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Vital Signs Monitor UConn BME 4900

Vital Signs Monitor UConn BME 4900. Vital Signs Monitor. Purpose As the population ages, many people are required by their doctors to take vital signs on a daily basis. Developed for the average person to use at home. Vital signs transmitted to a computer and ultimately to a doctor.

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Vital Signs Monitor UConn BME 4900

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  1. Vital Signs MonitorUConn BME 4900

  2. Vital Signs Monitor • Purpose • As the population ages, many people are required by their doctors to take vital signs on a daily basis. • Developed for the average person to use at home. • Vital signs transmitted to a computer and ultimately to a doctor.

  3. Measurements • What can it measure? • Electrocardiogram (ECG) • Three leads (Right arm, left arm, right leg)

  4. What is an ECG? • Records a time waveform of heart electrical activity. • Used to diagnose heart problems • Arrhythmia • Myocardial infarction • Conduction blocks (bundle branch block)

  5. ECG Trace

  6. Cardiac Electrical Activity

  7. The ECG Waveform

  8. Measuring Electrical Activity • 3 leads • 2 arm • 1 leg • As cardiac muscle depolarizes it creates a potential on the skin • Potential measured as a vector • Difference between right and left electrode measured with a differential amplifier.

  9. Measuring Electrical Activity • Circuit consists of: • 3 op amp differential amplifier • Low pass filter (Cutoff: 0.05 Hz) • High pass filter (Cutoff: 160 Hz) • Gain Amplifier

  10. Differential Amplifier Feedback Amplifier Buffer Differential Amplifier • What does the buffer do? • Provides a high input impedance which means low current flow • What is the purpose of C2 and C3? • Remove DC offset • Offset would be amplified by 1000x • 10 mV at 1000x gain = ~10V

  11. Differential Amplifier • V1 & V2 are in the microvolt range • We need it to be in the milivolt range so Rf/R1 is set to ~1,000

  12. 1st Order LPF • The ECG is known to be a low frequency signal • Usually less than 100Hz • A LPF can be used to remove the high frequency noise in the signal

  13. High Pass Filter • ECG frequency range ~0.05 Hz – 150 Hz • Why do we need to eliminate frequencies <0.05 Hz? • Avoid distortion of the ST wave

  14. Microprocessor • Provides Analog to Digital (A/D) conversion • Waveform y(t) sampled at a fixed rate Δt • Voltage read every Δt and converted to a number • If resolution is 8 bits • Gives us 28 = 256 counts over 5V range • ~19.5 mV per count

  15. Patient Isolation • Bluetooth is wireless technology • Bluetooth provides separation of the patient from the equipment and line source • Very important to protect patient from electrical shock

  16. Labview Software

  17. Labview Requirements • Receive serial data from bluetooth • Display raw and filtered EKG • Calculate heart rate

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