Human-machine interaction in health care should not be taken lightly. Poor medical device design can cause tragic and sometimes fatal use errors. To prevent these kinds of incidents, the IEC 62366-1 standard on usability engineering for medical devices was created. The user experience (UX) team at NOVO, which is well versed in usability engineering methodologies, summarizes the essentials here.
The goal: design products that are safe to use
IEC 62366-1 is the international standard for usability engineering in medical product development. The term “human factors” is also used to describe this approach, particularly in the United States, by the Food and Drug Administration (FDA). For both the IEC and the FDA, the goal is to design a device’s user interface to minimize the risk of use errors. Although the process itself is presented as a recommendation, manufacturers are obligated to provide objective evidence that a device is safe to use.
Applying the recommended methodology throughout the product development process increases the chances of designing a safe product, and therefore obtaining certification from regulators.
Use error, a core concept
The IEC 62366-1 standard was created in response to major incidents resulting from use error. For example, infusion pumps and tube fittings have led to use errors that have caused serious injury to patients, and even some deaths.
The standard is based on the principle that use errors can be eliminated or reduced by implementing a user-centred iterative design process.
A brief definition of usability
Usability is the extent to which a product can be used by specified users to achieve specified goals with success and satisfaction in a specified context of use.
For IEC 62366-1, usability is assessed based on the following main criteria:
Effectiveness
The accuracy and completeness with which a goal is achieved (e.g., the user injects the correct dose of an intravenous drug).
Efficiency
The resources required to achieve a goal (e.g., the time a user needs to correctly configure an infusion pump).
Satisfaction
The lack of discomfort and positive attitude about using the device.
Learnability
The time and effort needed to become familiar with the device and how it works.
It ties in with the ISO 14971 risk management process
To define what can be considered safe use, IEC 62366-1 looks to the ISO 14971 standard. While the latter specifically addresses the application of risk management to medical devices and supports a decision-making process, the usability engineering process in IEC 62366-1 focuses on design and development.
Benefits above and beyond user safety
Although the process described in IEC 62366-1 is mainly intended to protect the public, it has numerous other benefits for manufacturers:
- Better management of development time and costs
- Compliant and convincing documentation to submit to regulators
- Fewer training and technical support needs due to a more intuitive interface
- Increased sales stemming from higher user satisfaction
The user interface is much more than what’s on screen
In usability engineering, the term “user interface” covers all the ways in which the user and device can interact, from hardware to software. In addition to graphical user interfaces (GUIs), this definition includes all formal aspects, weights, dimensions, textures, sounds, etc.
It’s worth noting that instructions and training are also considered part of the user interface, since they affect its use.
A process inspired by user experience (UX) methods
Whether it’s to define the user needs and use environment, carry out a risk analysis, or perform formative and summative evaluations, the user experience (UX) methods recommended by IEC 62366-1 are essential to the usability engineering process:
- User interviews
- Contextual inquiry
- Heuristic evaluations (or ergonomic audits)
- Cognitive walkthroughs
- Usability testing
Formative evaluations, or why it’s normal to not immediately get a satisfactory result
Under IEC 62366-1, adopting an iterative approach is crucial: creating multiple versions of the solution before going to market is a must.
Once a prototype can be put together, whether that’s a conceptual model for a graphic user interface or a volumetric model for a physical product, an initial formative evaluation should be conducted. The findings are recorded, the design is improved, and a subsequent evaluation is carried out.
Early formative evaluations typically don’t involve users, but it’s a good idea to get a prototype in their hands sooner rather than later (i.e., to conduct early usability testing).
The closer the development process gets to wrapping up, the more the formative evaluations should reflect the product’s actual use in terms of the test environment and user profiles.
The summative evaluation, or the final exam
The IEC 62366-1 standard requires a summative evaluation, which is the final step of the process. This evaluation aims to gather objective evidence that the product can be used safely.
To do that, the use of the medical device should be simulated with at least 15 participants from each profile.
For example, if a device will be used by nurses and physicians, 30 use simulation sessions should be held. The testing conditions should mimic the real context of use as closely as possible, including for training and documentation. Additionally, it’s recommended that the summative evaluation not be conducted by people who are directly involved in the development process… who obviously would not be the most objective.
After analyzing the root causes of the use errors that occurred during the test, if it turns out that the residual risk is unacceptable (which is a matter of risk management under ISO 14971), the summative evaluation is considered a formative evaluation. Such a scenario has major impacts on the project schedule and costs, which is why it’s important to carry out formative evaluations all throughout the process.
Ways to optimize the process
During the projects we’ve done here at NOVO, we’ve found that the following points are key to implementing effective usability engineering:
The planning
Since usability engineering eats up time and resources, planning it into the project schedule and budget is essential.
The expertise
To obtain valid results, research involving users must be carried out by specialized professionals using a rigorous methodology.
The documentation
As with any quality management process, everything needs to be documented to show the entire process and justify all safety-related design decisions.
Agility
When it comes to the iterative side of the process, it’s important to be open-minded, agile, and accepting of the fact that the solution will need to be adapted as findings come in from the formative evaluations.
The collaboration
It’s in all the design team members’ interests to be aware of the matter. Usability is everyone’s business, whether directly or indirectly!
