Volumetric Airflow Gauge Guy Guimond, UPMC Center for Emergency Medicine Eric Reiss, Systems Manager, Swanson Institute Matthew Chakan Michael Nilo Justin.

Volumetric Airflow GaugeVolumetric Airflow Gauge

Guy Guimond, UPMC Center for Emergency MedicineGuy Guimond, UPMC Center for Emergency Medicine

Eric Reiss, Systems Manager, Swanson InstituteEric Reiss, Systems Manager, Swanson Institute

Matthew ChakanMatthew Chakan

Michael NiloMichael Nilo

Justin KiswardyJustin Kiswardy

University of Pittsburgh, Department of Bioengineering

April 10, 2007

Background & SignificanceBackground & Significance

Estimates of over 500k 911 calls daily, 35% Estimates of over 500k 911 calls daily, 35% involve cardio-pulmonary failureinvolve cardio-pulmonary failure11

Most common means of initiating breathing in-Most common means of initiating breathing in-field is use of mechanical ventilator (BVM)field is use of mechanical ventilator (BVM)

BVM systems used in patient transport w/in BVM systems used in patient transport w/in hospital or when true mechanical ventilators not hospital or when true mechanical ventilators not accessibleaccessible

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Background & SignificanceBackground & Significance

Most Healthcare Providers trained to “inflate based Most Healthcare Providers trained to “inflate based on resistance” w/ recommended introduced air @ on resistance” w/ recommended introduced air @ 400-600ml/cycle for average adult patient400-600ml/cycle for average adult patient22

As result of HP making on-site estimates, dangerous As result of HP making on-site estimates, dangerous air flow rates & pressures administered to patients air flow rates & pressures administered to patients have been observedhave been observed

Documented side-effects: lung tissue damage, lung Documented side-effects: lung tissue damage, lung compliance, gastric distension, regurgitationcompliance, gastric distension, regurgitation

Clinical Study showed ~40% patients experienced Clinical Study showed ~40% patients experienced gastric distension & 65% morbiditygastric distension & 65% morbidity33

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Project ObjectivesProject Objectives

Design a universal gauge capable of measuring Design a universal gauge capable of measuring airflow volumes that is easy to learn, operate, airflow volumes that is easy to learn, operate, and comprehend for the userand comprehend for the user

Device must be lightweight, portable, and Device must be lightweight, portable, and adaptable to most standard ventilators/BVM’s adaptable to most standard ventilators/BVM’s (Laerdal, Ambu, First Responder)(Laerdal, Ambu, First Responder)

Features adaptable for incorporation into a Features adaptable for incorporation into a learning environment (EMT classes)learning environment (EMT classes)

Design AlternativesDesign Alternatives

How will the airflow volume be measuredHow will the airflow volume be measured

• • pinwheel mechanism using highly pinwheel mechanism using highly compliant metal pincompliant metal pin

• • no external power source, sterilizable, no external power source, sterilizable, inexpensive manufacturing/ price-point, low-level inexpensive manufacturing/ price-point, low-level accuracy, malfunction issuesaccuracy, malfunction issues, , rotary gauge may rotary gauge may be difficult for user to readbe difficult for user to read

• electrical circuit similar to mass flow device, incorporating microcontroller, thermistors to measure airflow volume

• high-level of reproducible accuracy, requires external power source, computerized manufacturing, no autoclave, higher cost

Decision: electrical circuit minimizing error range & malfunction issues while maximizing ease of manufacturing

Disposable vs. reusable• many BVM systems are intended for one-time

use (pp. ~$20-50)

• disposable systems come w/ disposable attachments (PEEP gauge, pH indicator, etc.)

• reusable systems are able to be flashed via autoclave

• market allows much higher cost (pp. ~$100-400)

Decision: VAG is intended to be reused and may be sanitized w/ EtOH. Reusable device allows for higher production costs creating broader market.

Basic Component SelectionBasic Component Selection

Air flow sensor requirements:Air flow sensor requirements: Flow range > 1.6 L/sFlow range > 1.6 L/s Size < 38 inSize < 38 in33

Cleanable with medical products (e.g. Cleanable with medical products (e.g. Isopropanol)Isopropanol)

Display requirements:Display requirements: Two decimal place precision → 3-digitTwo decimal place precision → 3-digit Digit height > ¼”Digit height > ¼”

Microcontroller requirements:Microcontroller requirements: Relatively large RAM and ROMRelatively large RAM and ROM Enough pins to operate sensors and displaysEnough pins to operate sensors and displays

Component IntegrationComponent Integration

Electrical needs of basic components Electrical needs of basic components were identified and orderedwere identified and ordered 9V → 5V → 2.2V9V → 5V → 2.2V

Bridging components were selectedBridging components were selected Voltage Regulator (9V → 5V)Voltage Regulator (9V → 5V) Resistors (5V → 2.2V)Resistors (5V → 2.2V)

Component compatibility was Component compatibility was checked by verifying complementary checked by verifying complementary electrical characteristics (Aelectrical characteristics (AIIoutout < B < BIIinin))

Circuit SchematicCircuit Schematic

Extra Feature AdditionExtra Feature Addition

The air volume will change after reaching the The air volume will change after reaching the patient’s lungspatient’s lungs Charles’ Law:Charles’ Law: VV22 = V = V11 * (T * (T22/T/T11)) A thermistor was added to measure ambient A thermistor was added to measure ambient

temperaturetemperature The rate of artificial respiration is importantThe rate of artificial respiration is important

A Flashing LED metronome was added to indicate the A Flashing LED metronome was added to indicate the rescue breathing rate rescue breathing rate

The user needs to know when to replace the The user needs to know when to replace the batteriesbatteries Independent battery sampling and alert systems were Independent battery sampling and alert systems were

addedadded

Completed CircuitCompleted Circuit

CircuitCircuit OperationOperation

A C program was written for the A C program was written for the microcontroller to:microcontroller to: Measure:Measure:

Instantaneous air flow rateInstantaneous air flow rate Ambient temperatureAmbient temperature Battery voltagesBattery voltages

Display:Display: Cyclic air volume sumCyclic air volume sum Rescue breathing metronomeRescue breathing metronome Low battery voltagesLow battery voltages

Hold maximum cyclic air volume sum for easier user Hold maximum cyclic air volume sum for easier user readingreading

Reset air volume sum to zero for next cycleReset air volume sum to zero for next cycle

Product Engineering ObjectivesProduct Engineering Objectives

Build a casing thatBuild a casing that Prevents water from contacting the electrical circuitPrevents water from contacting the electrical circuit Diminishes mechanical damage to the circuitDiminishes mechanical damage to the circuit Seals the circuit and all small parts from the airflow Seals the circuit and all small parts from the airflow

pathpath Houses two 9V batteriesHouses two 9V batteries Fits the standard fittings of both the bag and valve Fits the standard fittings of both the bag and valve

attachmentsattachments distal tubing 15mmdistal tubing 15mm proximal tubing 23mm proximal tubing 23mm

Weighs less than 100g without batteriesWeighs less than 100g without batteries Is not cost prohibitiveIs not cost prohibitive

Prototype DevelopmentPrototype Development

Initial Initial prototypes prototypes made of waxmade of wax

Current SLA Current SLA prototypeprototype

Finished Finished productproduct

Project ManagementProject Management

Dec.Dec. || Jan.Jan. || Feb.Feb. || Mar.Mar. || Apr.Apr.

ProjectProject

IntroductionIntroduction

ConceptualConceptual

DesignDesign

ElectricalElectrical

DesignDesign

Circuit Circuit

ProgramProgram

MechanicalMechanical

DesignDesign

CasingCasing

DevelopmentDevelopment

V and VV and V

WrittenWritten

DeliverablesDeliverables

Responsibilites:Responsibilites:

Matt Chakan:Matt Chakan: Circuit Design and Fabrication, Microcontroller C Program Circuit Design and Fabrication, Microcontroller C Program

Michael Nilo:Michael Nilo: Mechanical Design and Fabrication using SolidWorksMechanical Design and Fabrication using SolidWorks

Justin Kiswardy:Justin Kiswardy: Verification and Validation, Written DeliverablesVerification and Validation, Written Deliverables

Quality Control ConsiderationsQuality Control Considerations

Risk Analysis Risk Analysis

• • Initial hazard analysisInitial hazard analysis

* identified two potentially catastrophic risks: * identified two potentially catastrophic risks: components of device break and enter patients airway and components of device break and enter patients airway and device malfunctions and blocks tubing. device malfunctions and blocks tubing.

* risks minimized by requiring that the user place * risks minimized by requiring that the user place device above the one-way valve, small components will not device above the one-way valve, small components will not have direct access to inside tubing (casing), ease of have direct access to inside tubing (casing), ease of incorporation and removal from BVM incorporation and removal from BVM

Function or Component

Failure Mode Effect on System Possible HazardsRisk Index

User Detection Means Applicable Controls

Electrical circuitryIncomplete circuit, resistor/thermistor malfunction

Display inoperableUser must rely on his/her judgement

BVisual inspection; realization of over/under inflation

Design most efficient circuit w/ few parts to minimize pot. hazard

LED malfunctionBurn out or incomplete circuit

Loss of power indicator/training mechanism

User doesn’t replace power source/device doesn’t work properly

B Realization of loss of powerSuggest time-frame for battery life & periodic maintenance

CasingDegradation due to repetitive use/exposure to extreme enviro.

Exposes circuitry/loose parts

Electrical malfunction B Visual inspectionStrong-lightweight material, recommend disposal after 6000 cycle use

Reset triggerMalfunction/no reset after each cycle

Improper volume display to user

Over/under inflation by user

C User awareness of airflow levelsUse microprocessor which minimizes error in reset function

LCD displayMalfunction/improper calibration

Incorrect volume display to user

Over/under inflation by user

CVisual inspection, user awareness of airflow

Recommend periodic maintenance

Tubing Crack/leak in tubing due to physical/enviro. damage

Compromised airflow to patient

Delayed/failure to resuscitate patient

D Visual/ auditory inspectionSet acceptable temp. range for device use, suggest periodic maintenance

• Failure Modes/Effects analysis

Risk LevelInterpretation

A Negligible risk

B Tolerable risk

C Undesirable risk

D Intolerable risk

Class I medical device • ISO 13485 rule 7.1 & 7.2 “non-invasive devices intended to act

as calibrator, monitor, or tester while connected to an active type II, III device…..is class I”

• VAG must comply with FDA’s Code of Federal Regulations 21.CFR.868.9 “ventilator tubing is device intended for use as conduit for channeling of gases between ventilator and patient during ventilation of patient…device is exempt from pre-market notification procedures”

Result: As class I device subject only to general controls. Must register device with the FDA and comply with good manufacturing techniques providing reasonable assurance of safety and effectiveness of product.

Verification & ValidationVerification & Validation

Optimize power sourceOptimize power source • • one vs. two 9V batteries: conduct tests to determine one vs. two 9V batteries: conduct tests to determine

difference in battery lifedifference in battery life• • one 9V=~15 min., two 9V=+2 hrs.one 9V=~15 min., two 9V=+2 hrs.• • analyze outcome vs. increased cost/inconvenience to useranalyze outcome vs. increased cost/inconvenience to user

Accuracy tests for displayAccuracy tests for display• • clinical studies show over-inflation by only 100ml can clinical studies show over-inflation by only 100ml can

cause gastric distensioncause gastric distension• • desired accuracy range +/- 50ml air desired accuracy range +/- 50ml air • • laerdal manikin w/ built in volume gaugelaerdal manikin w/ built in volume gauge

Survey administered to various doctors, nurses, and other Survey administered to various doctors, nurses, and other Healthcare Providers involved in the treatment/use with BVM Healthcare Providers involved in the treatment/use with BVM systems. systems.

• • Outcome of survey should allow the fine-tuning of the Outcome of survey should allow the fine-tuning of the VAG (ie., the elimination or addition of features) and will be easier VAG (ie., the elimination or addition of features) and will be easier to understand specific market needsto understand specific market needs

Features & BenefitsFeatures & Benefits

Summary of featuresSummary of features

• • a cost-effective volumetric airflow gauge that can a cost-effective volumetric airflow gauge that can be incorporated into any standard BVM systembe incorporated into any standard BVM system

• • provides numeric display of air volume introduced provides numeric display of air volume introduced to patient during in-field/hospital rescueto patient during in-field/hospital rescue

• • provides high level of accuracy (w/in +/-50ml)provides high level of accuracy (w/in +/-50ml)

• • may be disinfected for repetitive usemay be disinfected for repetitive use

• • eliminates comorbidity associated w/ over/under eliminates comorbidity associated w/ over/under inflation (gastric distension, lung damage, regurgitation), inflation (gastric distension, lung damage, regurgitation), reduces hospital stay/costsreduces hospital stay/costs

• • built in LED metronome may be used for training built in LED metronome may be used for training purposes/user awarenesspurposes/user awareness

Potential disadvantagesPotential disadvantages

• • periodic battery replacement/testing periodic battery replacement/testing (increases maintenance tasks required of user)(increases maintenance tasks required of user)

• • non-sterilizable (limit market size)non-sterilizable (limit market size)

• • does not account for air escaping face/mask does not account for air escaping face/mask sealseal

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Market PotentialMarket Potential

Current competitionCurrent competition

• • mechanical transport ventilators: manually mechanical transport ventilators: manually set the desired flow rate, pulsatile flow based on PIP set the desired flow rate, pulsatile flow based on PIP and PEEP, bulky (20-40 lbs.), expensive (>$1500)and PEEP, bulky (20-40 lbs.), expensive (>$1500)

• • hand-held monitors: battery operated, hand-held monitors: battery operated, lightweight, complicated setup, expensive (+$400)lightweight, complicated setup, expensive (+$400)

• • Future competition?Future competition?

• • r&d geared towards design of eff.r&d geared towards design of eff.

volume gaugevolume gauge

Market size & pricingMarket size & pricing

• • 2005 sales: Zoll med. ~$248 mil., Ambu 2005 sales: Zoll med. ~$248 mil., Ambu ~$116 (respiratory care)~$116 (respiratory care)

• • more than $1.3 billion spent (US) on more than $1.3 billion spent (US) on ventilators, oxygen therapy systems, and airway ventilators, oxygen therapy systems, and airway management devices in 2004management devices in 2004

• • reusable PEEP valves $100-200, disposable reusable PEEP valves $100-200, disposable pH indicators $50-100pH indicators $50-100

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8

9 10

Moving ForwardMoving Forward

Finish testing and validationFinish testing and validation

• • make necessary adjustments according to make necessary adjustments according to results of surveyresults of survey

• • testing through UPMC Center for testing through UPMC Center for Emergency MedicineEmergency Medicine

Design packaging and Design packaging and instruction/troubleshooting manual instruction/troubleshooting manual

Submit SBIR phase I proposalSubmit SBIR phase I proposal

AcknowledgementsAcknowledgements

Mr. Guy Guimond & UPMC Center for Mr. Guy Guimond & UPMC Center for Emergency Medicine Emergency Medicine

Dr. Hal Wrigley and Dr. Linda Baker for Dr. Hal Wrigley and Dr. Linda Baker for providing fundingproviding funding

Department of Bioengineering, University of Department of Bioengineering, University of PittsburghPittsburgh

Thank YouThank YouDepartment of Bioengineering University of Pittsburgh

Flow Rate vs. Voltage RatioFlow Rate vs. Voltage Ratio

Q = 1024.41819(Vo/Vi)5 - 1221.16987(Vo/Vi)4 + 577.76204(Vo/Vi)3 - 128.05109(Vo/Vi)2 + 14.86963(Vo/Vi) - 0.67579

R2 = 0.99993

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Voltage Ratio (Vout / Vin)

Flo

w R

ate

(S

LP

S)

Printed Circuit Board Printed Circuit Board DesignDesign

OverviewOverview

Incorporation of volumetric airflow gauge into a Incorporation of volumetric airflow gauge into a standard mechanical ventilator/bag-valve-mask standard mechanical ventilator/bag-valve-mask system (BVM)system (BVM)

Intended to provide user w/ volume of air Intended to provide user w/ volume of air introduced to patient with each squeeze of the introduced to patient with each squeeze of the bag bag

Intended users include: EMT specialists, trained Intended users include: EMT specialists, trained nursing staff, doctors and other healthcare nursing staff, doctors and other healthcare providersproviders

CitationsCitations

CitationsCitations1. 1. Davidoff F, DeAngelis CD, Drazen JM, Hoey J, Hojgaard L, Horton R (2006). Davidoff F, DeAngelis CD, Drazen JM, Hoey J, Hojgaard L, Horton R (2006). Emergency Cardiac Emergency Cardiac

CareCare. . Prehospital Emergency CarePrehospital Emergency Care; Vol. 10; 36-48.; Vol. 10; 36-48.2. 2. Kuhns R., Davis J. (2004). Kuhns R., Davis J. (2004). A work measurement evaluation of emergency medical services. A work measurement evaluation of emergency medical services.

IIE Annual Conference and Exhibition 2004; 3431-3467.IIE Annual Conference and Exhibition 2004; 3431-3467.3. 3. American Heart Association (2005). American Heart Association (2005). AHA guidelines for CPR and ECC. AHA guidelines for CPR and ECC. Vol. 112; Issue 4; 14-Vol. 112; Issue 4; 14-

20; 126-131. 20; 126-131. 4. 4. Von Goedecke A, Wagner-Berger H, Stadlbauer K, Krismer A, Jakubasko C, Bratschke C, Wnzel V, Von Goedecke A, Wagner-Berger H, Stadlbauer K, Krismer A, Jakubasko C, Bratschke C, Wnzel V,

Keller C. (2004). Keller C. (2004). Effects of decreasing peak flow rate on stomach inflation during bag-Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation.valve-mask ventilation. ResuscitationResuscitation; 63: 131–136.; 63: 131–136.

5. 5. International Liaison Committee on Resuscitation. 2005 International Liaison Committee on Resuscitation. 2005 International Consensus on International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations.Treatment Recommendations. Circulation. Circulation. 2005; 112: III-1–III-136.2005; 112: III-1–III-136.

6. 6. Nolan J. (2001). Nolan J. (2001). Prehospital and resuscitative airway care: should the gold standard be Prehospital and resuscitative airway care: should the gold standard be reassessed? reassessed? Current Opinion in Critical CareCurrent Opinion in Critical Care; ; 77: 413–421.: 413–421.

7.7. Wenzel V, Keller C, Ahamed H, Volker D, Lindner K, Brimacombe J (1999). Wenzel V, Keller C, Ahamed H, Volker D, Lindner K, Brimacombe J (1999). Effects on smaller Effects on smaller tidal Volumes during basic life support ventilation in patients with respiratory arrest: tidal Volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk?good ventilation, less risk? ResuscitationResuscitation; 43: 25–29.; 43: 25–29.

8.8. Sheperd C.,(2006). Sheperd C.,(2006). Reflection on a patient's airway management during a ward-based Reflection on a patient's airway management during a ward-based resuscitation. resuscitation. Nursing in Critical Care; Nursing in Critical Care; Vol. 11, 217-2Vol. 11, 217-2 23 23

9.9. Life Medical Supplier, Life Medical Supplier, www.lifemedical.comwww.lifemedical.com10.10. Miraclemed, Miraclemed, www.miraclemed.comwww.miraclemed.com, Seattle, WA., Seattle, WA.