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Today, I am writing an article on the design and construction of a heart attack detection and monitoring device. This article is a fraction of my post-graduate research work. I decided to share the outcome of this work with you so that you can be informed about the deadly heart condition called heart attack and possibly encourage you to have a heart test so that you can know the condition of your heart

The internal layout of the constructed device before putting it in a case

Let's get started

Introduction

The alarming rate at which people die of heart attack these days is of great concern to scientists and medical practitioners. The means of reducing this untimely death gave birth to this present work; the development of patient heart attack detection and monitoring device using heartbeat sensor. In October 2015, Dr. Kamar Adeleke confirmed Heart diseases to be the number one killer disease in Nigeria. Hannu Sorvoja considered Cardiovascular diseases as the number one of the leading causes of death. Globally, these heart-related diseases are responsible for the death of one-third of the world’s population and in Europe, they cause half of all deaths. These diseases can be divided into coronary, cerebral or peripheral artery diseases. (Hannu Sorvoja,2006)

Cardiovascular diseases are mainly caused by atherosclerosis. Atherosclerosis is a medical term used when the arterial compliance decreases tremendously which in turn resulted in increased arterial stiffness (van Popele et al. 2000 and 2001), which serve to increase the patient’s death risk (Mattace-Raso et al. 2006). Heart attack which is coronary artery disease is commonly caused by the effects of aging, the huge deposit of cholesterol and fatty substances in the arterial walls, emotional stress and effects of drug intake lead to involuntary contraction of the muscle (spasm) in blood vessel walls. As the spasm continues to build up, there will be a reduction in the blood flowing through the arteries, which also caused a reduction in the amount of oxygen reaching the heart muscle from oxygenated blood.

Also, the build-up of spasm causes all organs of the body that are deprived of oxygen and nutrient to die including the heart itself, because the heart also needs this oxygen and nutrients to survive. This eventually leads to a heart attack and could also result in permanent damage to the heart called Myocardial infarction, if proper medical attention is not given to the heart patient on time.

By National Heart Lung and Blood Institute (NIH) - Public Domain, large coronary artery with plaque buildup

The heartbeat rate detection and monitoring device built is designed to seek the attention of a doctor if a person is about to have a heart attack. How could this possible? This device is capable to detect the heartbeat rate level of a patient and if the heartbeat rate level falls out the normal heartbeat rate limit, usually (60 to 100 BPM), the device will send an alert as a text message to the doctor's registered phone number to inform the doctor or an emergency unit about the incidence for immediate response.

The system makes use of heart beat sensor (pulse sensor) to find out the current heart beat level and display it on the LCD screen. Heart attack detection using Heart Beat Sensor (Pulse Sensor) works on the principle and technique of Photoplethysmography (PPG). Photoplethysmography can be described as a simple and low-cost optical technique that can be used to detect changes in blood volume in the microvascular bed of tissue. This technique basically relies on the ability of red blood cells (haemoglobin) to absorb light, howbeit, an infrared light source is placed on one side of a finger to illuminate the finger, and a photodetector is placed on the other side of the finger to detect and measure small variations in transmitted light intensity as the haemoglobin absorbs light when blood is being pumped through the arterial walls to the finger tip. These variations in light intensity as detected by the photodetector correspond to how the heart beats.

Image taken while testing the device

METHODOLOGY

The device consists of eight stages namely; the power supply unit, the microcontroller unit, the detection unit, the monitoring unit, the voice/alarm unit, the display unit, data logger unit, and the pill schedule reminder unit. Electronic components used for this work includes Voltage Regulator, Atmega328 microcontroller, SD card shield V1.0, Easy Pulse V1.1 heartbeat sensor, LCD display, SIM808 GPRS/GSM Module, Resistors, Capacitor and Diodes.

Figure 1: Block diagram of heart attack detection and monitoring system

System design and implementation
This project is a system containing several parts which can be divided into two main units, the hardware, and the software units. For further simplification, each one of these units is classified into categories based on their functions.

The hardware Design

The hardware of this work is an integration of eight units: the power supply unit, the microcontroller unit, the detection unit, the monitoring unit, the voice/alarm unit, the display unit, data logger unit, and the pill schedule reminder unit. The Microcontroller Unit employs the function of Arduino UNO as the control unit for the system. It is a microcontroller board based on the ATmega328P datasheet. For this work, Arduino UNO embedded with GPS, GPRS, and SIM 808 (SIMDUINO) feature was used for design simplicity and better functioning system. SIMDUINO (ACM12425E) was powered by AC-to-DC, 2A power adaptor.

The display Unit is a 1602A LCD screen to output data from various modules on a screen. VSS is a power pin connected to the ground. VDD take 5 V is power. VL for LCD contrast adjustment, a 10 K variable resistor can be connected to adjust potentiometer contrast. RS, RW, D4, D5, D6 and D7 pins were connected to digital pins 3,4,17,16,15 and 5 respectively.

The detection and measurement of heart beat rate was achieved using a heart pulse sensor. Easy pulse sensor measures the real-time heartbeats and calculates BPM with the aid of algorithms implemented by Arduino. It is used for detecting the cardio-vascular pulse wave from a fingertip, illustrate the principle of photoplethysmography (PPG). Easy pulse sensor operates on +5V power supply. Two stages filtering and amplification was achieved using MCP6004 OP-Amp. The analog PPG output of the sensor was connected to the analog pin 0 of the Arduino board.

The monitoring of patient heartbeat rate was achieved using Elecrow Simduino (Model ACM12425E). The module is programmed to send a message in form of text to a registered phone number, preferably a doctors phone number or an emergency unit whenever the patient heartbeat is out of the normal healthy heart rate range (60BPM – 100BPM). A 2G Micro SIM card is required to use the module.

A Real Time Clock or RTC is a battery-powered clock that measures time even when there is no external power or the microcontroller is reprogrammed. An RTC displays clock and calendar with all timekeeping functions. In this project, a Real Time Clock, which displays accurate time and date along with an alarm feature has been designed using RTC DS1307. The RTC DS1307 has five pins: DS, SCL, SDA, VCC and GND pins. The SCL (Serial Clock), the SDA (Serial Data) pins are connected to analog pin 5 and 4 respectively. Both the SDA and SCL pins of RTC are pulled high using 10KΩ resistors. The communication between the microcontroller and RTC IC DS1307 is achieved through a serial I2C bidirectional bus.

SD card Data logging shield V1.0 was used with micro SD memory card to save the current heartbeat status of the patient as read by the heart pulse sensor. SD card Data logging shield V1.0 consists of the CS, MOSI, SCK, MISO VCC and the GND pins. The CS pin is connected to digital pin 10 of Arduino board, MOSI pin is connected to digital pin 11 of Arduino pin, SCK pin is connected to digital pin 13 of the Arduino, MISO pin was connected to digital pin 12 of the Arduino, the VC takes 3.3V and the GND was connected to the ground terminal if the Arduino board.

The alarm/ voice unit of the system works on both the external speaker and earpiece (headphone). Due to a special very high-speed PWM, Sound is output on digital pin 3 directly without further filtering and amplification. The unit is capable of producing the voice note of the current heart status of the patient as detected as measured by the heart pulse sensor. This feature was added to the benefit of a patient with sight defects, who can not see the readings displayed on the LCD screen. A 5V, 2A regulated power supply adaptor was used to power the Arduino Uno, the Easy pulse sensor and the LCD display, while the RTC module and the SD card shield were powered from the power output of the Arduino UNO board.

My Image taken while contructing the device

Software Implementation

The software implementation of this work was done in the Arduino IDE. The program (soft code) consists of a set of instructions to be executed one after the other (sequentially). Each function of the system is programmed in a void function ( ) with different function name so that each main functions could be called for any place within the programming environment. The functions are: detection and measurement of heartbeat rate in beat per minute (BPM), monitoring the hear-beat rate and sending the measured data to a doctor registered phone number once the measured data is out of range (60 – 100 BPM) for immediate response in case of emergency, to save the measured heartbeat rate in a SD card for future use, to program a RTC module to serve as pill reminder device and to include a talkie function to the system to enable the system talk to you, it also includes alarm unit for the pill reminder function.

The algorithm for measuring heart beat rate in beat per minute (BPM) is:

1. Initialize Arduino configurations.
2. Apply input signals to A1.
3. Read ADC samples.
4. Remove DC component.
5. Find the minima.
6. Scale data.
7. Find three peaks of heart pulse rate.
8. Compute pulse rate
9. Display pulse rate
10. Repeat from step 3.

Results and Discussion

Table 1: Table showing the heart beat rate(BPM) of both the conventional and the constructed detector

The Table 1 above shows the values of heartbeat rate per minute (BPM) as measured by the conventional detector and the constructed detector with corresponding percentage accuracy. Figure 2 shows the comparative line graph plot of the conventional detector and the constructed detector. It should be noted that the values of both detectors were taken in the morning, after observing ten-minute rest in bed. Sight differences were observed in the readings, thereby causing a slight deviation in accuracy when compared to the two detectors except in observation 8, where there was a significant difference.

The highest percentage accuracy observed was in observation 1 and 2 with 98.7% while the lower accuracy was observed in observation 8 with 71.2% accuracy. The significant difference observed in observation 8 was due to wrong body posture while taking the measurement (patient should be in a right sitting position and the hand on which the measurement is taken should be as stable as possible because wrong body posture affects the blood variation measurement within the blood tissue wall).

Figure 2: The comparative line graph plot of the constructed detector and the conventional detector

Conclusion

This work has developed a heart attack detection and monitoring device using heart beat sensor. The developed device provides a substitute for other imported heart beat monitoring devices since the result of this work shows a slight deviation when the conventional and constructed devices were compared, except in observation 8 where there was a significant difference, due to wrong body posture of the patient while taking the measurement. An Omron blood pressure monitor cost #25,000, while this locally developed device cost less than # 12,000, therefore, it is cheaper to patronize the constructed device.

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Design and Construction Implemented by
Olatunde Ibukun Daniel
E-mail: oluwabori4real4sure@gmail.com

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