Redesign of ECMO Circuit Pressure Alarm System

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Redesign of ECMO Circuit Pressure Alarm System
University of Pittsburgh Senior Design - BioE1161

• Desiree Bonadonna
• Apryle Craig
• Laura Gilmour

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Summary

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

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Need for Pressure Monitor Redesign

• gt120 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)

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Need for Pressure Monitor Redesign

• Expenditure may be between 80,000 and 100,000
  per life saved
• Insurance reimbursement rate 60-70

Expense Breakdown Cost/day Cost/patient
ECMO 112  
Disposables - 4,000
PICU bed 3,400  
Physician 520  
Respiratory  
Blood Bank  
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• Users Healthcare Workers
• Perfusionists
• ECMO Technicians
• Nurses
• Physicians

• 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

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User Requirements

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

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Current ECMO Circuit Pressure Problems and
Proposed Solutions

• 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

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Regulations

• Classification
• Class II, CFR 870.2100
• Cardiovascular blood flowmeter
• Predicate device
• Digibio Digital Blood Pressure Monitor
• Electronic Regulations
• IEC 61000-4-2
• IEC 60601-1-2

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JCAHO 2004 National Patient Safety Goals

• 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.

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Project Objectives and Features Programmable
Alarm Range

• Assure that alarms are activated with
  appropriate settings
• Adjustable range for anthropometric differences
  and varying pathologies

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Project Objectives and Features Audible Alarm

• are sufficiently audible with respect to
  distances and competing noise within the unit.
• Immediate notification of deviation
• Alarm120dB
• Mean unit noise level 80-89dB
• Startle response occurs at 30dB gt mean noise
• Max Impulses 1016-P/10 8,913

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Project Objectives and FeaturesVisual Alarm

• Indicates which pressure is deviant from set range

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Project Objectives and Features Digital Display
?
Human Factors Decrease Human Error Ease of Use
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Project Objectives and Features Additional
Pressure Indicator

• Pressure drop across heat exchanger can be
  determined and differentiated from patient

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Design Alternatives
Based on human factors
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Design Alternatives
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Engineering Technologies/Methodologies

• Technologies
• SolidWorks
• PSpice
• Rapid Prototyping
• Excel

• Methodologies
• Circuitry analysis
• Digital logic

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Schematic of One Display Unit
ADC Display
Op-Amp
Audible Alarm
Visual Alarm
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• 2 Stages of A/D Converter Choice
• 1st type produced larger error and required more
  circuitry
• 2nd type (ICL7107) included built-in display
  driver

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• 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 2nd inverting op-amp since input was
  determined to be negative

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

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• Audible Alarm Highlights
• Inverters needed between comparator and OR-gate
• OR-gate will be 61 in final design

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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

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A/DTP-001 Results
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PCTP-001 Results
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PCTP-001 Results
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Statistical Analysis
Within the physiological range, the percent error
of our device is lower than that of the currently
used technology at CHP.
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Statistical Analysis
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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.

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Team Roles
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Project Management
BioE 1160 Goals BioE 1161 Accomplishments
Model circuitry in PSpice X
Build working circuit X
Test A/D Converter X
Test First Generation Prototype X
Add Visual Alarm X
Test Addition of Visual Alarm X
Implement Results of Testing
Add Audible Alarm X
Test Addition of Audible Alarm
Implement Results of Testing
Design Casing X
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Future Work

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

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Acknowledgements

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

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Questions?