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.
So what does this mean in the context of designing in wireless capabilities? Mostly it 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 these 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:
First, you should understand the characteristics of the RF channel. This means considering the effects of data throughput, latency and loss that could be expected. Stated many times throughout the document; it’s pretty clear they mean it. Effects on device controls, interlocks and alarms should be considered.
The second big issue is security. Not just to the transmission of patient data, but also to 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 and further software data security may be required.
EMC is a third area. Just like 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 makes a polite request to keep the transmitted power as low as possible while still maintaining safe operation of the device.
The use environment is a fourth area to consider. 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. Conditions that might be expected in the use environment should also be considered, 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 is a fifth area. Does the user have enough information to safely install and use the device? The FDA goes into detail about the sorts of additional information the user may need due to the inclusion of wireless functionality.
Finally the FDA draws attention to aspects of the product life cycle with regards to wireless technology. For instance, RF or EMC components of the system may require regular inspection, testing or calibration.
There is more in the document than I’ve covered, but you’ve got an idea of where it’s going. If you’re familiar with the risk-based approach now required with the third edition of IEC 60601-1 there will be nothing out of the blue, just some useful reminders of things to consider.
Kenneth MacCallum, PEng, is a Principal Engineering Physicist at Starfish Medical. He works on Medical Device Development, including devices involving the third edition of IEC 60601-1, and would be very happy to hear your thoughts and experiences regarding the new FDA guidance.