By William Hyman, ScD
How do you determine the expected life of a medical device? Even if the device is working properly—in addition to being well maintained and inspected—an adverse event following its so-called “expiration date” can raise both usability and liability challenges. On the other hand, damage that occurs prior to the expiration date may render the device unusable as well, begging the question of how to correctly determine when a product is no longer able to be safely used.
As an example of the expected life of a medical device, consider a standard bed rail. In one instance, the manual for the bed rail notes that its expected service life is two years from the date of purchase. This is explicit and could be considered a purposeful short-life statement, as the manufacturer knows the bed rail could have durability issues in terms of usage. It is also vague with respect to failure mode. (Health Canada, for instance, has cited worn rail latches as a cause of serious patient injury.) The short life also strongly suggests planned obsolescence by the manufacturer.
Following the manufacturer’s suggested life would lead to the purchase of new rails every two years, which may be ideal for the vendor, but less so for the buyer. Such planned obsolescence was at one time decried as a waste of resources and the unnecessary creation of trash. However, waste concerns predate cell phones and other technology that has led to the annual purchase of the latest model as expected—and even preferred.
A short-life statement also benefits the vendor by limiting liability for devices that remain in service for a long time. This may be driven by the problem of “legacy” bedrails being a large issue for bed manufacturers when standards and expectations change, such as those related to entrapment. Although I have not studied it in detail, I believe this explicit statement of life expectancy is rare for a non-sterile device.
Identifying Shelf Life for Non-Sterile Devices
In the case of a sterile device, recognizing shelf life is easy since the packaging has a pull date. Some non-sterile devices may also have a “shelf life,” although even a 1991 FDA Guidance Document on shelf life is not clear if that definition only applies before the device is first used. Non-sterile, “durable” devices are another matter; the length of the warranty may be a guide, but the warranty period also tends to reference the time period for manufacturer-funded repairs as opposed to expected life.
The FDA is less than helpful in defining expected life, describing it as the time that a device is expected to remain functional after it is placed into use. Aside from date-labeled devices, the definition goes on to say that devices are expected to remain operational through activities such as maintenance, repairs, or upgrades, for an estimated period of time.
Unfortunately, how that estimate is to be made is not addressed. The FDA does require that some devices adhere to tracking regulations in order to effectively locate devices affected by health notifications or recalls. However, tracking regulations are limited and in most cases, only require tracking for the “useful life” of the device. In other words, the tracking requirement does not help identify the useful life of the device in the first place.
Even so, there are some third-party lists meant to guide expected useful life of medical devices. One such list, complied by the Biomedical Engineering Advisory Group, provides 16 factors that might affect useful life, ranging from familiar use and user profile to business, safety, strategic, and political risks associated with continued or discontinued use. But even utilizing a guide presents challenges. For instance, do you use the device up to the last day of the listed life, stop using it early as a measure of caution, or continue to use it past that date with some level of risk assessment and extra scrutiny?
Offering another perspective, the International Organization of Standardization 14971 asks for a determination of expected service life under its risk management provisions, but it is not clear if the determination is required on labeling. It has also been suggested that a manufacturer’s design controls should be considered in determining useful life. Although not explicit, the FDA design input regulations state that the manufacturer has to establish design requirements that are appropriate and address the intended use of the device. From that perspective, it appears that those requirements should include how long the device will last.
In conclusion, determining an expected life of new medical devices is not easy, unless the product is clearly labeled. Aside from clear vendor guidelines, labeling or generic life tables, useful life and useful remaining life is best determined by active monitoring of current condition and frequency of repair. This can be combined with an understanding of likely failure modes and whether failure is expected to be with or without warning. It is also prudent to be prepared to explain—possibly in retrospect—how you determined that a device continued to be suitable for service.
- 21 CFR 803.3. Available at: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?fr=803.3
- Shelf Life of Medical Devices. Available at: https://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM081366.pdf
- Medical Device Tracking. Available at: https://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/PostmarketRequirements/MedicalDeviceTracking/default.htm
William A. Hyman, ScD, is professor emeritus, biomedical engineering, at Texas A&M University in College Station, and adjunct professor of biomedical engineering at The Cooper Union, New York. Questions and comments can be directed to 24×7 Magazine chief editor Keri Forsythe-Stephens at [email protected].