Jimmy Marsanico, Kubra Kuzu, Anthony Brown, Rahul Jain
Abstract
Technological advancements in the 21st Century are booming. It is believed that medical applications of technology are the future. When a patient dies at home or in a nursing home because of unknown heart conditions, it is asked, what else can be done? By focusing on medical monitoring solutions, not only will family members and loved ones of patients be at ease when away from a loved one in need of care, but the doctors will be able to monitor patients’ conditions from remote locations. Medical alarming systems will allow the monitoring of a patient and react knowing when a patient is in need of medical attention – often times, long before the patient knows he or she is in need of help. By developing a small, wireless monitoring system that is adaptable for any person to use, it is possible to create systems of communication for multiple patients and their doctors. These devices will be able to communicate wirelessly to nearby cell phones or computers in order to share the data in a way that makes it easy to access for both the patient and their doctor. The ideal system will have in place methods that will help to eliminate errors and expand efficiency of data transmission. Relaying this data back to a cell phone or base computer will allow for further processing of data, data storage, and the ability for data mining. Most importantly, the ability to deliver this data to a doctor’s smartphone for remote monitoring is a key component. When the data contains “life or death” information, speed and efficiency cannot be taken for granted. This technology is generalized enough have multiple applications. The monitoring of patients is useful for patients at home, patients in nursing home, and those in rehabilitation centers. The patient does not require full attention, as in an ICU, but is not stable enough to go completely unattended. This technology will change the medical field. The same way that Facebook took over social interaction in the 21st Century, medical wireless monitoring will change the way patients are cared for. The road to the preservation of human life in a world full of technology begins here. This paper will explain the steps on how we researched and applied this technology.
I. Determining Project Path: What is the Problem?
ECG (Electrocardiogram) is a signal that is used by medical professionals to determine what is wrong with the heart and the body. Based on medical usage of ECG, we found that the ECG is an extremely important vital signal that needs to be monitored for heart patients. Heart failure is common, but unrecognized and often misdiagnosed. It affects nearly 5 million Americans [7]. In 2008, over 616,000 Americans died of heart disease; almost 1 in every 4 deaths that year was due to heart disease [6]. We decided that if any vital signal was worth monitoring, ECG is a great start for this technology.
II. Background Information
ECG is a diagnostic precedure that measures electrical activity of the heart muscle over time. The electrical waves can be measured at selectively placed electrodes (electrical contacts) on the skin. Electrodes on different sides of the heart measure the activity of different parts of the heart muscle. An ECG displays the voltage between pairs of these electrodes, and the muscle activity that they measure, from different directions.
The ECG is recorded by placing an array of electrodes at specific locations on the body. Three types of ECG leads are recorded by the electrodes:
· Standard limb leads,
· Augmented limb leads
· Chest leads.
These electrode leads are then connected to a device that measures the potential differences between chosen electrodes and plots the characteristic tracings.
· Lead I: Positive electrode is on the left arm and negative electrode is on the right. It measures the potential difference across the chest between two arms.
· Lead II: Positive electrode is on the left leg, while the negative one is on the right arm.
· Lead III: Positive electrode is on the left leg and the negative one is on the left arm.
III. Proposed Process
For the application of ECG monitoring, we decided to use the Arduino board for comparison algorithms and for sending this information to a smart phone. The flow of logic for this project has been as such:
1. Take in an ECG signal from the body.
2. Pass the ECG signal through an amplification circuit.
3. Read amplified signal into Arduino board.
4. Run comparisons for max peak and frequency measurement.
5. Transmit data via Bluetooth to a smartphone.
6. Modify the application on the smartphone for optimization and expansion.
Each of these steps in the project has many sub-steps in them, including hardware, software, and communication capability.
IV. ECG Signal Acquisition
ECG signals consist of low amplitude voltages that are susceptible to a high level of noise. To acquire proper ECG signal, noise has to be suppressed and amplitude has to be enlarged. Suppression of noise can be made by using filters, while amplitude of signal can be enlarged by operational amplifiers. Heart signal frequency is generally bounded to a certain band that is between 0.05Hz and 2Hz, approximately 1 beat per second. Based on the Arduino hardware, the signal will require an offset as well to input an entirely positive signal for proper evaluation in software.
ECG Signal Analysis
Figure 1, above, shows a signal has five points of interest namely P,Q,R,S,T. These points are needed for ECG analysis and the analysis is as follows:
In Figure 1(Above):
-P is the open ventricle for atrium
-Q is the close action of the ventricle
-R is the push of blood by heart by the tricuspid valve
-S is the close of the valve
-T is the push of blood from the lungs to the heat i.e., blue blood
So the main question is: What causes irregular heartbeats and how do theylook?
- Spike at R.
- Depletion of P and Q which also leads to S spiking upward.
- S spikes downward, high blood pressure.
- Frequency is faster, tachycardia.
- Frequency is slower, bradycardia.
-Frequency is skipping, arrhythmia.
For other information the window of information needed is dependent on thesituation
- ICU - need every second, constant stream of information
- Rehabilitation, every 5 minutes the patient is checked, i.e., a 5 minutewindow.
For emergency, must know by first irregularity, do something by second.
The above information will be used for programming to evaluate the maximum as well as for determining the frequency and how often we should determine the frequency of the signal. In a real world application of a commercial product using the technology, the period in which the signal is tested and recorded will be programmable as per the doctor’s requests. There will also be certain security procedures that a doctor can set in order to allow patients different levels of control of the device; such as ability to change the period of testing, etc.
V. Amplifier
The major addition from last semester was to incorporate a frequency counter that would be able to tell the frequency of the signal read into the Arduino board. After some deliberation, we tested out a hypothesis of having two different inputs in the Arduino, one analog, one digital. The analog input was for the signal to give a maximum value, while the digital input was to enable us to use the frequency counter method [8] to run a frequency counter.
We then proceeded to run the frequency counter method [8] and try to understand how it works. After running several tests on the method, we came to the conclusion that the digital pin would need at least 5 Volts as a digital input in order to be able to accurately measure frequency. We also experimented with the analog section and concluded that we needed at least 1 Volt as an analog input to accurately measure maximum height of the ECG signal.
The ECG signal in itself has a voltage of 1 ~ 4 mV, thus amplification on the ECG signal will be needed to get the minimal voltage requirements of the digital and analog inputs. The amplifier and band pass filter we started working with was the one shown below in Figure2 (a):
We have to include an opto-coupler, to ensure that the patient does not have any current return to back to the electrodes on the skin, and a band-pass filter, so that we can remove the noise from our amplified signal.
After running multiple tests with an ECG generator, connected to the circuit in Figure 2(b), we were getting an amplification of approx. 700 times ~ 700 mV, however that is not enough for the required Arduino inputs, and we had to add an additional amplifier to get a higher amplification.
After some research we decided to add an amplifier to ensure that we were getting at least 5V into the digital pin of the Arduino. The amplifier that was added was the INA128 (Figure 3), after this amplification we had to shift the amplified ECG signal so that the smart phone would display the whole signal peak to peak and not a half signal. The amplification of our final amplifier design is in a range from 5000 times to 8000 times ~ 5V to 8V, giving us ample voltage of the digital signal required for the Arduino. The amplification range can be adjusted as desired by adjusting the variable resistor attached to the INA128.
VI. Reading the Signal into the Arduino Board
The Arduino development board is an open source kit that is used for many types of projects that include both analog and digital signal processing. Its popularity in the electronics field has provided much support for the hardware and its peripherals as well as for the software libraries. 99% of all Arduino support one may require can be found on the Arduino website, <www.arduino.cc>. Figure 5, on the left, shows the Arduino UNO, which is the most basic development board available. It is easy to use and fast to learn.
The UNO has a series of digital pins and analog pins on board. As explained later, in Section VII, the software will require a digital input for one section of the monitoring algorithm, but an analog input of the same signal for another segment of the algorithm. What we will be able to do is split the output from the amplifier circuit, ensuring there is enough current entering the board, and have one lead enter a digital pin and the other enter an analog pin. The UNO is capable of the A-D conversion, so having the analog signal from the amplifier enter the digital pin onboard will not be a problem. We will just keep in mind that we will use separate grounds for digital and analog pins [9].
VII. Logical Analysis and Software
The Arduino software will be in charge of analyzing the heartbeat signal. We will have three main software functions occurring on the Arduino: measuring the frequency of the heartbeat, monitoring the ‘R’ value of the ECG signal (which is the maximum amplitude of the signal, determined by the push of blood by the heart through the tricuspid valve), and finally recreating the patient’s signal on the smartphone.
The FreqMeasure.h library [8] will allow the Arduino to take in any signal into a digital pin and measure the frequency of a repetitious signal. We have the choice of taking a large average of values or grabbing an instantaneous frequency. As of now, we found that it is best to grab the most instantaneous value possible. Below in Figure 6, there is the method that we built from the FreqMeasure.h library.
This method will be put into one file combined with the ‘R’-level monitoring algorithm, which checks how healthy the functionality of the tricuspid valve is. Now this algorithm requires the analogRead() method, which returns an analog value. This value is what we will map backwards to a certain voltage level, which will be determined as healthy or unhealthy based on a general average, or programmed to a specific patient condition. The output of this algorithm [Good] or [Bad] can be directly printed to the patient’s phone as a signal with an alarm and it can also be sent via email or text message to a doctor’s device, once it is transmitted to the patient’s device.
VIII. Bluetooth and Transmission
Bluetooth technology gives us a way to connect one device to another device wirelessly, in close proximity. For our purposes on transmitting data by the use of a smartphone, Bluetooth works extremely well and is adaptable to those in any situation. It is no secret that the average American is likely to have a smartphone with Bluetooth capability in the 21st century. Utilizing a tool that most people carry with them every single day is what makes this technology scalable to the American market.
The Bluetooth Special Interest Group is the interest group that oversees the development of Bluetooth standards and all Bluetooth ™ technologies. They are a unification of telecommunications, computing, networking, industrial automation and automotive industries, and were founded in September of 1998. This Special Interest Group (SIG) includes companies such as Microsoft, IBM, Intel, Motorola, etc. The Bluetooth wireless technology is able to simplify and combine multiple forms of wireless communication into one single, complete, secure, low powered, low-cost, globally available radio frequency [4].
Bluetooth has worked on perfecting this technology by dealing with its faults: costs, transfer rates, and battery usage. Bluetooth is a short range wireless communication technology invented to easily allow users to create a personal area network, or in Bluetooth terminology, a pico-net. On the security aspect of Bluetooth technology, people have concern for security. This concern was made minimal because this technology will not automatically connect to Bluetooth enabled devices. If a user wants to pair with their device, they need a pairing key. If they do not want anyone to see the device, they can prevent their device from being visible to other Bluetooth devices by just switching the device to invisible. This ability and ease of use is marketed to allow anyone to be able to use this technology, but this push of functionality and usability can have detrimental effects on security [2].