically done 6 to 8 weeks after surgery Total number of adjustments depends on individual’s weight-loss rate and results Adjustments are simple office visits that only take 10 or 15 minutes

Obesity – Health Care Costs **Expenditure in Billions of Dollars Finkelstein, Fiebelkorn, and Wang, 2003 NHA = National Health Accounts MEPS = Medical Expenditure Panel Survey Based on obesity data from NHIS 1996-7

Cost of Obesity versus the Current Procedure ITEMS Estimated Annual Costs Mean medical/drug costs (BMI≥35) $7,337 Out-of-pocket healthcare expenses $2,684 Employment inactivity costs $1,017 Commercial weight-loss program fees $678 Prescription co-pays (5 meds at $10) $738 Grocery and dining cost $6,012 TOTAL $18,466 Cost of current Lap-Band Procedure (facility, surgeon, and anesthesiologists) can run from $12,000 to $25,000

Success Rate of Current Procedure Average loss of 50% of excess weight in 1-2 years Mortality rate 0.1% Re-operation rate of less than 5% Weight Loss http://www.obesitylapbandsurgery.com/statmain.html

Problem Statement Invasive for the patient Currently 7-14% patients experience soft tissue infection, port leakage and tube cracks Currently band loses effectiveness between injections *add pressure graph in!! * There is incremental pressure loss between band adjustments absent “measurable” loss in band volume

Possible Causes for Pressure Loss Loss of Volume across the semi-permeable silicone membrane that cannot currently be detected Evacuation of trapped air across membrane Reduction of post-operative stomach tissue swelling

Intra-Band Volume is Constant Between Adjustments In-Vivo Band Fill # * + Paired T-test: # p = 0.08 , * p = 0.09, + p = 0.83 From “Pressure Directed Lap-Band Adjustment – Is There a Role?” by Thomas P. Rauth, M.D., Michael D. Holzman, M.D., MPH

Intra-Band Volume is Constant Between Adjustments Ex-Vivo Band From “Pressure Directed Lap-Band Adjustment – Is There a Role?” by Thomas P. Rauth, M.D., Michael D. Holzman, M.D., MPH

Intra-Band Pressure Degrades between Adjustments In-Vivo Band Fill # * + Paired T-test: # p < 0.0001 , * p < 0.0001, + p < 0.0001 From “Pressure Directed Lap-Band Adjustment – Is There a Role?” by Thomas P. Rauth, M.D., Michael D. Holzman, M.D., MPH

Intra-Band Pressure Degrades between Adjustments Ex-Vivo Band From “Pressure Directed Lap-Band Adjustment – Is There a Role?” by Thomas P. Rauth, M.D., Michael D. Holzman, M.D., MPH

Solution Mechanically-constricting, self-adjusting band Will resolve problems associated with fluid-filled system Soft tissue infection around port Port leakage Tube cracks Frequent self-adjustments will reduce number of regular post-op corrections

Primary Objectives Eliminate the need for saline injections and reservoirs used in current systems Automatically maintain a constant applied force in between checkups

Goals Band needs to uniformly constrict stomach through electro-mechanical means Band, motor, pressure sensor, and electronic components all confined to one unit Decrease internal space needed for device Eliminate soft tissue infection around port, port leakage and tube cracks

Design Considerations Fabrication feasibility Battery power limitations – daily/weekly adjustments Cost effectiveness relative to current procedure Less cost involved in device maintenance Factors parameters varied to yield benefit what affects cost, quality, benefits, etc  List them.

Pro/Engineer Model

Pro/Engineer Model

Pro/Engineer Model

Pro/Engineer Model

Pro/Engineer Model ~2 cm

Gearing/Torque Equations Energy Balance Fl => Δr P increases Fl = Prw Force required to maintain constant radius (r) V = Volume c = Circumference w = Width P Δr Fl

Gearing/Torque Equations Fl = Prw Force required to maintain constant radius τr = Torque from motor

FlexiForce Force Sensors Variable resistor Resistance inversely proportional to applied force Versatile, durable piezoresistive force sensor Customizable Senses contact force http://www.tekscan.com/flexiforce/flexiforce.html Force vs. Resistance and Force vs. Conductance (1/R)

Short-term Goals Fabricate prototype Order parts Circuit Design Force sensors Motor Gearhead Circuit Design Testing