OXYGEN CONCENTRATOR FILTER RE-DESIGN & TESTING Michael Madea

Biomedical Engineering

Wyatt Albert

Eleventh Annual School of Science, Engineering, and Health Symposium May 2, 2014

CLIENT f Macha Mission Hospital f Dr. John Spurrier f Mr. Melvin Mabeta

f DeVilbiss Healthcare- partnering organization

OXYGEN CONCENTRATORS f Purpose: Delivering

concentrated oxygen for patients f Elderly with respiratory issues f Infants and children with

bronchiolitis

PROJECT IDENTIFICATION f Problem: Premature concentrator failure

f Average life is 43% lower than expected f Non-ideal conditions- humidity and dust f Irregular maintenance f Goal: To sustain oxygen concentrator function

f Increase longevity of machine f Maintain adequate oxygen output f Simplify maintenance procedures

WHAT ARE OXYGEN CONCENTRATORS? f Oxygen concentrators vs. oxygen tanks f Access

f Sieve beds-filter out Nitrogen f Mode of failure

21% Oxygen 78% Nitrogen 1% Other gases

95% Oxygen 5% Other gases

HOW IT WORKS To the Patient Natural Air Depressurizes

Oxygen Gas Nitrogen Purge Pressurizes

Photo: Devilbiss Healthcare

WHAT IS ZEOLITE? f Zeolite f Separates gasses

f Crystal structure f Cage-like resemblance f Molecular exclusion Photo: molecularsive.org

WHY IS PRESSURE IMPORTANT? f Adsorption vs. Absorption

f

Absorption = Chemical Bond (strong)

f Pressure Swing Adsorption f

High pressure = High adsorption

f

Low pressure = Low adsorption

High Temperature

Increasing

Adsorption = Physical bond (weak)

Adsorption

f

Low Temperature

FIRST SOLUTION f Desiccant based filter f Removes humidity f Preserves zeolite functionality f Chose Silica Gel as desiccant

PAST WORK f Designed Dehumidifying Filter f Desiccant based

f Site team trip May 2013 f Evaluated prototype on site f Provided aid with repairs

George Mono and Steven Bandstra 2013

RESEARCH f Desiccant vs. Membrane f Desiccant f Cost effective f Effective over short time f Requires periodic maintenance f Regenerative

f Membrane f No maintenance required f Long lifespan f Expensive - $150/ft2 f Requires dry air source

NAFION MEMBRANE f Tetrafluroethylene – AKA Teflon f Bonded with Sulfonic Acids

f Transports water across f Acid Groups form channels

f Blocks all non polar molecules f O2, N2, ect.

f Passive transport f Requires difference in water

concentration

Credit: Eric Listor

MEMBRANE FILTER

Membrane

HOUSING DESIGN f Decided on a design based on

cost, durability and manufacturability f 3D printed f Extruded ABS plastic

f 2 Halves sealed with rubber

gasket

Photo: Makerbot.com

HOUSING MANUFACTURING

TESTING OF DESIGN f Questions to answer f Will design reduce humidity? f How much membrane material

is needed?

TESTING APPARATUS Humidity Chamber

Oxygen Concentrator

HUMIDITY CONTROL SYSTEM

www.arduino.com

RECORDING DATA Pressure, Temperature, Humidity sensors

Membrane Housing

Humidity Chamber

Dry O2

Data Logging

Oxygen Concentrator

INITIAL RESULTS f Encountered Sensor Error f Not calibrated for varying pressure

f Relative Humidity = Function of pressure and temperature f Sensors not compensated for pressure

CONCLUSIONS f Initial tests indicate membrane does work f Membrane filter can provide a self-sustaining solution f Testing procedure adequate to benchmark prototype f Need better procedure for collecting humidity data

FUTURE WORK ´ Test membrane material in multiple conditions ´ Rework data collection ´ Revise filter design ´ Site team trip in January

ACKNOWLEDGEMENTS f Dr Brian Swartz, Advisor f Dr. John Spurrier, Client f Mr. Mabeta, Client f Mark Cole, Professional Correspondent f Jilean Schutz f Eric Listor f Chris Scheib f Barbara Ressler, Former Advisor

QUESTIONS

DRYING AGENT COMPARISON CHART Solution

Cost

Aftercooler

High

Mechanical Water Separator Low Deliquescent Dryer Fairly Low

Power Size Implementation Availability requirements Transportation Maintenance Fairly Intermediate Hard Common Large Varies Minimal

Small

Easy

Condenser Membrane Air Dryer

High

Large

Hard

High

Small

Easy

Common Not Common Fairly Common Fairly Common

Large

Hard

Desiccant

Low

Small

Easy

Common

None

Simple

Daily

Varies

Difficult

Weekly

Varies

Difficult

Monthly

None

Easy

Minimal

None

Easy

Moderate

DETERMINATION OF FAILURE MODE Temperature

Humidity

Altitude

Dust Level

DeVilbiss specifications

50 to 96 F

50 to 90%

10,000ft

Minimal

Conditions in Zambia

43 to 104F

60 to 95%

3000 to 10,000ft

High

²

Analysis and collaboration with DeVilbiss led us to conclude cause of failure is contamination of the sieve beds-through dust and humidity

f The humidity in Macha is typically below 80% relative humidity so as

long as we are able to reduce the humidity by 30% we believe we will not have problems with reduced concentrator lifetime