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

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

Current Lap Band

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

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

Cost of Obesity versus the Current Procedure ITEMSEstimated 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

Problem Statement Currently band loses effectiveness between injections Invasive for the patient Currently 7-14% of soft tissue infection, port leakage and tube cracks

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 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 < , * p < , + p < 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 Frequent self-adjustments will remove the need for 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, port leakage and tube cracks

Factors Biocompatible materials Fabrication Power Limitations – daily/weekly adjustments Cost effectiveness relative to current procedure Less cost involved in device maintenance Failsafe mechanism to avoid severe physical damage

Constriction Control Measure force exerted on band Loosen Tighten Do nothing Greater than Target Equal Less than Target

FlexiForce Force Sensors Versatile, durable piezoresistive force sensor Variety of shapes and sizes Resistance inversely proportional to applied force Customizable Senses contact force Force vs. Resistance and Force vs. Conductance (1/R)

Pressure versus Band Displacement Current Band

Pressure versus Band Displacement Our Band

Short-term Goals Continue Research and design Mechanical design Feedback system (electrical design) Motors Finalize Sketch Begin CAD design Confirm force sensor selection