This blog post will take you through some of the common questions we get from engineers, designers and project managers who are new to human factors and usability engineering.

What is HF?

Human factors. Ergonomics. Usability engineering. In the medical device world, at least, these are all interchangeable terms. Human factors is a scientific discipline concerned with understanding human behaviour and the physical and cognitive attributes of end users. By understanding end users in this way, designers and engineers can ensure that their medical device is designed to enable safe, effective and comfortable use.

Although Human Factors evolved from other industries such as defence, oil and gas, and transportation, with the Chartered Institute of Ergonomics and Human Factors and Human Factors and Ergonomics Society being two of the main HFE communities in the UK and US respectively, the discipline is now well and truly embedded in the medical device world.

Do I need to perform any usability engineering for my medical device?

In short, yes! Whatever your medical device is, you should be considering the end user from the earliest possible moment. You may not need to perform any formal human factors studies, but you should, at least, be doing some risk-based analysis to ensure and document that any use-related risks are effectively managed. This work typically starts with defining who will be using your medical device, the environments it will be used in and for what purpose or scenarios the device aims to meet user needs. Once this is fully defined you can begin to explore potential use-related risks. This being the primary focal point of the regulatory bodies, rather than usability facets such as efficiency or satisfaction.

What is use-related risk?

Anyone working in medical device development will be familiar with taking a risk-based approach and human factors and usability engineering is no different. No matter how complex your device, you should take a rigorous approach to identifying possible use-related risks and opportunity for use error.

There are many ways to conduct a use-related risk analysis (URRA) for your medical device. One commonly used tool used is a Use Failure Modes and Effects Analysis (uFMEA). Such tools typically start with a task analysis which is a detailed, systematic list of all the steps required for your medical device to be used correctly. A task analysis really can form the backbone of good usability; it can be used for risk analysis, usability study planning, definition of user interface requirements, development of instructions for use and much more.

With a detailed task analysis, you can begin to identify what a user might do incorrectly, or indeed not do at all – these are known as use errors. For each user error identified, the potential hazard to the user or patient can be determined and potential harms established. For more detail on this see our post on use-related risk.

How can human factors help improve my medical device?

Understanding how end users behave and the potential harm they could be exposed to will enable you to implement suitable mitigations and design barriers. Your use-related risk analysis should be a living document, describing mitigations put in place as the device design develops. Testing of these mitigations can also be documented to chart the ‘story’ of development and help explain design decisions to regulators when you come to submission.

What is a human factors or usability study?

Human factors or usability evaluation can be done in a number of ways – see our post on human factors evaluation techniques. One of the most common approaches to testing a medical device during development is a formative usability study where you put your device in the hands of representative end-users. A study like this typically involves 5-8 participants representing each of the intended user groups for your medical device. Each participant will use a prototype of your device and be observed for any use-related issues they might have. Read our post on how to perform usability studies for more information.

Findings from usability tests should be fed back into the use-related risk analysis for your medical device and be used as inputs for the next phase of product development. For medical devices that require evidence of human factors testing, you will need to perform a validation study.

What human factors documents do I need in my design history file?

When it comes to submission you will need to ensure that the regulatory bodies can easily trace your usability engineering process. This will start with documents like your use specification, which should clearly identify the intended use, users and use environment for the medical device. You will also need a use-related risk analysis documenting the potential harms associated with use of the device; this might form part of your overall risk management file.

All usability study documents including protocol and reports will also be part of the design history file for the medical device. You may have a user interface specification that fully describes all components of the device’s user interface. Finally, you’re going to need a Human Factors Summary report that brings the ‘story’ of your device development, risk management and usability testing together.