2. Vital Signs Monitor UConn BME 4900

3. 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.

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

5. 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)

6. ECG Trace

7. Cardiac Electrical Activity

8. The ECG Waveform

9. 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.

10. 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

11. 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 Feedback Amplifier Buffer Differential Amplifier

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

13. 1 st 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

14. 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

15. 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 2 8 = 256 counts over 5V range ~19.5 mV per count

16. 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

17. Labview Software

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