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The Issue of EMI in the Medical Industry

Updated: Nov 23, 2020

Between the years of 1979 and 1993, there were more than 100 reports of medical equipment failure attributed to EMI in the United States. The FDA believes this number is most likely inaccurate and that EMI incidents were and continue to be under-reported due to a lack of knowledge on the subject. In the ‘80s and ‘90s, apnea monitors and electric wheelchairs demonstrated equipment malfunctions attributed to EMI. Sixteen thousand apnea monitors were recalled in the ‘80s due to EMI susceptibility. In the ‘90s, after electric wheelchairs malfunctioned from EMI and flung users into traffic, new standards were drafted and implemented.

While EMC testing has been around for years, many devices are still susceptible to EMI, especially in the medical industry. With the advent of cellular, IoT, and wearable devices, the number of medical equipment failures attributed to EMI has risen. Even devices that were shown two decades ago to be susceptible to EMI still face vulnerability.

Take pacemakers, for instance. In the ‘90s, researchers discovered that nearby cellphones could interfere with pacemakers and defibrillators. Modern pacemakers are designed to sense signals outside of the usual frequency range and, subsequently, pace in a backup safety mode. Other variables, however, can affect a pacemaker’s susceptibility to EMI. For instance, outside signals can interfere with pacemakers’ bidirectional radio telemetry systems, which allow technicians to send commands to the technology. RF physiotherapy equipment and electro-surgery can also interfere with pacemakers. External pacemakers, in particular, are susceptible to EMI because they do not possess additional shielding from the body.

Cellphones play a particularly interesting role in medical device malfunction. Many of us have seen the hospital signs that say no cellphones allowed beyond this point—and many of us have ignored these signs. Cellphones will typically only affect medical devices when in close proximity, but the effects can sometimes be life-threatening. ECGs, EEGs, pulse oximeters, infusion pumps, ventilators, and defibrillators are all susceptible to EMI from cellphones at a distance of less than 1.2 meters.

So why are medical devices so susceptible to EMI? Well, the hospital environment is partly to blame. According to research, 63% of all E field measurements within hospitals exceed IEC immunity requirements for medical devices. Power lines, patient monitoring equipment, electrosurgical units, radios, and VDUs account for the strongest sources.

It is estimated that a whopping 90% of medical devices fail EMC testing the first time around. In addition, 97% of this failure is attributed directly to EMI (other variables include packaging and labelling errors, among other things). If a medical device is not designed with EMI in mind, it will most certainly fail EMC testing. EMI must be considered from the very beginning of the design cycle to ensure that the device’s layout is flawless and will not cause any issues.

Failing product testing can cost your company a lot of time and money. It can substantially delay your time-to-market, affect your company’s credibility, and cost you thousands of extra dollars in testing. Designing for EMC and pre-compliance testing are two essential steps in the design process that will ensure your product has the best shot at passing EMC testing the first time around.

When it’s time to test your medical device, give Rhein Tech Laboratories a call. Our engineers have tested and certified thousands of products and possess extensive experience with hardware product development with an emphasis on compliance engineering designs. Our clients rank us as the best EMC testing lab around, with five stars in schedule flexibility, pricing, turn-around time, technical competency, and customer service.

Unlike other testing labs, we won’t send you back to drawing board if your product fails. Our engineers will evaluate your product’s design pitfalls and EMI sources and then provide you with the solutions to fix these issues, guaranteeing your product passes its second round of testing.

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