The National Heart, Lung, and Blood Institute states that “more than a million persons in the U.S. have a heart attack and about half (515,000) of them die in each year. About one-half of those who die do so within 1 hour of the start of symptoms and before reaching the hospital”. A heart attack happens to a person when the blood flow and oxygen supply to heart muscle is blocked, and it is mostly caused by the Coronary Artery Disease (CAD). CAD occurs when the arteries that supply blood to the heart muscle (coronary arteries) become hardened and narrowed. It often causes irregular heart beat or rhythm by blocking blood stream. The National Heart, Lung, and Blood Institute suggest that “everyone should know the warning signs of a heart attack and how to get emergency help”.
The symptoms of heart attack can be detected by observing electrocardiogram (ECG) waveform. An ECG is an electrical recording of the heart and is used in the investigation of heart disease. An electrical impulse initiates muscle contraction, which results in heart beating. The spacing between pulses provides a measure of the heart’s rhythm, whereas the height of the pulses is an indicator of pumping strength. By observing the ECG waveform, the heart condition of the patients can be explained by doctors.
The ECG Library shows many samples of abnormal ECG waveform, and they are mostly collected from aged people who are more than 55 years old. The senior citizens are more prone to have heart attack than young people. The Walking Stick with Heart Attack Detection is specially designed to help the senior citizens who need walking aids by walking sticks and have the most possibility of heart attack. The walking stick is used as detection unit and as the medium asking for medical help.
1.1 Overview of Design
The ECG circuitry unit on the wrist captures abnormal heart beat signal from the patient. The microcontroller on the stick runs a heart attack algorithm. Warning is given out to the person about his heart condition. The Bluetooth emergency calling system calls for medical help at the moment of heart attack. This project aims to shorten the time between the moment of heart attack and the arrival of medical personal. The warning before the emergency call will give the patient a chance to avoid heart attack.
Figure 1.1 Block Diagram of Walking Stick with Heart Attack Detection
Two biosensors worn on the user’s wrists send the real ECG signal to the analog ECG circuitry. The amplified and filtered analog output of the circuitry is converted from analog to digital signal and transmitted to the unit on the walking stick. The ECG circuitry unit, the A/D converter, and the transmitter are worn on one of the user’s wrists. The wireless connection between the unit on the wrist and the main unit on the walking stick gives the user more freedom to move by avoiding wire attachment between the wrist and the stick. The receiver on the stick receives the digital ECG signal, and the microcontroller runs a heart attack algorithm to detect possible heart attack symptoms. If any symptom of heart attack is detected, the risk level rises. When the risk level reaches up to the emergency mode, the Bluetooth module activates the user’s mobile phone to call 911 for medical help. Latest mobile phones include GPS function. Therefore, the GPS unit is eliminated from the previous project as the mobile phone’s GPS can locate the user.
For the design of the ECG circuitry and the ECG algorithm, the specifications of the previous project “Wireless Heart Attack Detector with GPS” were used.
The frequency range of ECG signal depends on the activity of individual. The typical range is approximately from 50 Hz to 70 Hz. To cover a wide range of frequencies for all scenarios, the band-pass filter of the ECG circuitry is designed to have a lower cutoff frequency of 0.5 Hz and an upper cutoff frequency of 150 Hz. The analog...
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