An USB BASED ECG MONITORING DEVICE

Technical Field

The present invention relates to medical electronic instruments and more specifically, an USB based ECG monitoring device.

Background

Following abbreviations are defined herewith:

An electrocardiogram (ECG or EKG) is a text which produces graphic by an electrocardiograph. Electrocardiograph records the electrical activity of the heart over time shown in Figure 1. Heart muscles create electrical activity or waves when they contract and/or expand. These waves pass through the body and can be measured by electrodes (i.e. electrical contacts) attached to the skin. Electrodes on different sides of the heart measure the activity of different muscles. An ECG displays the voltage between pairs of electrodes and the muscle activity that they measure from different directions. This display indicates the overall rhythm of the heart and weaknesses in different muscles. It is currently the best way to measure and diagnose abnormal rhythms (arrhythmias) of the heart, particularly arrhythmias caused by damaged conductive tissue that carry electrical signals, or arrhythmias caused by salt and/or calcium levels that are either too high or too low.

There are over 350,000 cases of sudden cardiac death in the United States each year, of which over 20% involve people with no outward signs of serious heart disease. Further, another 300,000 patients experience heart-related arrhythmias each year. Researchers continue to study electrocardiogram (ECG) patterns that precede dangerous arrhythmias. As these patterns are found, devices are being created to monitor patient's hearts in order to detect the onset of dangerous arrhythmias and to hopefully correct them before they cause death.

Regularly tracking on changes in cardiac function is usually suggested for the elderly to maintain fitness. Generally in hospital, three-lead ECG measurement has been used to monitor cardiac function. Cardiac assessment in hospital requires significant time, and in case of delay in Cardiac assessment increases the risk to get affection and is also not convenient for the elderly.

Therefore, there is a need of a portable ECG monitoring device to meet the requirement of convenience and medical expertise. The portable device should be configured to record ECG data and transmit the same to a personal and hospital computer, if required.

Summary

The present invention discloses an USB based ECG monitoring device (USB-ECG) for monitoring of ECG and Heart Rate of a patient. The ECG monitoring device uses a plurality of sensors (electrodes) to monitor the ECG and measure the heart rate of the patient. In a preferred embodiment, three sensors (electrodes) are used to connect to right arm, left arm and right leg reference. The ECG signal (which is received) is in the range of 0.5 mV to 1.5 mV range. Strength of this low signal will be raised with a gain of 1000 by an Instrumentation amplifier and filtered for removing power line noise and other high frequency components. This filtered signal is fed to the ADC and the same is passed to QRS Discriminator for generating pulses corresponding to the heart beat. These pulses are fed to the Timer input of the Micro-Controller. These pulses are counted to measure the heart rate. The ECG Signal fed to ADC will be sampled and corresponding samples can be sent to the distant place via wireless transceiving unit. At the distant place, the signal is received and reconstructed on the GUI. The same data is fed to USB Port of a computer to which it is connected, and GUI is used to display the ECG Waveform and the corresponding Heart Rate.

The present invention discloses an USB based ECG monitoring device comprising:

a plurality of sensors for receiving an ECG signal;

a signal processing unit operatively coupled to said sensors for processing said
ECG signal;

a micro-controller operatively coupled to said signal processing unit; and

an USB module coupled to said micro-controller for providing an output signal of said micro-controller to an external unit through an USB port,

said USB module configured to provide power to said ECG monitoring device from said external unit.

The present invention further discloses a method for monitoring ECG comprising:

receiving an ECG signal from a plurality of sensors attached to a human body;

processing said ECG signal;

converting the processed ECG signal which is an analog signal, into a digital signal; and

providing said digital signal to an external unit and/ or remote unit for processing and displaying the ECG signal.

Brief Description of the Drawings

The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:

Figure 1 illustrates an ECG wave form.

Figure 2 illustrates a block diagram of an USB based ECG monitoring device according to an embodiment of the present invention.

Figure 3 illustrates a block diagram of an USB based ECG monitoring device according to another embodiment of the present invention.

Figure 4 illustrates an ECG Signal and its components.

Figure 5 illustrates an USB based ECG monitoring device according to a
preferred embodiment of the present invention.

Figure 6 illustrates a flow diagram of a method for monitoring ECG according to an embodiment of the present invention.

While the invention will be described in conjunction with the illustrated embodiment, it will be understood that it is not intended to limit the invention to such embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined.

Detailed Description

The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments. The present invention can be modified in various forms. Thus, the embodiments of the present invention are only provided to explain more clearly the present invention to the ordinarily skilled in the art of the present invention. In the accompanying drawings, like reference numerals are used to indicate like components.

Figure 2 illustrates a block diagram of an USB based ECG monitoring device 200 (USB-ECG) according to an embodiment of the present invention. The ECG monitoring device comprises a signal processing unit 201, a micro-controller 202 (MCU), an USB Module 203, and a wireless transceiving unit 204. The signal processing unit 201 receives a plurality of signals which are sensed by a plurality of sensors (electrodes). These signals are processed and then provided to the micro¬controller 202. The USB module 203 is connected to the micro-controller 202 for receiving an output signal of the micro-controller 202, and providing the same to an external unit through an USB port. Additionally, the USB module is configured for providing power to said ECG monitoring device from said external unit. The ECG device 200 further comprises a memory device (not shown in figure) for storing the information /data.

The USB based ECG monitoring device 200 monitors the ECG and measures the heart rate of a patient to assess the condition of patient / person heart. This data is sensed through the attached sensors (electrodes), which are then fed to a micro¬controller 202 for processing. After processing, the data is transmitted to an external unit such as PC, Computer, Computing device, Display device into which the USB-ECG unit is plugged in. The computer monitor displays the ECG wave form and the heart rate of a patient /person based on the data received at the USB port.

The wireless transceiving unit 204 is connected to the micro-controller 202 for transmitting and/or receiving data with at least one remote unit. The remote unit receives the transmitted data, processes the data as per the requirement of remote unit, and displays the ECG signal.

Figure 3 illustrates a block diagram of an USB based ECG monitoring device 300 (USB-ECG) according to another embodiment of the present invention. The signal processing unit 201 of an ECG monitoring device 300 comprises an instrumentation , amplifier 301, a band pass filter 302, a notch filter 303, a QRS Discriminator 304, and a Comparator 305.
The Instrumentation amplifier 301 is a closed-loop gain block. The amplifier 301 has a differential input and an output that is single-ended with respect to a reference terminal. The instrumentation amplifier amplifies the difference between two input signal voltages while rejecting any signals that are common to both inputs. Therefore, the instrumentation amplifier provides the very important function of extracting the small ECG Signal from the ECG electrodes (sensors). The gain of the instrumentation amplifier can be adjusted using the potentiometer.

The band pass filter 302 is provided for detecting the rhythm disturbances. Restricted bandwidth (0.05Hz to 40Hz) attenuates higher frequency noise caused by muscle contractions. This particular bandwidth is used for patient monitoring purpose.

The Notch Filter 303 of 50/60 Hz is provided in the signal processing unit 201 for rejecting the power line frequency. The filter 303 is having an important role because of the high gain of the Instrumentation amplifier 301. The notch filter 303 filters out the power line noise which is amplified and provided at the output terminal of the instrumentation amplifier 301.
The QRS Discriminator 304 extracts the QRS Signal (shown in Figure 4), which is centered at 17 Hz. The QRS Discriminator 304 has a band pass filter, which is centered at 17 Hz, for performing this operation. Hence the P and ST segments shown in Figure 4 will be eliminated with this particular filter.

The Comparator 305 receives the output of the QRS Discriminator 304 and generates a pulse for every QRS signal detected. These pulses have bi-polar voltage. So using a diode, the negative part of the pulses, generated from comparator, is eliminated. Hence the bi-polar natured pulses are converted to uni¬polar pulses. These pulses are fed to a timer input of the Micro-controller 202.

The Micro-controller 202 counts the number pulses appeared per minute and displays the heart rate on the display device (PC monitor). The Micro-controller 202 includes a wide range of peripherals from a simple low power comparator to high-performance data converters, interfaces and multiplier.

In one embodiment of the present invention, the Wireless transceiving unit 204 meets IEEE 802.15.4 standards and support the unique needs of low-cost, low-power wireless sensor networks. The transceiving unit 204 requires minimal power and provides reliable delivery of data between devices. The transceiving unit 204 operates within ISM (Industrial Scientific and Medical) 2.4 GHz frequency band. The indoor data transmission or reception range is up to 30 m, and outdoor line-of-sight is up to 100m. The transceiving unit 204 is connected to micro-controller via UART interface. All kind of data and commands are sent to the transceiving unit 204 via the UART interface. RF data rate is up to 250,000 bps and serial interface data rate is from 1200 - 115200 bps. The transceiving unit 204 uses ZigBee to send data from the ECG monitoring device (USB-ECG) to a distant PC. The data contains ECG waveform related digitized data, and heart rate. This data is sent via ZigBee with corresponding headers attached. At the distant computer, this data is received and reconstructed for displaying the ECG Waveform and heart rate.

In one embodiment, the transceiving unit 204 operates from 2.8 volts to 3.4 volts supply. Minimum input high level required is 0.7 times the Vdd applied (= 2.31volts as Vdd = 3.3 volts) and a maximum of Vdd applied. Active mode current is almost 50 mA and power-down current is less than 10uA.

ZigBee is the name of a specification for a suite of high-level communication protocols using small, low-power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs), such as wireless headphones connecting with cell phones via short-range radio. The technology is intended to be simpler and cheaper than other WPANs, such as Bluetooth. ZigBee is targeted at radio-frequency (RF) applications that require a low data rate, long battery life, and secure networking. ZigBee protocols are intended for use in embedded applications requiring low data rates and low power consumption.

The USB Module 203 connects the ECG monitoring device 300 to a computer for displaying the ECG wave form and the corresponding heart rate. In addition, the USB Module 203 provides power supply from a computer USB slot (to which it is connected) to the ECG monitoring device 300. The ECG monitoring device 200, 300 do not require external power for it's operation.

Figure 5 illustrates an USB based ECG monitoring device 500 according to a preferred embodiment of the present invention. The ECG monitoring device is connected to three sensors to monitor the ECG and measures the heart rate of a patient. These three sensors are connected to right arm, left arm and right leg reference points. The ECG signal obtained is in the range of 0.5-1.5 mV.

The strength of this low signal is raised with a gain of 1000 by an instrumentation amplifier and filtered to remove power line noise and other high frequency components. This filtered signal is fed to the analog to digital converter (ADC) and then passed to the QRS Discriminator for generating pulses corresponding to the patient's heart beat. These pulses are then fed to the timer input of the Micro-Controller. These pulses are counted to measure the patient's heart rate.

The ECG signal fed to ADC will be sampled and the corresponding samples are sent to a distant location via wireless transceiving unit where it is received and reconstructed on the graphical user interface (GUI). The same data is fed to the USB Port of the PC to which the ECG monitoring device is connected. The graphical user interface is used to display the ECG wave form and the corresponding heart rate. In a preferred embodiment, the wireless transceiving unit comprises a ZigBee Module.

Figure 6 illustrates a flow diagram of a method for monitoring ECG according to an embodiment of the present invention. The ECG signal is received by a plurality of sensors which are attached to a human body 601. The received ECG signal is processed by a signal processing unit 602. The processing of the ECG signal includes amplifying the ECG signal, filtering out the power line noise and other high frequency component, detecting the QRS signal; and generating pulses corresponding to the patient's heart beat. The processed ECG signal is in a form of analog signal which is then converted into a digital signal 603. Then the digital signal is provided to an external unit and/ or remote unit for processing and displaying the ECG signal 604.

The ECG monitoring device 200 (USB-ECG) has advantage of using minimum hardware requirements, such as ZigBee modules, and even enable a physician to monitor the ECG of a patient on a distant PC up to 70 meters away without any repeaters and if with repeaters, it can go up to many kilometers. Additionally, the device 200 do not require external power supply for it's operation. It draws the power from an external unit through an USB port.
Although the invention of device and method has been described in connection with the embodiment of the present invention illustrated in the accompanying drawings, it is not limited thereto, it will be apparent to those skilled in the art that various substitutions, modifications and changes may be made thereto without departing from the scope and spirit of the invention.

We claim:

1. An USB based ECG monitoring device comprising.

a plurality of sensors for receiving an ECG signal;

a signal processing unit operatively coupled to said sensors for processing said ECG signal;

a micro-controller operatively coupled to said signal processing unit;
and

an USB module coupled to said micro-controller for providing an output
signal of said micro-controller to an external unit through an USB port,
said USB module configured to provide power to said ECG monitoring device from said external unit.

2. The monitoring device as claimed in claim 1 comprising a wireless transceiving unit coupled to said micro-controller for transmitting and/or receiving data with at least one remote unit, said remote unit processes and displays the ECG signal.

3. The monitoring device as claimed in claim 1, wherein said plurality of sensors comprises three sensors, said sensors are connected to right arm, left arm, and right leg references to monitor the ECG and measures the heart rate of the patient.

4. The monitoring device as claimed in claim 1, wherein said signal processing unit comprises:

a first unit coupled to said sensors for amplifying the ECG signal and
filtering out the power line noise and other high frequency component;
and

a second unit coupled to said first unit for detecting the QRS signal and generating pulses corresponding to the patient's heart beat.

5. The monitoring device as claimed in claim 1, wherein said micro-controller
operatively coupled to said first unit of said signal processing unit for receiving
filtered signal at an ADC input port, and coupled to said second unit for receiving pulses corresponding to the heart beat at a timer input.

6. The monitoring device as claimed in claim 1, wherein said external unit is selected from a group comprises PC, Computer, Computing device, display device, which is being used for processing and displaying the ECG signal.

7. A method for monitoring ECG comprising:

receiving an ECG signal from a plurality of sensors attached to a human body;

processing said ECG signal;

converting the processed ECG signal which is an analog signal, into a digital signal; and

providing said digital signal to an external unit and/ or remote unit for processing and displaying the ECG signal.

8. The method as claimed in claim 7, wherein said processing of ECG signal comprises:

amplifying the ECG signal;

filtering out the power line noise and other high frequency component;

detecting the QRS signal; and

generating pulses corresponding to the patient's heart beat.

9. An USB based ECG monitoring device substantially as herein described with reference to the accompanying drawings.

10. A method for monitoring ECG substantially as herein described with reference to the accompanying drawings.