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Baby Breathing Monitor What were we thinking? Senior Design Project #41 Spring 2001 Adnan Bajowala Julie Cherian Mitesh Parikh

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Baby Breathing Monitor What were we thinking? Senior Design Project #41 Spring 2001 Adnan Bajowala Julie Cherian Mitesh Parikh. Introduction. Why Measure Breathing Rate? Infants are at risk of experiencing an apnea when sleeping Many times parents are unaware of the apnea

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Baby Breathing MonitorWhat were we thinking?Senior Design Project #41Spring 2001Adnan BajowalaJulie CherianMitesh Parikh

introduction
Introduction
  • Why Measure Breathing Rate?
    • Infants are at risk of experiencing an apnea when sleeping
    • Many times parents are unaware of the apnea
    • A low cost, reliable, and non-intrusive breathing monitor not available now
medical background
Medical Background
  • Definition of Apnea
    • No breath is taken within a period of 15 seconds
  • Facts
    • Adult breathing rate = 15 breaths/minute
    • Baby breathing rate = 30-50 breaths/minute
  • Significance
    • The baby has missed 12.5 breaths if apnea occurs
    • This can be a serious problem
what s out there now
What’s Out There Now?
  • Monitoring by Impedance Nemography
    • Breathing is measured by movement of electrodes
    • Unreliable and expensive
what we wanted to do
What We Wanted to Do
  • Monitor both breathing and heart rate
  • Breathing rate would be monitored using a microphone system
  • Heart rate would be monitored using a wireless system
  • Control of both systems using a microcontroller
what was sane to do
What Was Sane to Do
  • Breathing monitor
    • Implemented using a microphone, PC sound card, and LABVIEW software
  • No heart rate monitor
    • Overly ambitious for the time frame
    • Similar to a previous senior design project
what s the big idea
What’s the Big Idea?
  • Find the characteristic frequency range of breathing
  • Use a filter to eliminate everything else
  • Use what’s left to decide if the baby is breathing normally
    • Sound an alarm if apnea occurs
  • It all sounds so simple, doesn’t it?
finding the frequency range
Finding the Frequency Range
  • Idea One
    • Look for existing data
    • It’s not there!
  • Idea Two
    • Use a spectrum analyzer
    • Problem:
      • All microphone outputs were too noisy
    • Result:
      • Cannot detect breathing signal
      • Need amplification and filtering
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Idea Three
    • Observation
      • Common baby monitors pick up the sound of a baby breathing
    • So…
      • Use their microphone to obtain the signal!
    • Problems:
      • Microphone output is too noisy
      • Monitor filters and amplifies microphone output
      • Could not find final output
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Idea Four
    • Use a computer sound card
      • Some Filtering and Amplification done
        • WE CAN DETECT BREATHING!
      • Second Benefit
        • Eliminates the microcontroller
  • Gone from original plan to final plan
the microphone and sampling
The Microphone and Sampling
  • Basic microphone with cone-shaped addition
    • Dampens background noise
    • Collects more of the desired signal
  • Sampling
    • 8kHz, mono, 8-bit WAV files
    • Small file size
    • Nyquist Theorem limits sound content to 4kHz
breathing samples
Breathing Samples
  • Find frequency range by analysis on samples
  • Baby samples
    • Obtained at Provena Covenant NICU
    • Hard to hear breathing
  • Adult samples
    • Easier to hear breathing
analysis of breathing samples
Analysis of Breathing Samples
  • MATLAB
    • Short Time Fourier Transform (stft.m)
      • Outputs Fourier Transform of signal
      • Only use small portions of sample
    • Spectrogram (specgram.m)
      • Graph of Frequency vs. Time
      • 500-1000 Hz
      • Clearer than STFT
      • Use whole sample
filtering
Filtering
  • Butterworth Filters
    • MATLAB
      • Built-in functions generate filter coefficients
      • Background noise reduced
    • LABVIEW
      • Built-in function implements filter
      • Background noise reduced
      • Allows for further processing
filterbank
Filterbank
  • Reason
    • Some background noise always present
    • Want clearest output
  • 5 Bandpass filters
    • 500-1000 Hz
self calibration
Self Calibration
  • Determine Best Band
  • Generalized Signal to Noise Ratio
  • Highest SNR = Best Band
  • Constant, Autonomous Calibration
counting breaths
Counting Breaths
  • Recall, goal is to sound an alarm if 15 seconds passes without a breath
  • Counter
    • No breath = increment
    • Breath = Reset to zero
    • 8000 Samples/Sec x 15 Secs = 120000
    • Counter shows 120000…

A L A R M!

problems and possible solutions
Problems and Possible Solutions
  • Baby Samples
    • Breathing is not loud enough
      • Recommendations
        • Unidirectional Microphone
        • More Effective Pre-filtering – Reduce background noise
problems and possible solutions1
Problems and Possible Solutions
  • Using Real-time Data
    • Data acquisition + Data Processing = SLOW PERFORMANCE
      • Hard to actually see what is happening
      • Sampling Rate vs. Refresh Rate
    • Recommendations
      • External data acquistion
      • Feed data in as samples
looking ahead
Looking Ahead
  • Complete Heart Rate and Breathing Monitor
    • Need processing speed
    • Faint signal acquisition capability
  • Result
    • Reliable and inexpensive home monitoring system for infants
a special thanks to
A Special Thanks To:
  • Professor Swenson
  • Dr. Nestor Ramirez from Provena
  • Professor Jones
  • Professor Franke
  • Professor Hasegawa-Johnson
  • Professor Bernhard
  • Wojciech Magda and Shao Hsia
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