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Background Information
According to the American Heart Association, each year:
785,000 Americans will have a new coronary attack470,000 will have a recurrent attack195,000 silent myocardial infarctions
Every 25 seconds someone will have a coronary event
Every 60 seconds someone will die of one
Background Information
Quick response time is crucial to surviving a heart attack because:
Cardiac arrest normally occurs within the first 2 hours of the heart attack
If victim is not treated within the first 2 hours, permanent heart damage can occur
Also, many infarctions can occur without the victim knowing
Specifications
Comfortable enough for around-the-house use
Quality signal and heart attack detectionMinimize errorLow noiseSample rate high enoughEfficient algorithm
Signal processing time frame
Heart sensors
Kendall Q-Trace 5400 Resting ECG Electrode
Silver/Silver Chloride (Ag/AgCl) sensing system
Pre-equipped with conductive adhesive hydrogel
Low impedance for a clearer signal
Project Break Down: 2 parts
1. Analog Circuit
Developing, constructing, and testing the following: Instrumentation
Amplifier Input Driver Optocoupler Output Driver High Pass Filter Low Pass Filter Output gain stage
2. Algorithm
Research how a heart attack affects an ECG waveform
Develop an algorithm to detect the occurrence of a heart attack
Translate the algorithm into MATLAB code for testing
Analog Circuit: Main Components
Instrumentation Amp AD620 chip Gain = 11 V/V
Output Gain Stage LM248 quad op-amp chip Non-inverting amp Gain = 100 V/V
High Pass Filter LM248 quad op-amp
chip Cutoff frequency: 0.05
Hz
Low Pass Filter LM248 quad op-amp
chip Cutoff frequency: 160 Hz
Common Heart Signal
Typical time spans:
PR interval: 120-200 ms
PR segment: 50-120 ms
QRS complex: 80-120 ms
ST segment: 80-120 ms
QT interval: 300-430 ms
Heart Attack Algorithm:ST Elevation
Most common and most damaging form of a heart attack
Requires immediate treatment
Heart Attack Algorithm Necessities
1. Establish a baseline (average of all samples in the PQRST waveform)
2. Detect QRS peak
3. Make sure the signal returns to the baseline directly after the peak within approximately 100 ms (width of ST segment)
4. If signal does not return to the baseline within 100 ms of QRS complex, alert the victim and dial 911
Possible Problems
Muscle activity
Extra common mode noise
Solution: Better amplifiers with higher CMRR
Use of Right Leg Driver
Power-line noise
Solution: notch filter at 60 Hz
Sources Kuangwei Hwang, Diane Limsui, Lianhan Zhao, “Wireless Heart Detector
with GPS”, Fall 2004, University of Illinois at Urbana-Champaign.
T. Buma, class notes for ECE 386, Department of Electrical Engineering, Union College, Winter 2012
ABC News, “What does an EKG show during a heart attack?” http://abcnews.go.com/Health/HeartDiseaseScreening/story?id=4223255#.T0MFeCNWq3w
MedicineNet.com, “Electrocardiogram (ECG or EKG)” http://www.medicinenet.com/electrocardiogram_ecg_or_ekg/article.htm
R. Spengler, “How does my doctor interpret my EKG,” 2002, http://yalenewhavenhealth.org/library/healthguide/en-us/support/topic.asp?hwid=tu6258abc.html
Vernier.com, “SensorDAQ”, http://www.vernier.com/products/interfaces/sdaq/
Helen Kim, Choon Yik Lee, “Walking Stick with Heart Attack Detection”, Spring 2005, University of Illinois at Urbana-Champaign.