The Food and Drug Administration (FDA) has completed guidance for medical equipment Electromagnetic Compatibility (EMC) information to be submitted before an electrical medical device that is manufactured in the United States is marketed. This guidance updates previous submission recommendations released in 2016. Its intent is to provide clarification of what the FDA will consider in its premarket reviews.
The FDA is requiring the sponsors of most medical devices to adopt to the new guidance but is extending the period to one year for In Vitro Diagnostic (IVD) devices. While this guidance refers to electromagnetic compatibility, the guidance applies to both interference and immunity.
Electromagnetic Compatibility (EMC)
Electromagnetic compatibility refers to the requirement for electronic devices to not interfere with the normal operation of other equipment in its shared environment. All electronic products are sources electromagnetic energy. This energy may be transmitted both in radiated and conducted forms.
Radiated energy may be comprised of digital signals generated by the circuitry, energy generated by Point of Load (PoL) voltage regulators, or inappropriate usage of intentionally radiated Bluetooth or Wi-Fi signals (e.g. transmission protocol or excessive bandwidth). Conducted emissions are those that are introduced onto power lines or interconnecting cables.
Electromagnetic Interference (EMI)
EMI can be generated by environmental factors. The Sources of naturally occurring EMI include:
- Radio Atmospheric – (Sferic) Broadband impulses that occur as a result of lightning.
- Solar Radiations – Including Solar Flares and Aurora Borealis resulting when charged particles emanating from the sun interact with Earth’s magnetic field.
- Cosmic Noise – Radiation caused by planets and other stars other than the sun. (Generally, this does not pose a significant risk to modern electronics.)
EMI can also be caused by other electrical and electronic systems in the proximity of the device of concern. Potential sources of interference include any number of analog or digital sources. This energy can be classified into broadband and narrowband.
Broadband EMI is usually from unintentional radiators. Sources of broadband include power convertors, electrical motors, and digital circuits. Narrowband is usually generated by intentional transmitters. These include TV and radios stations, cellular phones, Wi-Fi and Bluetooth devices.
EMI can enter a circuit either by radiated energy or energy coupled onto wiring such as power inputs. These energies are further categorized into radio and magnetic. Magnetic refers to low frequencies generally below 100 kHz. Radio extends from 100 kHz to the GHz range.
Other sources of interference include power fluctuations, surges, and disturbances, and Electrostatic Discharge (ESD).
Medical Product’s Intended Environment
Information required by the FDA includes that the product designer define the environment of intended use. A modern medical facility is packed full of electronic devices that can be effected by electromagnetic energy. Many of these devices have safety critical functions that if effected could result in life threating events. These devices include defibrillators and ventilators.
A test summary should be provided on all testing performed on a finished product. This summary should include data, pass/fail criteria, and any allowances, deviation or modifications.
Defined Modes of Operation
The FDA is also requiring that manufactures define the device’s functions and modes of operation. There is an emphasis on defining which modes would be most at risk for EMI events.
FDA Adopts Consensus Standard IEC 60601
The IEC 60601 series of standards address hazards to to electrically powered medical equipment (ME) and ME systems. They include many specific standards that address specific categories of devices such as sterilizers, infusion pumps, and centrifuges.
IEC 60601-1-2: 2014 includes risk management requirements in form of an assessment be performed before testing to determine immunity test levels and pass fail criteria.
This analysis must be conducted by the manufacturer. It should define the essential performance for each essential function of the device to be tested against the factors likely to be encountered in the intended environment. These factors include radiated energy sources, conducted sources, electrostatic discharge, and power fluctuations and disturbances.
After this assessment is performed a list of relevant immunity test methods can be selected at realistic levels can be documented in a test plan. This test plan, again, is the responsibility of the manufacturer to create.
CVG Strategy Expertise
CVG Strategy EMI/EMC consultants can provide susceptibility analysis for medical equipment EMC requirements and recommend appropriate test methodologies to ensure reliable operation of safety critical products. Our team has decades of experience in automotive commercial, aerospace, and defense sector testing. We can also provide assessment for coexistence of products using Wi-Fi protocols.