ecg user manual for maxrefdes100 · 2020. 10. 19. · note: for the purpose of this user manual,...

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ECG User Manual for MAXREFDES100 APPLICATION NOTE 7214; Rev 0; 9/2020


Abstract This user guide introduces using the electrocardiogram (ECG) and R-to-R heart-rate functions of the MAXREFDES100 Health Sensor Platform. The ECG is available as a 1-lead measurement.

Introduction Electrocardiogram measurements provide a key biometric on the heart activity. Whether it is a patient in a clinic or hospital setting or an athlete training, monitoring the electrical activity of the heart yields valuable information on a person’s wellness. This user guide introduces the principles of measuring the ECG and illustrates how Maxim’s REFDES100# can be used to observe and record a subject’s ECG signal.

ECG Output An electrocardiogram (ECG or EKG) is the measurement and graphical representation, with respect to time, of the electrical signals associated with the heart muscles. All ECGs pick up heart signals through the electrodes connected externally to specific locations on the body and the signal in between each pair of electrodes shows a picture of the heart, or a channel. These channels are commonly referred to as “leads.” Depending on the application, the number of leads varies from 1 to 12. The heart is a muscular pump made up of four chambers. The two upper chambers are called the right and left atria, and the two lower chambers are called the right and left ventricles. A natural electrical system causes the heart muscle to contract and this pumps blood through the heart and the rest of the body. An ECG shows the heart’s electrical activity from the pumping as line tracings on a screen. The spikes and dips in the tracings are called waves; electrical events during a heartbeat is shown as a PQRST wave (see Figure 1).

Figure 1. PQRST waveform. Each letter in this waveform is indicative of a certain activity in the heart. Figure 2 depicts what action the heart takes to develop each part of the ECG wave. The p wave is the first short upward movement of the ECG tracing and indicates the atria are contracting, pumping blood into the ventricles. The QRS complex—normally beginning with a downward deflection (q), a larger upwards deflection (r), and then a downwards wave (s)—represents the ventricular depolarization and contraction. The PR interval indicates the transit time for the electrical signal to travel from


the sinus node to the ventricles. The t wave is normally an upwards waveform representing ventricular repolarization.

Figure 2. Different stages of PQRST waveform. The rate or rhythm of the PQRST waves gives an indication of what is going on in the human body (see Figure 3). The ECG readings differ based on the age (pediatric patient versus adult patient), genetic predisposition, or patients having heart diseases.

Figure 3. Sinus rhythm. A few examples of ECG readings can be seen in Figure 4.


Figure 4. Different ECG readings.

ECG Electrode Placement As mentioned earlier, ECGs can have a 1–12 lead system, and the number of leads is based on the number of electrodes, which can range from 2 to 10. Leads and electrodes sometimes get interchanged; however, they both have different connotations. An electrode is the physical “patch” that is placed on the body to collect the signal, while a lead is the potential signal that an electrode pair can produce by forming a channel. The placement of the electrodes is important to capture the proper signals from the heart. The basic placement is Einthoven’s triangle (Figure 5): right arm, left arm, and left leg (which produces a triangle). Leads I, II, and III, provides the information among each electrode.

Figure 5. Einthoven’s triangle. Only one lead can be measured at a time since there is no ability to measure all the three leads (I, II, III) simultaneously. Physical adjustments of electrode placements must be made as mentioned in the example below which is consistent with Figure 5.

For Lead I • ECGN: RA

• ECGP: LA

• VCM: LL (as a body bias)

For Lead II • ECGN: RA

• ECGP: LL


• VCM: LA (as a body bias)

For Lead III • ECGN: LA

• ECGP: LL

• VCM: RA (as a body bias)

However, standing in the manner (with arms stretched out and upright) is not practical so the electrodes can also be placed on the torso as seen in Figure 6 and later in Figure 15.

Figure 6. Practical electrode placement.


There are two main systems used for ECG leads color coding: the American Heart Association (AHA) and the International Electrotechnical Commission (IEC). The comparison between the two systems can be seen in Table 1.

Table 1. Inscription and Color Differences between the Two Coding Systems

LOCATION AMERICAN HEART

ASSOCIATION (AHA) INTERNATIONAL ELECTROTECHNICAL

COMMISSION (IEC) INSCRIPTION COLOR INSCRIPTION COLOR

Right arm RA White R Red Left arm LA Black L Yellow Left leg LL Red F Green

Note: For the purpose of this user manual, the AHA coding system is used. See Table 1 if the IEC coding system is desired.

Hardware Setup Getting started with the ECG portion of the AHA system requires some preparation. There are different ways to connect the wires to the through holes. This user manual explains two separate methods, but the second method is used in the demonstration.

Method #1

Materials • ECG cables *

• MAXREFDES100# *

• Wire cutters/strippers

• Solder

• Solder iron

*Included in the EV Kit

Procedure

1. Using a wire cutter, snip off the connector end and strip a quarter inch of the rubber (Figure 7).


Figure 7. ECG wires.

2. Paying attention to the color of the electrode connector, solder the stripped end to the respective points on the health sensor platform (HSP) as shown in Figure 8.

Figure 8. ECG wire connection points on the board.


Method #2

Materials • Wires (red, black, white)

• Heat shrink tube ((red, black, white)

• 0.2in-spaced header pin (set of 3)

• Wire strippers

• Solder

• Soldering iron

• MAXREFDES100# *

*Included in the EV Kit

Procedure

1. Cut the red, black, and white wires into 3in and strip about an eighth of an inch off each end.

2. Solder one end of each color to the shorter end of the header pin (order: black, red, white).

3. Cover this connection with heat shrink tubing.

4. Solder each wire to the designated through hole. The final assembly should resemble Figure 9.

Figure 9. Alternative ECG wire connection points on the board.


Graphical User Interface This is the quick start setup of each of the tabs used for the ECG. For further description of how each of the different settings will affect the result, refer to the MAX30003 data sheet. The three tabs used for the ECG, other than the Home tab, are ECG Channel, ECG MUX, and Plots.

Home Tab The Home tab sheet (Figure 10) displays the block diagram of the HSP hardware. It also provides quick links to navigate to other tabs. The red block around the MAX30003 has quick links to the ECG Channel and ECG MUX tabs for modification of specific settings. The red block on the right around “ECG” goes straight to the Plots tab and configures all settings to their defaults for an ECG measurement.

Figure 10. Home tab sheet of MAXREFDES100 health sensor platform.

ECG Channel Tab The ECG Channel tab (Figure 11) controls the MAX30003/MAX30004 ECG channel and R-to-R settings.


Figure 11. ECG channel tab of MAXREFDES100 health sensor platform.

ECG MUX Tab The ECG MUX tab (Figure 12) controls the MAX30003/MAX30004 input multiplexers’ settings. A typical setting follows: The red boxes are the software graphical user interface (GUI’s) interpretation of what the on-chip R-to-R hardware is doing; by modeling the hardware in software, this acts as an example of the likely peaks that the R-to-R (Pan-Tompkins-based) algorithm is locking onto. It is not an exact callout of the specific analog-to-digital converter (ADC) samples that are being used by the on-chip R-to-R algorithm.


Figure 12. ECG MUX tab of MAXREFDES100 health sensor platform. Note: Under the Channel/Plot Enable at the bottom of the tab, “ECG” and “R-to-R” must be enabled before enabling lead bias.


Plots Tab The Plots tab (Figure 13) displays MAX30003/MAX30004 ECG measurement values.

Figure 13. Plots tab of MAXREFDES100 health sensor platform.

Taking Measurements

Chest Measurements—With Laptop and GUI

Materials • MAXREFDES100#* with ECG and cables*

• ECG electrodes**

• PC with working GUI

* Included in the EV Kit ** Electrodes used in the demo are 3M Red Dot (2570-5/2570-3) (Figure 14)


Figure 14. Red dot electrodes.

Procedure

1. Disconnect other devices from the laptop (e.g., monitors and projectors) as well as the charging cable to reduce interference.

2. Move the board and ECG cables away from the sources of electrical noise and closer to the body where the electrodes are placed.*

3. Place the electrodes on the skin based on Figure 15.**

4. Connect HSP to the laptop as shown in the HSP Quick Start Guide. https://www.maximintegrated.com/en/design/reference-design-center/system-board/6312.html/tb_tab1

5. Change the GUI to the desired settings or click the ECG quick start link on the Home tab to collect the data using the default settings.

6. Go to the Plots tab and press the Start Monitor button located at the lower right of the tab. It is important to remain still as motion will affect the ECG reading.

7. Collect the data.

8. To look at another tab, press the Stop Monitor button to proceed.

Figure 15. Electrode placement.

https://www.maximintegrated.com/en/design/reference-design-center/system-board/6312.html/tb_tab1https://www.maximintegrated.com/en/design/reference-design-center/system-board/6312.html/tb_tab1


* Long, unshielded ECG cables are susceptible to picking up noise, so using short and/or twisted ECG cables and keeping them close to the body where the electrodes are reduces coupled noise. ** This system is a Lead II of the Einthoven's triangle as shown above which allows for the strongest signal capture from the heart. The RA and LL acts as the main electrodes for the ECG and the LA acts as the body bias and reduces coupled noise. Safety Note: When streaming data to the GUI using the USB-C cable, use a laptop running from battery power to eliminate the noise from the power supply and avoid having a connection from wall power to the patient. Isolation is not built into the HSP. Ensure patient safety is followed. Look through the IEC60601-1 patient safety guidelines and ensure that minimum patient safety resistors are in place.

Wrist Measurements—With Laptop and GUI

Materials • MAXREFDES100#* with ECG cables*

• ECG electrodes**

• PC with working GUI

* Included in the EV Kit ** Electrodes used in the demo are 3M Red Dot (2570-5/2570-3)

Procedure

1. Disconnect the other devices from the laptop (e.g., monitors and projectors) as well as the charging cable to reduce interference.

2. Move the board and ECG cables away from the sources of electrical noise and closer to the body where the electrodes are placed.*

3. Place the electrodes on the skin based on Figure 16.**

4. Connect HSP to the laptop as shown in the HSP Quick Start Guide. Change the GUI to the desired settings or click the ECG quick start link on the Home tab to collect the data using the default settings. Go to the Plots tab and press the Start Monitor button located at the lower right of the tab. It is important to remain still as motion will affect the ECG reading.

5. Collect the data.

6. To look at another tab, press the Stop Monitor button to proceed.


Figure 16. Electrode placement on the wrist.

* Long, unshielded ECG cables are susceptible to picking up noise, so using short and/or twisted ECG cables and keeping them close to the body where the electrodes are reduces coupled noise. ** This system is a Lead II of the Einthoven's triangle as shown above which allows for the strongest signal capture from the heart. The RA and LL acts as the main electrodes for the ECG and the LA acts as the body bias and reduces coupled noise.

Safety Note:

When streaming data to the GUI using the USB-C cable, use a laptop running from battery power to eliminate the noise from the power supply and to avoid having a connection from wall power to the patient. Isolation is not built into the HSP. Ensure the patient safety is followed. Look through the IEC60601-1 patient safety guidelines and ensure that minimum patient safety resistors are in place.


Revision History REVISION NUMBER

REVISION DATE DESCRIPTION

PAGES CHANGED

0 09/20 Initial release —

©2019 by Maxim Integrated Products, Inc. All rights reserved. Information in this publication concerning the devices, applications, or technology described is intended to suggest possible uses and may be superseded. MAXIM INTEGRATED PRODUCTS, INC. DOES NOT ASSUME LIABILITY FOR OR PROVIDE A REPRESENTATION OF ACCURACY OF THE INFORMATION, DEVICES, OR TECHNOLOGY DESCRIBED IN THIS DOCUMENT. MAXIM ALSO DOES NOT ASSUME LIABILITY FOR INTELLECTUAL PROPERTY INFRINGEMENT RELATED IN ANY MANNER TO USE OF INFORMATION, DEVICES, OR TECHNOLOGY DESCRIBED HEREIN OR OTHERWISE. The information contained within this document has been verified according to the general principles of electrical and mechanical engineering or registered trademarks of Maxim Integrated Products, Inc. All other product or service names are the property of their respective owners.

ecg user manual for maxrefdes100 · 2020. 10. 19. · note: for the purpose of this user manual,...

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