What is an Electrocardiogram (ECG) Signal?
What is the ANSI/AAMI EC13 Standard?
The EC13 standard establishes minimum safety and performance requirements for electrocardiograph (ECG) heart rate and waveform monitors that are intended for use under the operating conditions specified in this standard. The standard covers:
- Heart rate indication via noninvasive ECG sensing from the patients body
- Amplification and transmition of signals to display the heart rate and/or ECG waveform
- Alarms, based on adjustable alarm criteria, upon the sustained occurrence of the following rate dependent phenomena: cardiac standstill, bradycardia, and/or tachycardia.
FDA Guidance for 21 CFR 870.2300, Cardiac Monitor
The US FDA Guidance Documents web site offers information to assist in the preparation of premarket notification (510k) applications for devices regulated under: CFR Section: 21 CFR §870.2300, Cardiac Monitor (including cardiotachometer and rate alarm). It is recommended by the FDA that substantial equivalence be demonstrated by showing conformance of a cardiac monitor to the ANSI/AAMI EC13 standard.
Performance Testing to ANSI/AAMI EC13 Standard
As noted in the FDA guidelines, to show substantial equivalence and conformance to the EC13 standard, a manufacturer should list each of the requirements of the standard and describe how the device conforms to each requirement. For every requirement, test data and analysis documentation should be provided and clearly identified. See the Data and Results section of "Suggested Format for Test Reports" on the FDA website.
Medical device corporations often exert many hours manually documenting test methods and results to the EC13 guidelines. In addition, many hours of an engineer’s time is often spent researching how to generate the device’s ECG input test signals as well as managing the large scale of test scripts. NI LabVIEW and NI Requirements Gateway can completely automate EC13 testing and documentation. LabVIEW is used to generate ECG signals that satisfy the waveform requirements for ANSI/AAMI EC13 and NI Requirements Gateway helps set up a standard and efficient verification process to reduce manual processes and increase quality.
Figure 1. Automating requirement traceability and documentation reporting
2. Generating Biosignals in LabVIEW
You will need to have the following applications in evaluation or full license form installed on your computer to use the example attachments:
- NI LabVIEW 2010 Full or Professional Development System or later
- NI LabVIEW Biomedical Startup Kit 3.0
- NI DAQmx 8.8 or later
- NI Requirements Gateway 1.1 or later
NI data acquisition hardware transforms ECG signals generating by LabVIEW into real voltage outputs and can also acquire analog signals for display in LabVIEW.
Download the LabVIEW Sample Code & Documentation
The library includes signal generation functions specifically for ECG and related waveforms, which are defined in standard ANSI/AAMI EC13 for cardiac monitors/heart rate meters/alarms. The generated waveforms used for testing are specifically defined in standards (ANSI/AAMI EC13, for cardiac monitors/heart rate meters/alarms).
NI Requirements Gateway traceability documentation is included for explicit traceability of information documents required by the EC13 standard. These imported documents include test requirements, test methods and test results. The NI Requirements Gateway tool helps set up a standard and efficient verification process to reduce manual processes and increase quality.
PhysioBank Signal Generation
Open the LabVIEW project For_LabVIEW_Tests_REQ.lvproj to see a list of VIs that can generate synthetic biosignals according to the ANSI/AAMI EC13 standard. You can find these VIs by opening the file and expanding the LabVIEW_Simulator folder in the Project Explorer window. Open any of the VIs and examine the block diagram to learn more information about how to generate biosignals in LabVIEW.
The Research Resource for Complex Physiologic Signals on the MIT-BIH database links to the popular site http://www.physionet.org/. The LabVIEW file For LabVIEW_Simulator_REQ2_REQ4.vi can be used to read biosignals saved in file formats from the physionet site. After you run this VI, the Configure Biosignal Import dialog box appears. Click the Browse button and navigate to any database file to retrieve the ECG segments in the file.
Converting Digital Biosignals to Analog with NI Data Acquisition Hardware
The DAQ_Simulator_Signal_verify.vi demonstrates how to use a NI DAQ device to acquire an analog signal then compare the acquired analog signal with the original digital signal. Open this VI and examine the block diagram for more information.
Take the following into consideration when you convert a digital signal into analog:
- The analog signal amplitude might suffer a large attenuation if the sampling rate is inappropriately low.
- The sampling rate of the analog signal must be the same as that of the digital signal.
- The resulting analog signal is in magnitude of volts, but you usually want them in magnitude of millivolts. You must attenuate the voltage.
The following figure shows an example of attenuation circuit from the AAMI standard:
Figure 2: Attenuation circuit for analog signal generation to ECG devices
The red arrow indicates the analog output in magnitude of volt, while the green arrow indicates the attenuated signal in magnitude of millivolt. The magnitude of the analog signal has been attenuated by 1000. After you generate the biosignal in LabVIEW, you can use the signal as the input signal to test the ECG instrument.
3. Artifact Traceability and Document Management as part of EC13
The NI Requirements Gateway improves the management of documents by linking traceability information from a wide range of sources. NI Requirements Gateway also allows information that may describe a Requirement or Test Method to be directly linked to LabVIEW test code. This capability enhances the quality of the verification process by eliminating manual error prone processes, while also allowing for automated report generation.
NI Requirements Gateway supports diverse types of documents, such as Text, Word, Excel, Visio, LabVIEW and others. You trace Requirements and Test Methods in your documents with specific grammar searching templates, which are defined by built-in or customized Regular Expressions. After you import documents, Requirements Gateway identifies the information in these documents via the regular expressions and performs automated analysis.
You must create your test documents before using the NI Requirements Gateway. Refer to the documentation on the NI Requirements Gateway for more information on how to create documents with built-in or customized regular expressions. The attachment includes example documents that you will need for ANSI/AAMI EC13 standard testing:
- Requirements of AAMI.txt—This file lists regulations that apply to medical devices within the scope of this standard. You can find the full requirement list in the official document for this standard.
- Test Methods of AAMI.txt—This file lists all referee test methods by which compliance of the device with the requirements above are verified. You can find the full list of test methods in the official document for this standard.
- Test Results.xls—This file contains the result for each test.
- For no_LabVIEW_Tests_REQ.xls—This file contains all test methods that you would perform manually without the use of NI LabVIEW.
- For_LabVIEW_Tests_REQ.lvproj—This file and its supporting files contain all test methods that you perform using NI LabVIEW.
4. Automate EC13 Testing Using NI Requirements Gateway
To add new requirements to the existing documentation, ensure that you add requirements in both the test requirement and method documents using the pattern of “NAME OF REQUIREMENT: BRIEF”. Also ensure that you cover the requirement using the pattern of “[Covers: NAME OF REQUIREMENT]” in the test method document, LabVIEW VIs, Excel documents, and so on.
Open the AAMI EC13.rqtf file to understand how you can use NI Requirements Gateway to organize these test documents:
- Open the Configuration dialog box by choosing File>>Edit Project.
- In the Configuration dialog box, you can add all test documents into the project and organize them properly. The following screen shot shows how the example project in the attachment organizes the test documents:
Figure 3: NI Requirements Gateway project window
In the Figure 3, five documents are imported into the example project and are divided into three layers. The top layer contains all test requirements, the intermediate layer includes the test methods and test results, and the bottom layer includes detailed implementation of the test methods. The arrows highlighted by red circles imply the traceability information.
- After you add the documents, click the OK button to close the Configuration dialog box.
- Click through the Management View, Coverage Analysis View, Impact Analysis View, Graphic View, and Requirement Details pages to learn how NI Requirements Gateway organizes your test documents.
Generate a report for the test by choosing Reports>>Project Reports>>AAMI Report1. The NI Requirements Gateway can extract information from any document that you add to this application and generate the final test report. You can customize the template of the report to obtain information you need. The following figure shows an example report that lists test names, requirements, results, and traceability information. This example also includes an overall description of the test, providing information such as coverage ratio, number of passed tests, and number of failed tests
Figure 4. NI Requirements Gateway test report
Refer to the documentation of NI Requirements Gateway for detailed information about managing your tests and generating test reports.
This article outlines the steps required to automate testing and traceability of tests and methods as defined in ANSI/AAMI EC13. A portion of all the tests are completed in the provided examples. You can add to each example and document template to create a complete set of materials.
Originally Authored By: Greg Crouch, National Instruments