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

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 DollarsFinkelstein, Fiebelkorn, and Wang, 2003NHA = National Health AccountsMEPS = Medical Expenditure Panel SurveyBased 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 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

0

.5

1

1.5

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2.5

Vo

lum

e (

mL)

0 1 2 3 4Adjustment Number

Volume Trend Opening VolumeFill Volume

Intra-Band Volume by Adjustment

Fill

Fill

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

0

.5

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Ba

nd

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mL)

0 1 2 3 4Adjustment Number

Intraband Volume Opening VolumeFill Volume

Band Volume by Adjustment

Intra-Band Pressure Degrades between Adjustments

In-Vivo Band

0

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Pre

ssure

(m

mH

g)

0 1 2 3 4Adjustment Number

Pressure Trend Opening PressureFill Pressure

Intra-Band Pressure by Adjustment

Fill

Fill

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

0

100

200

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700

800

Ba

nd

Pre

ssure

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mH

g)

0 1 2 3 4Adjustment Number

Intraband Pressure Opening PressureFill Pressure

Band Pressure by Adjustment

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 nothingGreater th

an Target

Equal

Less than Target

FlexiForceForce Sensors

Versatile, durable piezoresistive force sensor Variety of shapes and sizes Resistance inversely proportional to applied force Customizable Senses contact force

http://www.tekscan.com/flexiforce/flexiforce.html Force vs. Resistance and Force vs. Conductance (1/R)

Pressure versus Band Displacement

Current Band

Volume vs. Diameter

y = -0.2855x + 2.6273

R2 = 0.9798

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Volume (mL)

Dia

me

ter

(cm

)

Band Contraction vs. Contact Pressure

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0 0.5 1 1.5 2 2.5 3 3.5 4

Band Contraction (cm)

Co

nta

ct P

ress

ure

(m

mH

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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