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University of Pittsburgh Senior Design - BioE1161. Redesign of ECMO Circuit Pressure Alarm System. Desiree Bonadonna Apryle Craig Laura Gilmour. Summary. Market review Problems Regulations Solutions Implementing the design Testing Future work. Need for Pressure Monitor Redesign. - PowerPoint PPT Presentation
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Redesign of ECMO Circuit Pressure Alarm System
Desiree Bonadonna
Apryle Craig
Laura Gilmour
University of PittsburghSenior 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 Breakdown Cost/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 870.2100
• Cardiovascular blood flowmeter
Predicate device:• Digibio Digital Blood Pressure Monitor
Electronic Regulations:• IEC 61000-4-2
• IEC 60601-1-2
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 = 1016-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 FactorsDecrease 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:•1st type produced larger error and required more circuitry•2nd 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 2nd 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 DesignA/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
Display vs. Voltage Input
y = 4712.9x - 21.333
R2 = 0.9982
y = 4707.9x - 20.935
R2 = 0.9982
y = 4711.9x - 20.195
R2 = 0.9983
-200
0
200
400
600
800
1000
0.00 0.05 0.10 0.15 0.20 0.25
Voltage Input (V)
Dis
play
Trial 1
Trial 2
Trial 3
Linear (Trial 3)
Linear (Trial 2)
Linear (Trial 1)
A/DTP-001 Results
PCTP-001 Results
PCTP-001 Results Trial 1
40
60
80
100
120
140
160
180
1 6 11
Sample
Pre
ssu
re (
mm
Hg
)
Manometer
Existing
Proposed
PCTP-001 Results
PCTP-001 Results Trial 2
0
50
100
150
200
250
300
0 5 10 15
Sample
Pre
ssu
re (
mm
Hg
)
Manometer
Existing
Proposed
Statistical Analysis
% error vs. known pressure
0.00
2.00
4.00
6.00
8.00
10.00
12.00
0 50 100 150 200 250 300
Pressure (mmHg)
% e
rror
Existing 1
Proposed 1
Existing 2
Proposed 2
Within the physiological range, the percent error of our device is lower than that of the currently used technology at CHP.
Statistical Analysis
Statistical Analysis of Deviation from Manometer
0
2
4
6
8
10
12
Mean Maximum
Pre
ssu
re (
mm
Hg
)
Exisitng 1
Proposed 1
Existing 2
Proposed 2
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 ManagementBioE 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
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?