Techniques for usability risk assessment during medical device design

Human errors during the use of medical devices, due to pitfalls in the design of the user interface, may lead to substantial risk to users and to patients. There are multiple techniques for the identification and for the assessment of user related risks, that may be chosen according to the step of the design (preliminary feasibility studies, minimum viable product assessment, verification and validation) and considering cognitive processes and information processing mechanisms of users, which may lead to errors. Some techniques are more adequate for a quick-and-dirty approach, during early stages of design: these include expert reviews, discussions among focus groups, standard reviews and heuristic analyses. Other techniques are adequate for a more detailed and systematic analysis of risk, in more advanced design stages, with a failure mode and effect analysis (FMEA) approach, including time-and-motion studies and task analyses. Lastly, user tests with the help of rapid prototypes, perhaps involving alternative embodiments to be studied, are very adequate for verification and validation of the interface. Usability analysis techniques should be part of the toolbox of a biomedical engineer and they should be carefully chosen. Each technique, regardless the step it is used, should allow the designers to define a precise level of risk in terms of probability, severity. Moreover, usability risk minimisation measures shall be measurable and able to be quantified, as well as the impact of risk mitigation strategies. For this reason, usability risk minimisation measures should be classified according to regulatory requirements as “safe by design”; “alarms and protections” and “information for safe use”. Each class of risk minimisation measure should be then given a measurable risk reduction score, so that the risk assessment can be completed in a repeatable and regulatory compliant way.