1. Enhancing the Capabilities of a Wireless Holter Monitor Senan Garry 4 th ECE

2. Presentation Topics  Background Holter Monitor and ECG waves  Project Aims  ECG Sensor  Platform  Progress  Future Work

3. Holter Monitor  The Holter monitor records electrical signals from the heart via a series of electrodes attached to the chest.  Responsible for keeping a log of the heart's electrical activity throughout the recording period (usually 24 or 48 hr period) with a sampling frequency of between 500Hz and 1kHz  It is also useful in the fact that the patient can conduct their normal activities while wearing the device.

4. ECG Waves  The Electrocardiograph (ECG) signal is an electrical signal generated by the heart’s beating, which can be used as a diagnostic tool for examining some of the functions of the heart.  The electrocardiogram or ECG is today used worldwide as a relatively simple way of diagnosing heart conditions.  It has a principal measurement range of 0.5 to 4 mV and signal frequency range of 0.01 to 250 Hz.

5. Uses for ECG  assess your heart rhythm  diagnose poor blood flow to the heart muscle (ischemia)  diagnose a heart attack  diagnose abnormalities of your heart, such as:  heart chamber enlargement  abnormal electrical conduction

6. Project Aims  Integration of an LCD into the monitor to provide a display of ECG and status of device  Integration of GPRS functionality to provide an alternate communication mechanism when out of WLAN coverage,  Implementation of accurate ECG sampling at 500 Hz by altering Linux kernel,  Development of a voice recording mechanism onto the monitor based on a button push with download of recorded speech to system back-end.

7. Project Aims  Development of analogue circuitry to implement ECG sensor and amplification circuitry,  Basic ECG analysis software for back-end system (e.g. determination of heart rate and associated statistics)  Enhanced ECG analysis software for ECG anomaly detection

8. Design and implementation of ECG sensor and amplification software  Amplify the ECG waves measured  Filter these to filter out undesirable low and high frequency signals generated by noise and muscle movement before sending onto ADC ELECTRODESELECTRODES AMP FILTER ADC GUMSTIXGUMSTIX

9. Amplification  An ECG signal can vary in magnitude from patient to patient and can typically be in the range of 80-2OOOpV. This will require the signal to be amplified several hundred times before it is sampled.  The small voltage of the ECG also makes it vulnerable to many types of noise.  Since the voltages and currents from the electrodes are small in magnitude the amplifier input impedance must be very high. This requires the use of instrumentation amplifiers  AD620 (low noise, low input bias current and low power )

10. Filtering  ECG signals may be corrupted by various kinds of noise  The typical heart beat signal is between 0.05Hz and 60Hz therefore I decided I would keep it simple at first and filter out signals:  Less than 0.05 Hz and Greater than 60 Hz  If need s be further filters can be added onto the circuit  The OP97 is used in the right-leg common-mode feedback circuit applies an inverted version of the common-mode interference to the subject’s right leg, with the aim of canceling the interference.

11. ECG Sensor

12. Electrode placement:  Eindhoven’s triangle (most commonly used electrode placement scheme)  The differential potential is measured between: right and left arm,right arm and the left leg,left arm and left leg.  These part s of the body are used as they create the least amount of movement when a patient is moving

13. GUMSTIX  Decided on the Verdex XM4 as the platform to be used: GPRS ( GPS expansion board + GPRS antenna), LCD ready ( also GPRS ready), Processor: Marvell® PXA270 with XScale™ Speed: 400MHz Memory: 64MB RAM 16MB Flash Features: USB host signals CCD camera signals Connections: 60-pin Hirose I/O connector 120-pin MOLEX connector 24-pin flex ribbon Size: 80mm x 20mm

14. Progress To Date  ECG Sensor built but having difficulty with the circuitry (I think that the problem lie s in the filtering process as I cannot seem to display a clear ECG wave.)  Gained familiarization with the operation of the Gumstix platform and the Linux Kernel through tutorials and by compiling a new kernel and working my way through directories etc.

15. Future Work  Audio recording functionality  Alteration of kernel to support 500 Hz sampling  Basic LCD functionality + GPRS  ECG analysis software for ECG anomaly detection

16. ANY QUESTIONS ?????