Medical devices rarely fail because they do not function. More often, they fail because the development team does not understand real use and real life intervenes.
A product can work perfectly in controlled testing and still falter in a rushed morning, in a dimly lit bathroom, in a hospital ward at 3am, or in the hands of someone who is tired, stressed, or distracted.
That was the thread running through our conversation with Natalie, a human-centred design and usability engineering specialist who has worked in MedTech since the mid 2000s, largely within Cambridge based consultancies and now supporting early-stage product development teams.
We began with a simple question: why do products that “work” in controlled settings struggle in the real world?
From design engineer to “the person who engages with users”
Natalie trained as a design engineer. Early in her career, she noticed the importance of stepping outside of the development team to obtain user insight and enable the design team to make informed decisions.
A key part of her role became to engage with the users and feed in their perspective.
Not to collect opinions, but to observe user behaviour. To watch what people actually do when they are tired, rushed, distracted, stressed, or simply human.
That has defined her career.
In medical devices, it also became unavoidable. As usability engineering standards became embedded within the regulatory landscape, it was no longer optional. Demonstrating safe and effective use became part of proving the device itself was safe and effective.
Where things quietly go wrong
Often, usability is treated as something that happens towards later stages of development, when many aspects of the user interface have already been defined. Teams often focus efforts on tweaking the design of the user interface for the final summative (validation) study, which is submitted to regulators to demonstrate that real users can operate the device safely and effectively.
That study is important and is a key part of the Usability Engineering file.
However, if usability is left until this stage, many of the most consequential design decisions are already embedded . Adjustments become expensive, slow, and sometimes structurally difficult to implement.
By that point, the opportunity to shape behaviour through design has narrowed, which is often the most effective and efficient means to address usability issues and control use related risks.
Natalie’s view was that the application of usability engineering should start far earlier – before the concept generation stage. Prioritising what matters most from the human perspective early, enables teams to make informed design decisions and develop the right concept from the outset.
If a cue on the product suggest the wrong action and the user interface allows incorrect use, there’s an opportunity for people to follow that misleading design cue and encounter use errors, even if the written instructions say otherwise.
What usability engineering actually means
Natalie described usability in three layers:
Safe
How might someone be harmed if they used it incorrectly? What are the key use-related hazards and potential use errors you need to worry about and design out where possible?
Effective
Can the user complete the tasks as intended and receive the intended benefit?
Something people will actually use
Even if a device is safe and effective, if it is frustrating, slow, confusing, inconvenient or unsatisfying , people avoid it. In healthcare, that can become non-use, non-compliance, or misuse.
At that point, usability stops being a design detail. It becomes a real-world issue. If people cannot comfortably integrate a device into their daily routines, during stressful moments, at work, at home, or on public transport, it will not deliver its intended impact. Usability determines whether the technology genuinely supports people in everyday life, not just whether it works under ideal conditions.
Reading the product, not the manual
One of the most practical parts of our discussion focused on cues.
People do not read your mind. They read your product.
A shape that looks like a button invites pressing.
A surface that resembles a grip invites holding.
A click can sound like completion.
A tone can feel reassuring, even when it should signal caution.
These cues are sensory, not just visual. Sound, touch, resistance, vibration, even the way packaging opens.
When cues, context, and instructions align, safe and effective use becomes more likely. When they conflict, users will often follow what the product suggests rather than what the manual states.
This is not about blame. It is about alignment between intention and experience.
Watching behaviour, not intentions
When we asked what innovators could act on immediately, Natalie suggested a simple approach for conducting early stage usability research:
Put a prototype (low or high fidelity) in front of individual representative users (a small sample of say five to ten users is typically good enough for early-stage research) and ask them to pretend to use it (assuming it is safe for them to do so).
Give minimal, but a representative level of guidance.
Quietly observe what they do and which parts of the user interface they interact with.
Take notes on whether their actions match your intentions.
Resist the urge to step in until the participant has finished their simulation. Then afterwards, explore why they did what they did, to understand the root cause of their actions and behaviours.
It can feel uncomfortable. But stepping in too early removes the opportunity to identify where the design is unclear.
That said, timing matters.
At very early stages, some additional guidance and context setting may be appropriate. If a concept is still forming, confusion may reflect immaturity rather than usability. The “no helping” approach becomes most valuable once the core interaction is sufficiently defined to stand on its own.
You do not need a large study to uncover meaningful insight and identify key usability issues.
But it helps to know when to step back.
The whole system, not just the device
Another important thread in our conversation was that “the user” is rarely just the person holding the product. It’s important to understand the broader “human” relationships with the product and their perspective.
In healthcare, it may include the patient (or the recipient of the product benefit), clinician, nurse, carer, buyer, maintainer, trainer. The different use scenarios and the environment in which the product is used or stored can also significantly influence the use of the product, whether that is a home, hospital ward, ambulance, gym bag, or bedside table.
It’s also key to consider the whole system – all aspects of the user interface that may influence use or the user experience. The user interface includes the packaging, instructions for use, accompanying Apps and websites, and of course the device.
A beautifully engineered device can still fail if it does not fit within the care pathway.
This is where usability intersects directly with value proposition, service model, route to market, training burden, health economics, and clinical outcomes. It is not separate work. It is the same work, viewed from the human side.
Learning from what has already gone wrong
Natalie also encouraged looking outward.
Public incident databases linked to regulators can contain reports of individual use errors or recurring patterns of known usability problems across product categories. The data is not always clean, but it reveals something important: people will surprise you, and they will do so repeatedly.
Learning from this data and these patterns early allows teams to design with foresight rather than hindsight.
Why this matters to us at LYEONS
At LYEONS, we are building in a space where everyday use matters deeply. If someone is stressed, tired, overwhelmed, or dysregulated, their cognitive bandwidth is reduced. That is not an edge case. It is often the baseline reality.
So usability is not a final regulatory step for us. It is part of protecting people from avoidable friction, confusion, and risk.
We continue to study how supporting physiological regulation, sensory experience, and clear human-centred interaction can help people feel calmer, safer, and more able to engage with daily life.
We are grateful to Natalie for taking this journey with us as LYEONS evolves, and for helping us keep usability close to the heart of how we build.
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