As medical electrical technology has evolved along with other technologies, considerations for electromagnetic compatibility (EMC) have become increasingly critical. Because of this, the International Electrotechnical Commission (IEC) revised its standard for medical device EMC, IEC 60101-1-2, with a 4th edition, which goes into effect in the United States, Canada and EU in January 2019. With only a matter of months left until the compliance deadline, it is critical for medical device manufacturers to understand the requirements of the standard and how to demonstrate compliance.
IEC 60101-1-2 4th edition is the latest revision of IEC 60601-1-2, a collateral standard focused specifically on EMC for medical electrical (ME) equipment and systems. It provides guidance on EMC considerations and establishes requirements for manufacturers regarding environments for intended use, emissions and immunity testing, the risk management file (RMF) and a test plan.
Intended Use and Environments
Previous versions of the standard categorized ME equipment as either “life-supporting” or “non-life-supporting,” which does not take use environment into account. The 4th Edition eliminates the “life-supporting” and “non-life-supporting” classifications, focusing on where the device is used.
Previous versions also did not account for devices or systems used outside of professional healthcare facilities. It was assumed that ME equipment would be used in these settings and administered by healthcare professionals, where other electronics in the environment could be controlled at a higher level. With the growth of home healthcare and wireless, connected technology, it would be unrealistic to continue to keep these expectations in place. Instead, the 4th edition establishes three categories of environments in which ME equipment may be used:
- Professional Healthcare Environment: This includes the settings covered in previous editions, such as hospitals, physicians offices, surgical centers and limited care facilities. In these settings, the equipment or system is administered by a professional and there is more control over the environment as a whole.
- Home Healthcare Environment: This new category includes settings such as homes, schools, churches, restaurants, hotels, cars and airplanes. It is not guaranteed that the device will be controlled by a medical professional. Additionally, there is less control over other electronics in the setting, which may be numerous and varied.
- Special Environments: The third category covers military areas, oil and gas refineries, appliance manufacturing or heavy industrial areas. These specialized areas differ from both a professional healthcare setting and from a home setting, and may offer unique challenges in terms of location, other electronics and potential interference.
When designing and developing ME equipment, it is necessary to establish the intended environment and then consider what type of EMI the equipment or system may encounter in the given environment. Ventilators and defibrillators will have differing EMI considerations than cell phones and radio devices, for example. Intended environment is also a factor for considerations such as level of control and potential users.
Emissions and Immunity Testing
Another major change in the 4th edition is the inclusion of new requirements for emissions and immunity testing. For emissions testing, the ME equipment must be evaluated to CISPR or IEC standards for radiated emissions, conducted emissions, harmonics and flicker. Specific requirements for a given device will depend on the intended environment and usage. Additionally, some emissions requirements have been removed. Wireless devices must also comply with wireless standards in place for the device, as well as ME equipment standards and the emissions requirements of the 4th edition.
The more significant testing changes under the 4th edition are the requirements for immunity testing. Electrostatic discharge criteria have been adjusted, as have those for bursts, surges, power frequency magnetics and voltage dips, dropouts and interruptions. The 4th edition also provides requirements for both radiated and conducted radio frequency (RF), with changes to dwell time being prominent.
Essential performance, or the performance necessary to achieve freedom from unacceptable risk, is a critical component of immunity testing. Essential performance is most easily understood by considering whether or not its absence or degradation would result in an unacceptable risk. It can be defined using certain applicable standards, collateral standards and considerations of what the product is, its function, intended setting and end user.
When testing for radiated RF immunity, basic safety and essential performance must be maintained throughout testing, with a performance exception for RF receivers in place. In-band testing still takes place, but a degradation of performance is expected. The dwell time for testing is based on the settling time of the test system and the adequate time for the device under test to be exercised and affected. If either basic safety or essential performance do not hold up during testing, the ME equipment system has failed the test.
The revisions under the 4th edition include robust risk analysis requirements. Because the range of potential issues arising from EMI is so wide, the 4th edition requires manufacturers to manage risk by identifying the following:
- Reasonable foreseeable electromagnetic disturbances
- Risks associated with those disturbances
- Ways to mitigate or eliminate these risks
All of the above is done during the risk management process and documented in a risk management file (RMF).
The RMF must illustrate an understanding of a device’s function, performance and basic safety in relation to EMC. Additionally, a thorough, well written RMF shows compliance to the 4th edition standard. As such, it is one of the most important documents in the product development process.
In previous versions of the standard, the need for risk analysis and management was implied and specific instructions related to them were not offered. As a result, RMFs often fell short when it came to addressing EMC. To combat this, the 4th edition requires that the RMF contains the following:
- Justification for the environment category specified for the device, as well as whether or not the product is life-supporting
- Specific and detailed immunity pass/fail criteria for both safety and performance related to EMC
- Immunity pass/fail criteria that specifies acceptable degradations that will not result in unacceptable risk
- Details as to how the product will be monitored to demonstrate compliance to the established pass/fail criteria
- Documentation and justification for any cause for increased or decreased testing levels
- Operating modes that maximize emissions, as well as those that are problematic
- Active and standby modes considered “worst case.”
- The highest acceptable risk for a device, the risks to test against and the modes and settings that demonstrate compliance to the 4th edition standard (established prior to immunity testing)
Once developed, the RMF should be used to design a test plan that includes information from the RMF such as intended use, intended environments, test levels and immunity pass/fail criteria. This requirement for a detailed test plan is another new requirement under the 4th edition. The test plan must be submitted to the test lab prior to testing and used as the guiding document in the execution of testing. Any deviations from the test plan must be documented within the test report.
The RMF and subsequent testing must be used later to develop user instructions that communicate: Intended environment, essential purpose, safe distance warning and instructions for maintaining basic safety and essential performance, including those related to EMC.
The importance of EMC in ME equipment and systems cannot be understated or underestimated. In today’s world, and in the future, these products will be around, and impacted by, other electronic devices. EMC has the potential to create problems that range anywhere from mild nuisance (an alarm going off unnecessarily) to potentially drastic (device malfunction or stoppage). For these reasons, compliance deadlines to the 4th edition of IEC 60601-1-2 are quickly approaching. It is critical for manufacturers to learn and prepare for the standard to bring compliant products to market quickly and easily, filling the need for all stakeholders.