The science of human factors

Cambridge-based Medical Device Usability recently embarked on a research project to analyse the design fundamentals of autoinjectors. In this article, managing director Richard Featherstone explains the background to the project.

The science of human factors has only relatively recently been applied with any rigour to medical devices. Of course, everyone wants to develop a product that meets the needs of its users. In the old days an odd focus group here or there, and getting your favourite medics to try it would just about do it. And the marketing campaign would boldly state that their new product is ‘easy to use’, without actually providing any evidence to back up the claim.

But, like any science, the knowledge base expands, practitioners apply a more rigorous approach, and of course the regulators take a keener interest. So it is with human factors. In large part driven by the FDA, manufacturers are struggling to get up-to-speed with the requirements. What doesn’t help is that there is, sadly, very little published usability data on medical devices. Manufacturers have understandable concerns about commercial confidentiality, given that most usability work is carried out during the pre-market product development phase. In contrast to their clinical studies, most pharma companies do not publish their human factors data.

Whilst this protects their intellectual property, it has the effect of creating a void. Anyone who wants to develop a new device, for example an autoinjector, has almost to start from scratch, answering such fundamental questions as how large should the device be? Should it feature a button? What is the best colour to use in the dose indicator window? Should it click once or twice (the answer is twice by the way).

We at MDU are uniquely placed to gather usability data from across a wide range of medical device types, and user types. We are independent of any product development agency; we give unbiased, objective advice, based on our wide experience of testing devices. So we decided to fund our own independent research to investigate some of the fundamentals of design for autoinjectors, and to publish the findings.

And because we are not tied to any design agency, we have no preconceptions, and no vested interest in promoting any one solution over another. We wanted to get to the truth about user preferences for the key aspects of device length, diameter and colour.

So we recruited patients who use autoinjectors for a range of conditions, in the United States and the UK. People with autoimmune conditions such as rheumatoid arthritis and Crohn’s disease, male and female, right handed and left handed across a range of ages and ethnicities.

Using plain block models with neutral grey colouring to isolate the key factors of length and diameter. We are experienced enough to know that user perceptions of a device may change once they use it, so we explored perceptions of usability before handling them, and after they had used them to simulate the injection process and compared the results.

We also took the opportunity to gather anthropometric data such as hand length and width, to investigate whether hand size influenced the views of users.

Moving onto colour, most designers realise that colour can be a powerful signal. In the context of autoinjectors, it is vital that users can deliver the full dose of medication safely and effectively. Users need to know whether a device is ready for use, whether it is full or empty and from which end the needle will emerge. Colour is increasingly used by designers to try to communicate these and other messages. But to return to an earlier point, there is almost no published data on colour meanings in the context of specific device types like autoinjectors.

So we investigated the meaning of colour in the context of self-injection. If the window of an autoinjector turns red, what do users think that means? What if it turned yellow? Again, these seem like fundamental questions that should have been settled years ago. Well now they have. And more too.

We are proud to be one of the world’s leading researchers in the field of human factors applied to medical devices. Our work helps some of the world’s leading companies to develop great devices and get them approved. To find out more, and to get a copy of our published work, go to www.medical-device-usability.com.