Transcript Wireless Auscultation Device for Continuous Monitoring of Heart

Wireless Auscultation Device for Continuous
Monitoring of Heart Sounds
Danielle Manley | Stephen Krammin | Mateusz Koper
Department of Biomedical Engineering
Lawrence Technological University
Faculty Advisors: Dr. Gerald LeCarpentier & Dr. Mansoor Nasir
Technical Advisor: Professor Kenneth Cook
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What is Auscultation?
Auscultation: Act of listening to body sounds as a part of making a
medical diagnosis
● Occurs during almost all hospital visits
● Auscultate heart, lungs, intestinal sounds
● Evaluate certain sound characteristics:
o Frequency
o Intensity
o Duration
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Heart Sounds
● Heart Sounds
o Blood flow through the heart valves
o Frequency range from 20-650 Hz
o Abnormal sounds interpreted as potential murmurs
● Most common murmurs:
o Regurgitation
o Stenosis
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Current Methods
Mechanical Stethoscope:
Cheap $15-100
No Power Necessary
Electronic
Stethoscope:
Electrical
Stethoscopes
Filter Noise
Amplify Sounds
Poor Sound Quality
Excess outside noise
Not Handsfree
Expensive $250-1000
Power Necessary
Not Handsfree
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Stethoscope Limitations
Problem: Stethoscopes do not monitor sounds continuously and they
are not hands free
Continuous heart sound monitoring would be very useful for the
following applications:
● Diagnose Patients with Infectious Diseases
● Pharmaceutical Interventions
● Multiple Patient Monitoring
● Telemedicine
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Project & Design Goals
● Wireless auscultation device
● Remove need for physician’s
presence
● Create Bluetooth capable
device
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Untethered
Low-power
Low-cost
User Friendly
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Design Process
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Sound Pick-up
● Used a cheap stethoscope
head and PVC tubing
● Placed an electret condenser
microphone into end of
tubing
● Two wires connected from
microphone to circuit’s
input and ground
Microphone
Placement
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Circuitry
LPF
Signal Amplification
Voltage Offset
HPF
Microphone
Bias Network
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Bode Plot
High Pass: 15 Hz
Low Pass: 964 Hz
Bandwidth:
15 Hz - 964 Hz
Gain = 75
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A/D Conversion
● Arduino Uno microcontroller with SD card shield
● Arduino program developed:
o Sampling frequency of
1000 points/sec
o Analog voltages read and
converted to bytes (0-1023)
o Data stored into a text file
created on the SD card
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Data Transfer
● Laptop paired to Bluetooth device (HC-05 Transceiver)
● Similar program developed in MATLAB
o SD card read and Bluetooth transfer of
data into MATLAB
o Bytes converted to voltages and stored
into an array
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Data Analysis
● Matlab:
o Plotting
o Fast-Fourier Transform (FFT)
 Frequency components
o Digital filtering
 Signal processing toolbox
o Audio playback
 Sound function
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Verification of Device
CH #1
Biopac Electronic
Stethoscope
CH #2
Signal Cable
Auscultation Circuitry
Biopac Display
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Our Stethoscope vs Biopac Stethoscope
● First peak - S1 heart sound (“Lub”)
● Second peak - S2 heart sound (“Dub”)
Red = Our Stethoscope
Blue = Biopac Stethoscope
● Similar results support our device functionality
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Biopac: Healthy vs Abnormal
● Our device is capable of depicting healthy and abnormal heartbeats
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Biopac vs Arduino: Silence
● Seems like Arduino is collecting more noise than Biopac
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Biopac vs Arduino: Talking
● Seems like Arduino is collecting more noise than Biopac
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Biopac vs Arduino: Filtered Talking
● Signal is much cleaner compared to unfiltered talking
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Discussion and Conclusion
● Wireless prototype created that can collect and send heart sounds
using Bluetooth
● MATLAB program developed that can process and playback
captured heart sounds
● Our device can compete with both mechanical and electrical
stethoscopes in terms of:
o Ease of use
o Sound quality
o Cost
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Future Improvements
● Test sound isolation materials
● Miniaturize device
● Incorporate adhesive
● Central monitoring system
● Other body sounds
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Miniaturizing the Device
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Printed Circuit Board
Piezoelectric Transducer
Smaller Batteries
Mini Microcontroller
Estimated price of our stethoscope ≈ $50
(Mechanical: $15+ Electronic: $250+)
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Roles and Responsibilities
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Timeline
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Acknowledgments
Faculty Advisors:
● Dr. Gerald LeCarpentier:
o Arduino Programming
o Providing Arduino Uno
● Dr. Mansoor Nasir:
o Matlab Programming
o Providing Various Materials
Technical Advisor:
● Professor Kenneth Cook:
o Circuit Development & Testing
o Providing Various Materials
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References
● http://www.electronics-lab.com/blog/?p=20744
● https://www.circuitsathome.com/products-page/power-supplies/3-3v-to5v-600ma-dc-dc-converter-bare-pcb
● http://www.explainthatstuff.com/piezoelectricity.html
● http://www.cdc.gov/nchs/data/nhsr/nhsr007.pdf
● http://www.audiologyonline.com/articles/amplified-stethoscope-optionsfor-professionals-860
● http://www.nlm.nih.gov/medlineplus/ency/article/002226.htm
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Questions?
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ECG vs Heart Sounds
● ECG provides insight into the electrical activity of the heart
o Used primarily to determine arrhythmias
● Heart sounds provide insight on the structure
o Health of heart valves
o Thickening of ventricular septum
o Fluid build up in pericardium
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