Considering the numerous standards and tests required to get a complex medical device to market throughout the production process will speed that device’s time to market.
Bill Stearns, Intertek
(Image by Glenn Garstens-Peters on Unsplash)
Active implantable medical devices (AIMDs) are complex products subject to rigorous regulatory standards. Most AIMDs include non-implantable supporting equipment, such as control and communication equipment, battery packs, implant kits, software applications, etc. Both require evaluation to regulatory standards.
Many devices also have electromagnetic compatibility (EMC) and wireless capabilities to consider. With a lengthy list of potential standards and tests, it’s important to know the requirements for a given product and consider them throughout the production process to get a compliant, marketable device to the industry.
Implantable components
ISO 14708 applies to the implantable device. It has seven parts; each outlines requirements for specific devices. All AIMDs must comply with Part 1, general requirements for basic safety and obligations for product marking and information/documentation. Parts 2-7 supplement or modify Part 1, taking priority. They are:
- Part 2, requirements for cardiac pacemakers.
- Part 3, requirements for implantable neurostimulators; aligns with ISO 14708-1:2014.
- Part 4, requirements for implantable infusion pumps; covers safety requirements illustrated via type-testing of samples.
- Part 5, which applies to circulatory support devices, excluding intra-aortic balloon pumps, external corporeal perfusion devices and cardiomyoplasty; specifies type tests, animal studies and clinical evaluation requirements.
- Part 6, requirements for AIMDs intended to treat tachyarrhythmia, including implantable defibrillators.
- Part 7, requirements for cochlear implant systems; includes type-test specifications.
Non-implantable elements
Non-implantable supporting equipment must be evaluated to specifications for electrical safety and performance found in IEC 60601 and IEC 62304. They are:
- IEC 60601 1, the general requirements for basic safety and essential performance of medical electrical equipment.
- IEC 60601-1-2, EMC requirements to ensure safety and performance in proximity to other electrical products.
- IEC 60601-1-6, the general requirements for safety and performance of medical electrical equipment. Collateral standard IEC 62366 covers the application of usability engineering to medical devices.
- IEC 60601-1-11, which includes requirements for equipment and systems used in home-healthcare environments.
- IEC 60601-1-12, which covers equipment intended for use in an emergency medical services environment.
- IEC 62304, which specifies life-cycle requirements for the development of software used in medical devices; includes provisions for risk management, maintenance and configuration.
Some AIMDs require specialized active equipment only used during the implant process. This equipment is also subject to the requirements of IEC 60601-1 and should be evaluated.
EMC and wireless considerations
Many AIMDs use wireless interfaces expected to maintain basic safety and essential performance without interfering with other electronics in their vicinity or the intended electromagnetic (EM) environment. Devices must maintain EM equilibrium when performing their designed functions.
Clause 27 of ISO14708/EN45502 outlines EMC evaluations to determine the effects of EMI on an AIMD. They confirm that implantable components exposed to EM fields do not experience unacceptable risk such as damage, heating or local increase of induced electrical current density. These assessments verify that the AIMD maintains basic safety and continues to provide essential performance, placing an emphasis on EMC risk management and analysis.
Each aspect of the AIMD that might affect performance when exposed to EMI should be tested in a scenario critical for patient outcome, based on risk. The standard expects and requires disclosure, explanation and justification for any unintended behavioral responses, which should be temporary and end with testing. Test labs must make accurate notes on behavioral responses during testing. Permanent changes in performance due to these tests, outside of specification, are prohibited.
AIMDs using wireless technologies such as Bluetooth, WiFi, wireless induction charging and RFID chips must meet requirements regarding coexistence, security and functionality. The most common sources for wireless standards are the International Electrical Commission (IEC) and the International Special Committee on Radio Interference (CISPR). Regulations cover output power, effective radiated power, occupied bandwidth, power spectral density, spurious emissions, frequency stability and specific absorption rate (SAR). These standards ensure the AIMD’s safety and performance as it interacts with other devices and functions within the body.
Best practices
A design review early in the process is critical when developing AIMDs. Reviewing the product, its intended use, potential user, environment and evaluation requirements can prevent costly mistakes by addressing and resolving them early. This can save costly redesigns and additional testing later, allowing you to avoid delays to market.
Given the number of tests to be done, conducting all evaluations simultaneously has several advantages, including time and cost savings, allowing economies of scale around risk management, software and usability. Reports can be streamlined, referencing each other without having to duplicate efforts. A single report package with all necessary information can be made and reviewed for a potentially faster product launch.
It is important to know which standards apply to a given product and to prepare for testing from the beginning. It’s also essential to complete evaluations in a timely, cost-effective manner to help bring these devices to markets across the globe.
Bill Stearns is a senior engineer on Intertek’s medical device team, serving as team lead for electrical safety of active implantable medical devices. He has more than 30 years of electrical engineering experience, with more than a decade focused on regulatory and compliance needs.
The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design and Outsourcing or its employees.
