1. Senior Capstone Design Project Real-Time Electrocardiogram Spectral Analyzer Ryan Carnathan, Keith Berry, Mark Stadick, & Greg Michaelson Electrical & Computer Engineering

2. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

3. Requirements Apply knowledge Solve Real World Problems Work in Multidisciplinary Teams To become actively involved in a company or community organization.

4. Purpose Used in conjunction with the HP Merlin bedside monitor Real-time spectral analysis of the beat-to- beat variability Assess the potential for: –Improved bedside clinical monitoring –Diagnostic and predictive information

5. Function Graphical interface for the display and analysis of: –ECG Waveforms –QRS Complex Detection –Heart Rate Variability (HRV) Spectrogram These functions are performed and displayed in real-time.

6. Implementation Hardware QRS Detection Spectral Analysis Integration and User Interface

7. Definition of terms Electrocardiogram (ECG) Heart Rate Variability (HRV) QRS Complex RR v.s. NN The ECG Waveform The QRS Complex

8. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

9. Hardware Data Acquisition Card (DAQ) Laptop Computer Accessories

10. Data Acquisition Card Capabilities –Sample Rate 500 kS/s –Number of Channels 8 Differential 16 Single Ended –Gains 0.5, 1, 2, 5, 10, 20, 50, 100 –Voltage Levels ±10 V - ±50 mV Configuration –Sample Rate 1 kS/s –Number of Channels 1 Differential –Gain Setting 1 –Voltage Levels ±5 V

11. Laptop Computer CPU –Intel 600 MHz Pentium –256 k Level 2 Cache Storage –20 GB Hard Drive –3 ½ inch Floppy Drive Memory –512 MB of Ram Peripherals –Infrared Transfer –10/100 Network Card –56k Modem –(2) PCMCIA Slots 1 Taken by DAQ Operating System –Windows 2000 SP 1

12. Laptop Configuration CPU –600 MHz –500 MHz (Battery) Hard Drive –15.4 GB Free Ram Used –128 MB (System) –384 MB Available DAQ Input –1 Differential Channel –1 kHz Sample Rate –BNC Connection

13. Accessory Box Component Box Connector Block BNC Connection Ribbon Cable Strain Relief Device

14. Connections Merlin To DAQ –6.35 mm Audio Cable To BNC DAQ to Laptop –68 Pin Ribbon Cable (0.2 M)

15. Software Integration Program Functions –Initialize DAQ –Start Acquisition –Check Buffer –Transfer Buffer –Stop Acquisition Software –LabWindows CVI –MatLab 6.0

16. Acquisition Sample

17. Battery Efficiency CPU –Voltage = 1.35V (Full Power) Average Power < 2.0 Watts – Voltage = 1.1V (Battery) Average Power < 1.0 Watts Battery Life –3:15 per Battery 2 Batteries Possible DAQ Requirements –±5 VDC (±5%) 280 mA typ 400 mA max 70 mA unused

18. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

19. QRS Detection Overview QRS detection algorithm Current Status Future work Summary

20. QRS Detector Algorithm Block Diagram Remove OffsetFilterClip QRS Peak Detection Peak Acceptance/ Rejection Output QRS p-p Interval

21. QRS Detector Algorithm cont. ECG Input Data Remove Offset Filter Clip QRS Peak Detection Output QRS N-N Interval

22. QRS Detector Sample Output

23. Current Status Operational –Remove d.c. offset –Clip below amplitude threshold –Detect QRS complexes (clean signals only) Pending –Integration with graphical user interface –Digital Filter –QRS Accept/Reject function

24. Future Work 1st Priority –Integration with graphical user interface –Digital Filter –QRS Accept/Reject function –Final report outline –Testing and debugging

25. Future Work Continued 2nd Priority –Adaptive amplitude threshold function –Final report draft –Speed and performance improvements 3rd Priority –Final report –Final presentation

26. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

27. Heart Rate Variability (HRV) –Inter Beat Intervals (IBI) variation in the time intervals between beats assumes irregular beats have been removed normal to normal (NN) beats –Instantaneous Heart Rate (IHR) variation in consecutive instantaneous heart rates inverse of IBI Spectral Analysis

28. Power Spectral Density (PSD) –Distribution of Variance Over Frequency Three Operations –Resample –Filter –Generate Spectrogram Fast Fourier Transform (FFT) Transforms Time Signal to Frequency Spectral Analysis

29. Resample Filter FFT QRS Detector GUI Plot Block Diagram

30. Elapsed Time vs Number of Heart Beats QRS Output

31. Re-Interpreted Data From QRS Detector –NN Intervals –Indexed by Heart Beats NN Intervals

32. Interpolate –Generate Continuous Curve –Passes Through Existing Points Sample New Series –Constant Time Period –Required for Fast Fourier Transform (FFT) –NN Intervals vs Time Resampling Overview

33. Resampling –Input Signal from QRS Detector: –Resampled Signal:

34. Filtering Spikes in Signal –Missed Beats by QRS Detector –Distort Valid Data Filter –Flattens Large Excursions –Modifies Only Large Outlying Data Points

35. Filtering –Resampled Signal: –Filtered Signal:

36. Estimating Spectral Power –Remove Mean Value –Perform FFT –Power Calculation - |FFT| 2 Spectrogram Algorithm

37. PSD vs Time Spectrogram Example

38. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

39. Features Implemented –Plots ECG –User Controls Start/Stop Window Size Scrolling –Modes Historical Real Time Planned –Plots Beat to Beat Spectrogram Scaleogram –User Controls Graph Selection Notes

40. Process Budget Limits –Data Acquisition 10-15% of CPU Little Memory –Beat Detection 5-10% of CPU Lots of Memory –Spectrogram Calculation 30% of CPU

41. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration

42. Completed Hardware –Specified Needs –Purchased / Acquired –Built –Software Completed –Tested on Merlin GUI –2 Plots –Scrolling –Integration of Hardware –Real-time ECG Display –Historical Mode QRS Detector –Literature Review –Scaling –Clipping –Beat Detection Spectrogram –Resampling –Median Filter –Spectral Estimation

43. Remaining Tasks GUI –Spectrogram Integration –QRS Detector Integration –User Notepad QRS Detector –Filtering –Ectopic Beat Rejection Spectral Analysis –Filter Refinement –Higher Resolution Spectrogram Plot

44. Presentation Overview Introduction Hardware QRS Detector Spectral Analysis User Interface Summary and Conclusion Demonstration