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Features

The medical device market has been rapidly changing over the last decade and a key area of change is addressing today’s fast paced data-driven environment. Multiple sources state the digital health market to currently be a greater than $5 billion industry, with growth predictions to be over $90 billion by 2025. Factors in the growth of electronics integration into medical devices range from the need for accuracy of the device performance in the surgical suite to an individual patient’s desire for monitoring their own health.

Fig. 1 – Technology Comparison: Data Rate, and Range
Medical device companies face many challenges in matching today’s technology desires while balancing strong industry cost pressures. Every feature and every benefit needs to be balanced against cost to result in a successful value-based solution. Integrating electronics into medical devices becomes even more challenging when the device is disposable.

However, single-use and single patient devices can have different considerations. A single-use disposable is designed and approved for one-time use, such as a hand-held surgical device requiring electronic integration to provide and monitor balloon pressure. A single patient disposable is designed for and allowed to be used multiple times by the same user. Examples include an inhaler or drug-delivery injectable pen. Both can be successful utilizing integrated electronics. In balancing features and cost for either application, a good place to start is the design.

Design Considerations

Designing or even redesigning an existing product to include electronics requires an understanding of user needs, available technology and its limitations, and the complicated maze of regulations that control these products.

Regulations for electronics in medical devices vary greatly from their non-electronic counterparts as well as from country to country. When the new product development calls for an electronic/electro-mechanical solution, the following should be considered.

Human Factors: Integrating electronics may open vast possibilities for the human interface but careful consideration must go into understanding the target user. This is no longer just a common sense thing to do; it is now required by the FDA. ISO 13485:2016 explicitly references Usability Standard IEC 62360 which is a part of the overall compliance to IEC 60601. IEC 62360 is harmonized by the European Union as well as the United States and can be used to satisfy the regulatory requirements of both markets.

Battery Life: Battery life can be the most challenging obstacle in implementing a disposable or single-use medical device with integrated electronics. This is compounded further if the device also needs radio frequency (RF) communication or a display with backlight. Advances in low power microcontroller architecture and higher density battery technologies have opened up new opportunities.

Environmental Concerns: Ambient light or backlight, temperature, humidity, storage conditions, and chemical exposure all play a role in the component selection and the sealing requirements (IPXX).

Interface Requirements: While many devices only provide user feedback via indicators or displays, some may require communication to another device like a smartphone, access point, or directly to the cellular network for communication to a distant location for remote monitoring. Direct cabling has largely been displaced by wireless communications via RF or infrared (IR) links. IR links offer lower cost and less stringent regulatory requirements but are limited to line of sight communications and are directional. RF communications offer much wider options. That brings in the next challenge discussed below.

RF Communications: International standards vary widely in both the frequencies allowed as well as power level, so the device destination is needed early in the design phase. A comprehensive study of the international frequency allocation is necessary. In the US, there is a specific frequency allocation for implantable (400 Mhz) and Wireless Medical Telemetry Service (WMTS): 608 to 614 Mhz, 1395 to 1400 Mhz, 1427 to 1432 Mhz - mostly US only. Devices that are placed within 20cm of the patient require routine monitoring to demonstrate compliance with the FCC radiation exposure guidelines.

Once the market homework has been completed, the RF protocol must be decided. This can vary from a completely dedicated design and proprietary protocol to one of the popular short-distance communications protocols, such as Zigbee™ or Bluetooth™ and midrange communications, such as Wi-Fi, which operate in the ISM (Industrial, Scientific, Medical) band: 902 to 928 Mhz and 2.4 to 2.5 Ghz. For longer distance communication, direct cellular connection has become the most popular. Battery life considerations will likely rule out cellular for a disposable device.

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