While all electronic products must comply with electromagnetic compatibility (EMC) requirements, EMC evaluation of medical devices is expanded to include product safety. This step-up is understandable as human health and life are frequently dependent on medical devices in a healthcare setting.
A medical product usually gets tested and evaluated according to a version of IEC 60601-1-2 based on the country it will be marketed for. However, the current standard does not cover a few potential hazards; a new version is being developed to further minimize the risk of electromagnetic interference. Manufacturers of medical devices should be aware of requirements in the works to be able to plan for future compliance and address them in the product design and development phase.
EMC in Medical Devices Now
The Essential Performance and Basic Safety (EP&BS) criteria evaluate a medical device’s intended use and operation and its features or functions that might cause harm or injury to the user, patient and surroundings. Minute degradation of features and functions is allowed, provided it does not affect essential performance and safety of the product.
EMC-compliant medical devices produce electromagnetic disturbances that do not affect either their EP&BS or the correct functioning of other equipment. Therefore, the very first stage of planning for EMC compliance is defining the product’s EP&BS and designing EMC compliance around these criteria.
According to IEC 6060-1-2, devices are tested for emissions and immunity. The emissions test evaluates the RF energy the product puts out, and the immunity test determines the product’s performance according to its EP&BS criteria under the electromagnetic effects. All operational modes should be considered for testing in full or partially to determine compliance for the overall system.
Why Is the Standard Getting Stricter?
Wireless in Healthcare: Proceed With Extreme Caution
Wireless devices are easy to set up and access, have low power and cost requirements and a short frequency range. It is hard to imagine the healthcare environment without them, even though they bring along a number of associated risks.
60601-1-2 currently states that as long as the radio has been tested and found compliant with the relevant radio standard, and the limits of the radio standard are equivalent or more stringent than the 60601-1-2 specifications, no additional testing is needed.
While this concept makes sense, the wireless communication aspect of a device is often considered an important part of the product’s EP&BS criteria. Therefore, testing the entire system with a wireless communication device on is critical in evaluating the system’s performance (including the wireless communication part) for both emissions and immunity tests. After all, any malfunctioning could result in data interruption, distortion or delay, negatively affecting a patient outcome. The manufacturer should address the wireless communication concept of a device during the product’s safety risk assessment to determine any risks of wireless malfunctioning.
RF Proximity: a Missing Part of the Puzzle
There are other risks associated with the use of wireless devices in the healthcare environment. Figure 1 is an example of a small medical care facility where two patients are connected to medical devices using wireless technology, and the data is transferred to a monitoring station.
Potential interference between the devices and ambient noise should be tested according to the current EMC standard. However, no current requirements mandate a device be evaluated for RF proximity. This holds true, even though some of the 60601-1-2 immunity test frequencies might correspond to the existent frequencies of RF communication technologies, or if a manufacturer considered this type of interference and did some preliminary testing of its own. It is difficult to determine the test strength as it would depend on the proximity of the devices. It is to provide coverage for this type of interference that the IEC is introducing new EMC requirements for medical devices.
Wireless Coexistence: Interoperability Is the Goal
The Food and Drug Administration’s (FDA) “Draft Guidance for RF Wireless Technology in Medical Devices” defines wireless coexistence as follows: “an ability of one wireless system to perform a task in a given shared environment where other systems have an ability to perform their tasks and may or may not be using the same set of rules.”
The majority of wireless devices operate at an unlicensed ISM band. When they are located close to each other, interference is likely to occur in their transmission. Currently, no specific standard or requirement explains in detail how to ensure interoperability between devices. IEEE 802.15.2 and IEEE1900:2, along with the FDA’s “Radio-Frequency Wireless Technology in Medical Devices,” could be used to understand the concept and build a plan for a specific device. Any associated risks should be included within the device’s safety risk assessment process and documentation.
What to Expect
In reviewing the expected changes to the new standard below, please keep in mind there might be some updates by the time the standard gets published and becomes mandatory. The new standard will introduce (Figure 2):
- New product categories depending on the environment (hospital, small clinic, home and transport)
- Test levels per new product categories
- New safety and performance requirements for the equipment
- Safety engineering into medical EMC / Risk Management
- Increased immunity test levels to minimize the risk of electromagnetic interference
The new version of the standard will require almost all devices within its scope to be re-tested partially or in full, depending on the product’s category and safety and performance criteria. Upfront planning and preparation are essential for a successful testing campaign. Manufacturers are advised to factor in the EMC phenomena into the EP&BS criteria during a product’s design phase and consider the upcoming changes in addition to the current requirements to ensure full compliance.
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