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

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

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

  2. 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

  3. 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

  4. What’s Out There Now? • Monitoring by Impedance Nemography • Breathing is measured by movement of electrodes • Unreliable and expensive

  5. 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

  6. 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

  7. 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?

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. Sample and STFT Output

  15. Spectrogram Output

  16. 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

  17. Filterbank • Reason • Some background noise always present • Want clearest output • 5 Bandpass filters • 500-1000 Hz

  18. Filterbank Output

  19. Self Calibration • Determine Best Band • Generalized Signal to Noise Ratio • Highest SNR = Best Band • Constant, Autonomous Calibration

  20. 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!

  21. Problems and Possible Solutions • Baby Samples • Breathing is not loud enough • Recommendations • Unidirectional Microphone • More Effective Pre-filtering – Reduce background noise

  22. 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

  23. Looking Ahead • Complete Heart Rate and Breathing Monitor • Need processing speed • Faint signal acquisition capability • Result • Reliable and inexpensive home monitoring system for infants

  24. 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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