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International Standards for Design-to-Market Wearable Medical Devices
Over the past 20 years, Digital Health technologies have been embraced as a panacea of our healthcare system. In 1977 we marveled at the first calculator watch from HP; which was followed by the “digital revolution” of health research, paralleled by the MEMS sensor technology revolution, all of which have changed how design engineers think about data sensing and storage. As a result, by 2012 there were various mobile apps for health applications and 2013 was dubbed as “Year of the smart watch”. Being worn on the body, wearable electronic devices allowed the user to continuously track health parameters, providing reliable and accurate measurements capturing meaningful data previously unavailable to consumers. With an exponential growth in technology components, the functionality of these devices expanded beyond tracking to increased individual awareness of health, helping people to be healthier.
Through innovation-friendly approaches and industry engagement over the past 10-13 years, the regulatory and standards bodies brought to focus the functionality of these devices over the digital platform they reside, channeling the innovations around their “medical deviceness”. As a result, there are now some significant wearable medical devices used in healthcare settings. Their form factor has also evolved from being conforming to parts of the body to the skin. With their comfort in wearing, miniature designs, different form factors and interconnectivity, these devices offer endless possibilities for healthcare, moving from a “curative” to the ‘4P approach’ (predictive, preventive, personalized and participatory), long advocated by Leroy Hood and other pioneers of systems medicine. The personalized attention, participation of stakeholders in decision making, preventive measures and predictive capabilities enabling quick therapeutic intervention are all now possible.
Considerations in designing Wearable Medical Devices
As a procedure set up by the regulatory authorities for approval, clearance, or license to manufacture, distribute and sell the wearable “medical devices” (WMD), they would be classified using a risk-based category. While the classification categories vary from country to country, the fundamental approach is to determine their classes by the manufacturer’s intended use of the device and specific indications of its use; and on the risk of the device for the patient’s health/life and for other users (i.e. CA – Class I, II, III, IV; EU – Class I, IIA, IIB, III; FDA – Class I, II, III; all in the order of increasing risk).
The international standards also support this approach. They enable the development and manufacture of a safe wearable medical device by design, minimize the risk in every stage of product life, and prove its real clinical benefit. Standardization of the clinical risk assessment, quality management, and safety testing processes offer a common framework for stimulating the innovation and providing credibility and global recognition of new products. The knowledge of the international standards supporting the three key pillars – quality, safety, benefit – will largely help management and designers alike to define and embed regulatory constraints during product ideation, design, pre- and post-market clinical validations and product evolutions.
Consider the example of a vital sign monitoring skin patch device (FDA Class II) increasingly being used for the application of remote monitoring of outpatients and general patients care in hospital setting. This product is also cleared by FDA for its use on COVID critical care patients undergoing therapeutic treatments. The skin patches incorporate multiple sensors, smart processing of the patient data, alarms to support medical decisions and continuous interaction with the medical practitioners. For these devices, variables such as accuracy, time stamp between measurements by different sensors, their absolute location on the body would all relate to the performance under its intended use. External environmental influences, training or skill level needed for the users, patch wear duration, use on general care versus critical care patients, interference with other devices such as a pacemaker on the patients, are just a few factors developers must consider for their impact on clinical decisions to be taken by health professionals.
Another skin patch device (also FDA Class II) with a huge impact on clinical benefit is a continuous glucose monitoring device, wherein an enzyme coated needle sensor penetrates the skin to access the subcutaneous layer beneath to sense glucose in the body fluid. The other components of the device are an applicator of the needle, a transmitter, and an app for analysis of the data. The device is interoperable with other medical devices such as an insulin pump. The exact positioning of the needle sensor, adhesion of the patch to the skin for a prolonged period, patient comfort during wear and change, mechanical and electrical integrity of the patch, sensor and transmitter, time lag of the device in detecting glucose limited by the transport of the body fluid, inaccuracies of false alarm signals are some of the considerations associated with the device. Interesting to note is that the FDA has approved several Class III continuous glucose monitoring devices between 2005 and 2018, which are more invasive than the skin patch Class II device (mentioned in the above example). This is a progress in the right direction addressing diabetes management; at the same time reducing the regulatory burden.
For both examples, a good quality design and manufacturing practice starting with design planning, design control and change procedures, methods, and processes to address software vulnerability, cybersecurity, safety of data communication and transfer, basic electrical safety, EMC, biocompatibility and a good clinical practice for pre- and post-market clinical investigations are required to sufficiently address their various risk factors.
Standards Relating to Wearable Medical Devices (WMDs)
The following international standards offer a cohesive approach to address these considerations and overcome regulatory constraints for the successful launch of WMDs and expansion of their impact on healthcare:
- The ISO 14971: Application of risk management to medical devices is a global standard process for identifying and controlling risks at all stages of the device life. Its application proves the WMD is free of any structural defects that could pose risk for patients and other users or compromise correct functioning. Appendix C of ISO 14971 lists questions that the developers could use to determine the risk profile for the device. It is a core document for a risk-based approach, all other standards are aligned to this. li>
- The ISO 13485: Medical devices - Quality management systems - Requirements for regulatory purposes, is a Quality Management Systems (QMS) standard that provides guidance not only for good manufacturing practices but also for design control, especially the section 7.3 of the standard. Risk-based approach to different stages of the design is the key difference between this and ISO 9001. Compliance to ISO 13485 is a requirement for CA and EU. US FDA has its equivalent quality system; however, a transition is imminent. It was originally planned for 2020 but delayed due to the pandemic. li>
- The IEC 62304: Medical device software — software lifecycle processes, is a functional safety standard and covers safe design and maintenance of software, firmware or embedded or Software as a Medical Device (SaMD). Practice of QMS is a pre-requisite for its application. It uses ISO 14971 for defining Class A, B, C of the software based on their risk. It is also in close parallel to the umbrella functional safety standard IEC 61508, used for Industry 4.0 situations.
Clinical data is precious. Therefore, special regulations apply to medical devices from the cybersecurity point of view. While waiting for a harmonization and international convergence of cybersecurity principles and practices, the International Medical Devices Regulators Forum (IMRF) has published an international guideline document in 2020 (IMDRF-Principles and Practices for Medical Device Cybersecurity). Its focus is on medical device security and therefore it is limited in scope to address the potential for harm to the patients. It also does not address organizational security related to manufacturers or healthcare institutions. HIPAA’s security rule and NIST Framework addresses both patient security and organizational security. It is a risk-based approach applicable to devices containing software, including the firmware and SaMD. Because of its risk-based approach the guide falls in line with IEC 62304 as well as ISO 14971. The guideline also deals with pre-market and post- market considerations. For example, cybersecurity management plan, customer security documentation, vulnerability disclosures coordinated among the stakeholders are some of the recommendations.
- The ISO/IEEE 11073 is a set of 31 active standards in the Health Informatics/Medical Device Communication family. This package contains the general communication and transport protocols for point-of care medical devices and a variety of personal health devices (PHDs) anywhere from BP to glucose meter to body composition analyzer. The most recent publication of ISO/IEEE 11073-20701:2020 Point-of-care medical device communication – Service oriented medical device exchange architecture and protocol binding considers the device interoperability issues. li>
- The IEC 60601-1, often called as collateral standards, is a widely accepted series of international standards for the basic safety and essential performance of medical electrical equipment. Applicable to WMD are: Part 1: applicable to wearable devices classified as “applied parts” (e.g. electrode connected to an ECG monitor); Part 2: for EMC requirements and tests; Part 6: for usability requirements; Part 8: for alarms and indicators; Part 10: for devices in closed loop system; Part 11: for devices in the home settings. For a particular type of medical equipment, say ECG, 60601-2 Part 25 and 27 would be used in conjunction with 60601-1 for safety testing. li>
- The ISO 10993-1: Biological evaluation of medical devices: Evaluation and testing within a risk management process, is needed to address the risk associated with biocompatibility as most wearables come in contact with the skin, more so the skin patches. Toxicity testing for components of the sensor in direct contact with body fluids may also be needed in anticipated exposure cases. The ISO 10993-Parts 12, 17, and 18 will apply here. li>
- The ISO 14155: Clinical investigation of medical devices for human subjects — Good clinical practice (GCP) provides guidance to manufacturers and clinical research professionals on how to implement GCP for pre- and post-market clinical investigations. The result of applying this standard demonstrates that there is a statistically significant relationship between performance and clinical benefit. Protection of patient rights, ethical consideration for the design and conduct of the trials on humans, and credibility of the clinical evaluation are some of the key benefits of following GCP. This standard also requires “clinical risk management” added to the list of sponsor responsibilities. This introduces the concept of clinical quality management processes, implementation, and oversight, even if this task is outsourced to a third-party clinical research organization (CRO).
The real clinical benefit of WMD technologies could only be achieved following a risk-based approach for their development. A clear identification of intended use and indications for use are important, followed by a good risk profile of the WMD. The international standards covering QMS, risk management, clinical trial management, and design for safety in pre- and post-market developments, offer opportunities to improving WMD’s performance and expanding their healthcare applications.