Redesign of ECMO Circuit Pressure Alarm System Desiree Bonadonna Apryle Craig Laura Gilmour University of Pittsburgh Senior Design - BioE1161

Summary Market review Problems Regulations Solutions Implementing the design Testing Future work

Need for Pressure Monitor Redesign >120 Neonatal/Pediatric ECMO Centers in United States, increasing at a rate of ~2-5/year Growing number of private perfusion groups Sold through distributors and consultants Clots in the circuit are the most common mechanical complication (19%)

Expenditure may be between $80,000 and $100,000 per life saved Insurance reimbursement rate 60-70% Expense BreakdownCost/day Cost/patient ECMO$112 Disposables-$4,000 PICU bed$3,400 Physician$520 Respiratory+ Blood Bank+ Need for Pressure Monitor Redesign

Current system with roller pump is analog Current system with centrifugal is digital Redesign of the ECMO pressure system includes: Digital system for roller pump Additional pressure monitor Audible and visual alarm Users: Healthcare Workers Perfusionists ECMO Technicians Nurses Physicians

User Requirements Accurate to within +/- 15mmHg Refresh rate should not exceed 15 seconds Cost effective Safe and reliable Meets medical device regulations

Imprecise/inaccurate readings Convert to digital display Unknown post-heat exchanger pressure Add a third pressure gauge Requires constant monitoring Add audible and visual alarms Cluttered Design the device to hang on an IV pole Current ECMO Circuit Pressure Problems and Proposed Solutions:

Regulations Classification: Class II, CFR Cardiovascular blood flowmeter Predicate device: Digibio Digital Blood Pressure Monitor Electronic Regulations: IEC IEC

Goal #6: Improve the effectiveness of clinical alarm systems. a) Implement regular preventive maintenance and testing of alarm systems. b) Assure that alarms are activated with appropriate settings and are sufficiently audible with respect to distances and competing noise within the unit. JCAHO 2004 National Patient Safety Goals

Project Objectives and Features: Programmable Alarm Range “Assure that alarms are activated with appropriate settings…” Adjustable range for anthropometric differences and varying pathologies

Project Objectives and Features: Audible Alarm “…are sufficiently audible with respect to distances and competing noise within the unit.” Immediate notification of deviation Alarm=120dB Mean unit noise level = 80-89dB Startle response occurs at 30dB > mean noise Max Impulses = P/10 = 8,913

Project Objectives and Features: Visual Alarm Indicates which pressure is deviant from set range

Project Objectives and Features: Digital Display  Human Factors Decrease Human Error Ease of Use

Project Objectives and Features: Additional Pressure Indicator Pressure drop across heat exchanger can be determined and differentiated from patient

Design Alternatives Based on human factors

Design Alternatives

Engineering Technologies/Methodologies Technologies SolidWorks PSpice Rapid Prototyping Excel Methodologies Circuitry analysis Digital logic

Schematic of One Display Unit ADC & Display Visual Alarm Audible Alarm Op-Amp

2 Stages of A/D Converter Choice: 1 st type produced larger error and required more circuitry 2 nd type (ICL7107) included built-in display driver

3 Stages of Op-Amp Design: Scaled down 0-10V to 0-.2V and included another inverting op-amp Scaled down 0-1V to 0-.2V Eliminated 2 nd inverting op-amp since input was determined to be negative

Visual Alarm Highlights: Programmable range Comparators for high and low Switches to view range while adjusting it LED lights when out of range

Audible Alarm Highlights: Inverters needed between comparator and OR-gate OR-gate will be 6:1 in final design

Experimental Design A/DTP-001 Tests linearity of input voltage to output reading PCTP-001 Tests deviation of first-generation prototype from known pressure VACTP-001 Tests accuracy and independence of visual alarms AACTP-001 Tests accuracy and independence of audible alarm

A/DTP-001 Results

PCTP-001 Results

Statistical Analysis Within the physiological range, the percent error of our device is lower than that of the currently used technology at CHP.

Statistical Analysis

Competitive Analysis Analog Pressure Gauges Custom Made Digital Monitors COBE Cardiovascular SIII Pump Modules Console mounted control unit Strengths Smaller Not part of a kit Less expensive Hangs on IV pole Weaknesses Does not monitor all circuit information such as temperature, etc.

Team Roles

Project Management BioE 1160 GoalsBioE 1161 Accomplishments Model circuitry in PSpiceX Build working circuitX Test A/D ConverterX Test First Generation PrototypeX Add Visual AlarmX Test Addition of Visual AlarmX Implement Results of Testing Add Audible AlarmX Test Addition of Audible Alarm Implement Results of Testing Design CasingX

Future Work Further Testing Visual Alarm VACTP-001 Audible Alarm AACTP-001 Electrical Prototyping Second Generation Prototype

Acknowledgements University of Pittsburgh Department of Bioengineering Department of Electrical Engineering Michael Shaver, CCP Steven Jacobs, PhD Vikram Sundararaman

Questions?