Volumetric Airflow Gauge Guy Guimond, UPMC Center for Emergency Medicine Eric Reiss, Systems Manager, Swanson Institute Matthew Chakan Michael Nilo Justin Kiswardy University of Pittsburgh, Department of Bioengineering April 10, 2007

Background & Significance Estimates of over 500k 911 calls daily, 35% involve cardio- pulmonary failure 1 Estimates of over 500k 911 calls daily, 35% involve cardio- pulmonary failure 1 Most common means of initiating breathing in-field is use of mechanical ventilator (BVM) Most common means of initiating breathing in-field is use of mechanical ventilator (BVM) BVM systems used in patient transport w/in hospital or when true mechanical ventilators not accessible BVM systems used in patient transport w/in hospital or when true mechanical ventilators not accessible 4

Background & Significance Most Healthcare Providers trained to “inflate based on resistance” w/ recommended introduced ml/cycle for average adult patient 2 Most Healthcare Providers trained to “inflate based on resistance” w/ recommended introduced ml/cycle for average adult patient 2 As result of HP making on-site estimates, dangerous air flow rates & pressures administered to patients have been observed As result of HP making on-site estimates, dangerous air flow rates & pressures administered to patients have been observed Documented side-effects: lung tissue damage, lung compliance, gastric distension, regurgitation Documented side-effects: lung tissue damage, lung compliance, gastric distension, regurgitation Clinical Study showed ~40% patients experienced gastric distension & 65% morbidity 3 Clinical Study showed ~40% patients experienced gastric distension & 65% morbidity 3 5

Project Objectives Design a universal gauge capable of measuring airflow volumes that is easy to learn, operate, and comprehend for the user Design a universal gauge capable of measuring airflow volumes that is easy to learn, operate, and comprehend for the user Device must be lightweight, portable, and adaptable to most standard ventilators/BVM’s (Laerdal, Ambu, First Responder) Device must be lightweight, portable, and adaptable to most standard ventilators/BVM’s (Laerdal, Ambu, First Responder) Features adaptable for incorporation into a learning environment (EMT classes) Features adaptable for incorporation into a learning environment (EMT classes)

Design Alternatives How will the airflow volume be measured How will the airflow volume be measured pinwheel mechanism using highly compliant metal pin pinwheel mechanism using highly compliant metal pin no external power source, sterilizable, inexpensive manufacturing/ price-point, low-level accuracy, malfunction issues, rotary gauge may be difficult for user to read no external power source, sterilizable, inexpensive manufacturing/ price-point, low-level accuracy, malfunction issues, rotary gauge may be 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. ~$20-50) disposable systems come w/ disposable attachments (PEEP gauge, pH indicator, etc.) reusable systems are able to be flashed via autoclave market allows much higher cost (pp. ~$ ) 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 Selection Air flow sensor requirements: Air flow sensor requirements: Flow range > 1.6 L/s Flow range > 1.6 L/s Size < 38 in 3 Size < 38 in 3 Cleanable with medical products (e.g. Isopropanol) Cleanable with medical products (e.g. Isopropanol) Display requirements: Display requirements: Two decimal place precision → 3-digit Two decimal place precision → 3-digit Digit height > ¼” Digit height > ¼” Microcontroller requirements: Microcontroller requirements: Relatively large RAM and ROM Relatively large RAM and ROM Enough pins to operate sensors and displays Enough pins to operate sensors and displays

Component Integration Electrical needs of basic components were identified and ordered Electrical needs of basic components were identified and ordered 9V → 5V → 2.2V 9V → 5V → 2.2V Bridging components were selected Bridging components were selected Voltage Regulator (9V → 5V) Voltage Regulator (9V → 5V) Resistors (5V → 2.2V) Resistors (5V → 2.2V) Component compatibility was checked by verifying complementary electrical characteristics (A I out < B I in ) Component compatibility was checked by verifying complementary electrical characteristics (A I out < B I in )

Circuit Schematic

Extra Feature Addition The air volume will change after reaching the patient’s lungs The air volume will change after reaching the patient’s lungs Charles’ Law:V 2 = V 1 * (T 2 /T 1 ) Charles’ Law:V 2 = V 1 * (T 2 /T 1 ) A thermistor was added to measure ambient temperature A thermistor was added to measure ambient temperature The rate of artificial respiration is important The rate of artificial respiration is important A Flashing LED metronome was added to indicate the rescue breathing rate A Flashing LED metronome was added to indicate the rescue breathing rate The user needs to know when to replace the batteries The user needs to know when to replace the batteries Independent battery sampling and alert systems were added Independent battery sampling and alert systems were added

Completed Circuit

Circuit Operation A C program was written for the microcontroller to: A C program was written for the microcontroller to: Measure: Measure: Instantaneous air flow rate Instantaneous air flow rate Ambient temperature Ambient temperature Battery voltages Battery voltages Display: Display: Cyclic air volume sum Cyclic air volume sum Rescue breathing metronome Rescue breathing metronome Low battery voltages Low battery voltages Hold maximum cyclic air volume sum for easier user reading Hold maximum cyclic air volume sum for easier user reading Reset air volume sum to zero for next cycle Reset air volume sum to zero for next cycle

Product Engineering Objectives Build a casing that Build a casing that Prevents water from contacting the electrical circuit Prevents water from contacting the electrical circuit Diminishes mechanical damage to the circuit Diminishes mechanical damage to the circuit Seals the circuit and all small parts from the airflow path Seals the circuit and all small parts from the airflow path Houses two 9V batteries Houses two 9V batteries Fits the standard fittings of both the bag and valve attachments Fits the standard fittings of both the bag and valve attachments distal tubing 15mm distal tubing 15mm proximal tubing 23mm proximal tubing 23mm Weighs less than 100g without batteries Weighs less than 100g without batteries Is not cost prohibitive Is not cost prohibitive

Prototype Development Initial prototypes made of wax Initial prototypes made of wax Current SLA prototype Current SLA prototype Finished product Finished product

Project Management Dec.|Jan.|Feb.|Mar.|Apr. ProjectIntroductionConceptualDesignElectricalDesignCircuitProgramMechanicalDesignCasingDevelopment V and V WrittenDeliverablesResponsibilites: Matt Chakan:Circuit Design and Fabrication, Microcontroller C Program Michael Nilo:Mechanical Design and Fabrication using SolidWorks Justin Kiswardy:Verification and Validation, Written Deliverables

Quality Control Considerations Risk Analysis Risk Analysis Initial hazard analysis Initial hazard analysis * identified two potentially catastrophic risks: components of device break and enter patients airway and device malfunctions and blocks tubing. * risks minimized by requiring that the user place device above the one- way valve, small components will not have direct access to inside tubing (casing), ease of incorporation and removal from BVM Function or Component Failure ModeEffect on SystemPossible Hazards Risk Index User Detection MeansApplicable Controls Electrical circuitry Incomplete circuit, resistor/thermistor malfunction Display inoperable User must rely on his/her judgement B Visual inspection; realization of over/under inflation Design most efficient circuit w/ few parts to minimize pot. hazard LED malfunction Burn out or incomplete circuit Loss of power indicator/training mechanism User doesn’t replace power source/device doesn’t work properly BRealization of loss of power Suggest time-frame for battery life & periodic maintenance Casing Degradation due to repetitive use/exposure to extreme enviro. Exposes circuitry/loose parts Electrical malfunctionBVisual inspection Strong-lightweight material, recommend disposal after 6000 cycle use Reset trigger Malfunction/no reset after each cycle Improper volume display to user Over/under inflation by user CUser awareness of airflow levels Use microprocessor which minimizes error in reset function LCD display Malfunction/improper calibration Incorrect volume display to user Over/under inflation by user C Visual 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 DVisual/ auditory inspection Set acceptable temp. range for device use, suggest periodic maintenance Failure Modes/Effects analysis Risk Level Interpretation ANegligible risk BTolerable risk CUndesirable risk DIntolerable risk Class I medical device ISO 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 “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 & Validation Optimize power source Optimize power source one vs. two 9V batteries: conduct tests to determine difference in battery life one vs. two 9V batteries: conduct tests to determine difference 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 user analyze outcome vs. increased cost/inconvenience to user Accuracy tests for display Accuracy tests for display clinical studies show over-inflation by only 100ml can cause gastric distension clinical studies show over-inflation by only 100ml can cause gastric distension desired accuracy range +/- 50ml air desired accuracy range +/- 50ml air laerdal manikin w/ built in volume gauge laerdal manikin w/ built in volume gauge Survey administered to various doctors, nurses, and other Healthcare Providers involved in the treatment/use with BVM systems. Survey administered to various doctors, nurses, and other Healthcare Providers involved in the treatment/use with BVM systems. Outcome of survey should allow the fine-tuning of the VAG (ie., the elimination or addition of features) and will be easier to understand specific market needs Outcome of survey should allow the fine-tuning of the VAG (ie., the elimination or addition of features) and will be easier to understand specific market needs

Features & Benefits Summary of features Summary of features a cost-effective volumetric airflow gauge that can be incorporated into any standard BVM system a cost-effective volumetric airflow gauge that can be incorporated into any standard BVM system provides numeric display of air volume introduced to patient during in-field/hospital rescue provides numeric display of air volume introduced to 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 use may be disinfected for repetitive use eliminates comorbidity associated w/ over/under inflation (gastric distension, lung damage, regurgitation), reduces hospital stay/costs eliminates comorbidity associated w/ over/under inflation (gastric distension, lung damage, regurgitation), reduces hospital stay/costs built in LED metronome may be used for training purposes/user awareness built in LED metronome may be used for training purposes/user awareness Potential disadvantages Potential disadvantages periodic battery replacement/testing (increases maintenance tasks required of user) periodic battery replacement/testing (increases maintenance tasks required of user) non-sterilizable (limit market size) non-sterilizable (limit market size) does not account for air escaping face/mask seal does not account for air escaping face/mask seal 6

Market Potential Current competition Current competition mechanical transport ventilators: manually set the desired flow rate, pulsatile flow based on PIP and PEEP, bulky (20-40 lbs.), expensive (>$1500) mechanical transport ventilators: manually set the desired flow rate, pulsatile flow based on PIP and PEEP, bulky (20-40 lbs.), expensive (>$1500) hand-held monitors: battery operated, lightweight, complicated setup, expensive (+$400) hand-held monitors: battery operated, lightweight, complicated setup, expensive (+$400) Future competition? Future competition? r&d geared towards design of eff. r&d geared towards design of eff. volume gauge Market size & pricing Market size & pricing 2005 sales: Zoll med. ~$248 mil., Ambu ~$116 (respiratory care) 2005 sales: Zoll med. ~$248 mil., Ambu ~$116 (respiratory care) more than $1.3 billion spent (US) on ventilators, oxygen therapy systems, and airway management devices in 2004 more than $1.3 billion spent (US) on ventilators, oxygen therapy systems, and airway management devices in 2004 reusable PEEP valves $ , disposable pH indicators $ reusable PEEP valves $ , disposable pH indicators $

Moving Forward Finish testing and validation Finish testing and validation make necessary adjustments according to results of survey make necessary adjustments according to results of survey testing through UPMC Center for Emergency Medicine testing through UPMC Center for Emergency Medicine Design packaging and instruction/troubleshooting manual Design packaging and instruction/troubleshooting manual Submit SBIR phase I proposal Submit SBIR phase I proposal

Acknowledgements Mr. Guy Guimond & UPMC Center for Emergency Medicine Mr. Guy Guimond & UPMC Center for Emergency Medicine Dr. Hal Wrigley and Dr. Linda Baker for providing funding Dr. Hal Wrigley and Dr. Linda Baker for providing funding Department of Bioengineering, University of Pittsburgh Department of Bioengineering, University of Pittsburgh Thank You Department of Bioengineering University of Pittsburgh

Flow Rate vs. Voltage Ratio

Printed Circuit Board Design

Overview Incorporation of volumetric airflow gauge into a standard mechanical ventilator/bag-valve-mask system (BVM) Incorporation of volumetric airflow gauge into a standard mechanical ventilator/bag-valve-mask system (BVM) Intended to provide user w/ volume of air introduced to patient with each squeeze of the bag Intended to provide user w/ volume of air introduced to patient with each squeeze of the bag Intended users include: EMT specialists, trained nursing staff, doctors and other healthcare providers Intended users include: EMT specialists, trained nursing staff, doctors and other healthcare providers

Citations Citations 1. Davidoff F, DeAngelis CD, Drazen JM, Hoey J, Hojgaard L, Horton R (2006). Emergency Cardiac Care. Prehospital Emergency Care; Vol. 10; Kuhns R., Davis J. (2004). A work measurement evaluation of emergency medical services. IIE Annual Conference and Exhibition 2004; American Heart Association (2005). AHA guidelines for CPR and ECC. Vol. 112; Issue 4; 14-20; Von Goedecke A, Wagner-Berger H, Stadlbauer K, Krismer A, Jakubasko C, Bratschke C, Wnzel V, Keller C. (2004). Effects of decreasing peak flow rate on stomach inflation during bag-valve-mask ventilation. Resuscitation; 63: 131– International Liaison Committee on Resuscitation International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science With Treatment Recommendations. Circulation. 2005; 112: III-1–III Nolan J. (2001). Prehospital and resuscitative airway care: should the gold standard be reassessed? Current Opinion in Critical Care; 7: 413– Wenzel V, Keller C, Ahamed H, Volker D, Lindner K, Brimacombe J (1999). Effects on smaller tidal Volumes during basic life support ventilation in patients with respiratory arrest: good ventilation, less risk? Resuscitation; 43: 25– Sheperd C.,(2006). Reflection on a patient's airway management during a ward-based resuscitation. Nursing in Critical Care; Vol. 11, Life Medical Supplier, Miraclemed, Seattle, WA.