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Evaluating FDA Guidance for RF Wireless Technology in Medical Devices

Mon, 10/07/2013 - 8:55am
Kenneth MacCallum, PEng, Principal Engineering Physicist, Starfish Medical

Last month, the FDA issued a guidance document for RF wireless technology in medical devices. Not surprisingly, the FDA is recommending a risk-based approach to design, testing, deployment, and maintenance of medical device development.

This follows the risk-based approach to safety that was introduced in the 3rd edition of 60601-1. With that revision, the process of developing a medical device must include an integral component of risk management. In other words, the process must include documented iterations of identifying, evaluating, and mitigating risks of harm to the user or patient.

What is the impact on designing in wireless capabilities? Primarily, this means considering as many ways as possible that the device could become unsafe for either the user or the patient due to the inclusion of wireless features, evaluating their expectation of harm and mitigating as necessary.

To help with this process, the FDA addresses a number of specific areas to consider:

Characteristics of the wireless technology and its Quality of Service (QoS): The effects of the characteristics of the communication channel such as data throughput, bit error rate, latency, and loss that could be expected should all be considered. When evaluating the probability of the risks caused by these characteristics, published or measured data should be used when possible. Also, think about effects on device controls, interlocks, and alarms.

Security: This goes beyond just the transmission of patient data, but also tampering and unauthorized or unsafe control of the device. The FDA makes special mention of potential risks relating to intended and unintended communication with other devices as well as risks associated with automatic discovery mechanisms of protocols such as Bluetooth. Although a number of protocols include encryption methods, these may not be enough to mitigate a particular risk sufficiently and further data security augmentations may be required.

EMC: As with unintentional emitters, devices with wireless capabilities are covered by standards such as IEC 60601-1-2. Interestingly this standard makes an explicit immunity exemption at the transmitter and receiver frequencies. The onus is on the design team to evaluate the risk of interference at these frequencies. The FDA also recommends that the transmitted power be kept as low as possible while still maintaining safe operation of the device to reduce the chances of interfering with other devices in the vicinity.

Use environment: Wireless device effects on typical equipment in a normal use environment and the impact typical equipment may have on the wireless device are especially important given the likelihood of popular protocols being used nearby. Examine conditions that might be expected in the use environment, such as higher absorption for implanted or body-worn devices, or high ambient electric or magnetic fields. Care should be taken during the environmental evaluation to understand world-wide differences, such as RF bandwidth allocation or the proliferation of particular coexisting devices.

Risks associated with device use: Does the user have enough information to safely install and use the device? A list of additional information that may help the user operate the device safely is listed in the guidance document, including protocol description, RF frequency and power, warnings, etc.

Product Lifecycle with regards to wireless technology: For instance, RF or EMC components of the system may require regular inspection, testing or calibration. They also recommend including wireless considerations in the implementation of corrective and preventative action. Could failures or malfunctions in the field be caused by the inclusion of wireless technology or perhaps by the interaction between the wireless technology and the particular use environment?

All of this probably will not be surprising to engineers familiar with the 3rd edition of 60601-1. The FDA is recommending selecting a wireless technology with a Quality of Service which will maintain a suitably low probability of harm. They also recommend considering and evaluating the risk if harm related to adding this technology based on QoS, security, EMC, use environment, device use and product lifetime. The document makes these straight-forward suggestions and furthermore recommends what additional information should be included in a premarket submission of a medical device which includes wireless technology.

My evaluation is based on experiences working on Medical Device Development at StarFish Medical, including devices involving the third edition of IEC 60601-1. I’d enjoy hearing thoughts and experiences from readers regarding the new FDA guidance.

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