Transcript BE1161 - Final Presentation (Apr. 13, 2004)

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
• >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%)
Need for Pressure Monitor Redesign
• Expenditure may be between $80,000 and
$100,000 per life saved
• Insurance reimbursement rate 60-70%
Expense
Breakdown
ECMO
Disposables
Cost/day
Cost/patient
$112
-
PICU bed
$3,400
Physician
$520
Respiratory
+
Blood Bank
+
$4,000
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
User Requirements
• Accurate to within +/- 15mmHg
• Refresh rate should not exceed
15 seconds
• Cost effective
• Safe and reliable
• Meets medical device
regulations
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
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
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.
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 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
Methodologies
• SolidWorks
• Circuitry
analysis
• PSpice
• Rapid
Prototyping
• Excel
• Digital logic
Schematic of One Display
Unit
Op-Amp
ADC &
Display
Audible Alarm
Visual Alarm
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 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
Display vs. Voltage Input
Trial 1
Trial 2
Trial 3
1000
Linear (Trial 3)
800
Linear (Trial 2)
Linear (Trial 1)
Display
600
400
200
0
0.00
-200
0.05
0.10
0.15
Voltage Input (V)
0.20
y = 4711.9x - 20.195
R2 = 0.9983
0.25 y = 4707.9x - 20.935
R2 = 0.9982
y = 4712.9x - 21.333
R2 = 0.9982
PCTP-001 Results
PCTP-001 Results Trial 1
180
Pressure (mmHg)
160
140
Manometer
120
Existing
100
Proposed
80
60
40
1
6
Sample
11
PCTP-001 Results
PCTP-001 Results Trial 2
Pressure (mmHg)
300
250
200
Manometer
150
Existing
Proposed
100
50
0
0
5
10
Sample
15
Statistical Analysis
% error vs. known pressure
Within the physiological
range, the percent error of
our device is lower than
that of the currently used
technology at CHP.
12.00
10.00
% error
8.00
Existing 1
Proposed 1
6.00
Existing 2
Proposed 2
4.00
2.00
0.00
0
50
100
150
Pressure (mmHg)
200
250
300
Statistical Analysis
Statistical Analysis of Deviation from Manometer
12
Pressure (mmHg)
10
8
Exisitng 1
Proposed 1
6
Existing 2
Proposed 2
4
2
0
Mean
Maximum
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 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?