Usability engineering for Medical Devices

Written by Luke Sy on 19th Aug. 2020

The goal of usability engineering, also known as human factors engineering, is to design (medical) devices where human error is made unlikely as it can be, through inherent safety by design, process controls, or by providing safety information. In the webinar, Sue Lynch from Medtech Pathways gave us a wonderful overview of usability engineering where she described to us the steps involved in the standard IEC 62366-1.

Overview of steps involved in IEC 62366-1

5.1 Prepare use specification 
5.2 Identify user interface characteristics related to safety and potential use errors
5.3 Identify known or foreseeable hazards and hazardous situations
5.4 Identify and describe hazard-related use scenarios
5.5 Select hazard-related use scenarios for summative evaluation
5.6 Establish user interface specification
5.7 Establish user interface evaluation plan
5.8 Perform user interface design, implementation and formative evaluation
5.9 Perform summative evaluation of the usability of the user interface.

Device Use and Hazards

The first five steps were about identifying the device use and the associated hazards. One must clearly describe the intended medical use, users (e.g., is the device gonna be used by a child, bystander, or clinician?), environment, and operating principle (e.g., which part of the body the device will interact with). After identifying device use, one must identify the serious harm (i.e., life-threatening or permanent damage) that can arise from the incorrect use of the device, and make sure that this scenario is included in the summative evaluation. Certain aspects of hazard identification can be done with ISO 14971 Application of risk management to medical devices, and taking note of FDA guidance for similar devices is highly recommended.

Evaluation of device usability and safety

The last four steps were about the evaluation of device usability and safety. It involves two types of evaluation: formative and summative. One typically starts with a formative evaluation which is typically informal and involves a smaller test population (N=5 to 10). The device can be a mock-up or a rapid prototype. The goal is to do an early exploration of usability and to feed those insights quickly into the product design. Once you are confident with the design, you can proceed with the summative evaluation on a decent number of users (N >=15) with the actual device in a real environment. If the device is intended for multiple types of user, the summative evaluation must be tested on each type of user (e.g., the user must demonstrate the use of device independently, perhaps after training). The summative evaluation can be seen as an overall validation of usability design. Lastly, note that compliance with IEC62366 doesn’t guarantee the satisfaction of FDA guidance.