The Food and Drug Administration (FDA or the Agency), the US regulating authority in the sphere of healthcare products, has published a guidance document dedicated to Brain-Computer Interface (BCI) devices. The present article address aspects related to the non-clinical bench testing for such devices.
Due to its legal nature, the FDA guidance does not introduce new rules or requirements itself but provides additional clarifications regarding the existing regulatory framework and recommendations to be taken into consideration by the parties involved in order to sustain compliance with the applicable regulatory requirements. The Agency additionally confirms that an alternative approach could be applied, provided such an approach has been approved by the regulating authority in advance and is in line with the provisions of current legislation on the matter.
According to the guidance, the particular testing methods to be applied in the course of the non-clinical bench testing should be determined depending on the design and functions of the BCI in question, including the expected duration of implantation, as it is important to evaluate the durability of the device. The appropriate testing should be carried out in order to validate the device’s conformity to the requirements set forth in the specification. The features of the device should remain intact during the whole period of the device’s expected life. For instance, the testing should include the assessment of the impact caused on the BCI device by body fluids. The acceptance criteria used in such testing should be justified in terms of the clinical use of the device. The authority encourages applicants to provide test report summaries, test protocols, and complete test reports. In this regard, the FDA also refers to its guidance on the Recommended Content and Format of Non-clinical Bench Performance Testing Information in Premarket Submissions.
The document further describes the requirements to be applied in the case of non-clinical bench testing of various elements of BCI devices.
As stated in the document, electrodes can be used to measure physiological signals or provide stimulation to the brain, spinal cord, and/or peripheral nerves or muscles for eliciting movement and/or sensation. The testing these elements should be subject to shall include the assessment of the following characteristics:
- Dimensional verification and visual inspection. The dimensions of the electrodes used in BCI devices should meet the requirements set forth in specifications thereto. The Agency emphasizes that the dimensions could impact the performance of the device, so the manufacturer shall pay special attention to the accuracy of dimensions and apply a risk-based approach with regard to toleration of deviations.
- Impedance. This criterion describes the conductive properties of electrodes, which are also important in terms of the future performance of the device. This aspect should also be addressed in specifications.
- Accelerated Lifetime Testing. In this way, the manufacturer assesses how the characteristics and features of the device would change during the expected lifetime. In particular, the assessment should cover both the physical and chemical stability of the device subject to assessment in a simulated environment that imitates the environment in which the BCI device is intended to be used.
Leads and Connectors
Other important elements of BCI devices are leads and connectors. According to the guidance, leads are used to connect electrodes to multiple components in an implanted BCI system, such as but not limited to processing hardware and power modules. The way these elements operate impacts the overall performance of a BCI device. The scope of testing to be conducted with regard to these elements should cover the following aspects:
- Dimensional verification and visual inspection.
- Leakage Current. In order to ensure the safety of a BCI device, it is important to prevent electrical shock or similar issues, so the leakage current should be subject to rigorous evaluation. In this regard, the authority refers to the applicable international standard ISO 14708-3:2017 Implants for neurosurgery – Active implantable medical devices – Part 3: Implantable Neurostimulators.
- Lead Body and Connector Flex Fatigue Testing. These aspects also should be assessed in the context of potential electrical shock or loss of recorded signal.
- Tensile Strength of Lead.
- Connector Insertion and Withdrawal Forces. The design of connectors should ensure uninterrupted connection during the use of the device and also resistance to the forces associated with insertion and withdrawal. In this regard, the authority recommends assessing the impact of multiple insertions and withdrawals.
- Particulate Matter Hazards. The Agency emphasizes that the release of particulate matter from any part of an implanted system that is intended to be in contact with body fluids during normal use is hazardous. Hence, the appropriate assessment should be carried out by the manufacturer of a BCI device in order to evaluate potential risks.
- Corrosion Resistance. Since these elements could be in contact with the human body, it is important to ensure their properties allow them to withstand the impact caused by such contact. In particular, it is necessary to assess the extent to which this will impact the performance of the device.
- Compliance with 21 CFR 898.12. The aforementioned regulation requires medical device manufacturers to ensure their products comply with the requirements set forth in the FDA-recognized voluntary consensus standard IEC 60601-1: Medical Electrical Equipment Part 1 – General requirements for basic safety and essential performance.
Implanted Casing and Electronics
The document also provides recommendations regarding the testing of electronics that, according to the document, are often implanted, covered in a can or similar casing, which serve to process signals received from the leads and/or to provide electrical stimulation signals to the leads. With regard to these elements, the regulating authority recommends carrying out the following testing:
- Hermeticity Testing. Should the level of moisture inside a casing exceed a certain threshold, this could impact the performance of electronics placed inside. Hence, it is important to ensure that casing is leak-proof.
- Environmental Testing. The element should be resistant to any impact to which it could be subject when used for its intended purposes due to the nature of the use environment. According to the guidance, the scope of assessment should cover such aspects as temperature changes (including temperature cycling); atmospheric pressure changes; and mechanical forces.
- Header Adhesion Testing.
- Battery. Should the battery be included in a device inside the implanted casing, it is vitally important to assess safety-related aspects associated thereto, especially the ones associated with potential overheating or short-circuiting in order to identify the risks patients could be subject to.
In summary, the present FDA guidance outlines the scope of non-clinical bench testing to be performed by the manufacturer of BCI devices. The document provides recommendations to be considered with regard to specific elements of such devices according to their functions and features.
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