Medical device usability as a factor in reducing error and improving
Human factors are key inputs in the design of medical devices,
especially with the increasing number aimed at patient use in the
home. Kay Sinclair & Natalie Scott
of Sagentia outline the issues involved and the implications of new
standards aimed at usability.
4 April 2011
The new set of human factors standards that were introduced in
2010 (HE75, the new ANSI/AAMI standard and the IEC62366) aim to address
the high number of medical device incidents that involve usability
By requiring companies to track user feedback and justify proposed
use error mitigation approaches, regulators are emphasising the
important role that usability plays in product safety.
These new regulations also recognise the fact that, as some
therapies transition away from clinical environments, medical
devices are increasingly being used by a patient population that has
less experience and training.
In addition to promoting safety, integrating usability into a
product development programme is quite simply good design practice.
In fact, a good way of adhering to the new standards is to:
- take a holistic view of usability and incorporate it as a
key component of every product development programme; and
- make sure that the specific market demands for each new
product are understood from the outset.
Why spend time on usability?
If people are involved in the use of a product, then human
factors should be core to that product’s development process. This
is especially relevant in the medical field where device
manufacturers need to improve patient compliance, prove
effectiveness and reduce safety risks.
For example, a diabetic who needs to take his or her medication
while at a restaurant will probably want something that is discreet,
fast and can be done — with one hand. An appropriately designed
insulin device will promote correct use and encourage regular and
maintained use of the device.
The fundamental goals of a medical device product development
programme are that the product works, is reliable for manufacturing,
meets end usage objectives and achieves target commercial return.
Although good usability design directly supports all three
of these goals, it is often sidelined, delayed or considered to be
an add-on to technical development. When properly integrated,
however, usability reviews provide the essential insight to balance,
help challenge, inform and direct technical decisions throughout the
development lifecycle. This leads to streamlined manufacturing, a
good user experience and better prospects for sound commercial
In extreme cases, poor usability can lead to product recalls
which are costly to rectify, and can also have a damaging effect on
a company’s technical and corporate reputation. The converse is also
true: a company that gains a positive reputation for the usability
of its products will benefit from increased customer loyalty,
reputation and hence sales across its entire product portfolio.
What's your approach to human factors?
Outlined below are three groups of usability tools that should be
considered as part of any product development programme.
Context exploration tools help define and understand the target
user(s) and their use environments. This will involve task analysis
and the exploration of use scenarios, potential user errors and
Exploring capability should also be a key part of human factors.
This involves exploring the physical, cognitive and sensory
boundaries of each user profile and should be used as a framework
throughout user testing. There are seven capability scales that can
be used in isolation to explore and improve the usability of a
device or concept.
User perspective exploration
User study tools can take different guises but the aim is to
explore potential use errors and hazards, user preference and
instinct, physical and cognitive demand, user performance and
capability boundaries, etc. This should include all influencing
users and a cross section of each user type as appropriate (ie
patients, care givers, health professionals, etc).
Justification and documentation
All FDA documentation now needs to include an explanation of the
company’s plan for managing and mitigating possible risks. There are
many tools that can be used to address this requirement. A single
document approach to tag and trace all potential usability issues is
perhaps amongst the best. Regardless of format, companies will need
to justify their device decisions from the perspective of the user.
In the past, the FDA may have accepted a design goal that “80% of
users must be able to open the device first time”, they now want to
know more about the 20% that couldn’t — what they did, why and what
is the resulting safety risk. A plan to mitigate or control expected
or actual usage error will also be required.
How do you integrate usability activities into your
current product development programme?
Human factors can be a key but flexible part of your product
development process. This can range from having a usability expert
challenge the product development at appropriate points, to a more
integrated approach that uses human factors tools throughout the
The main rule is that the specific nature and objectives of each
device is first understood. Deciding on the type, shape and size of
the human factors tools to use will then depend on a number of
factors. The following questions can help determine which tools to
use and how to use them:
- is this a completely new device for a new market or a
redesign of an existing device in a highly populated market?
- what is the complexity of the user interaction?
- what is the potential for and severity of harm that can be
caused by interacting with the device?
- what is the time and resources available to complete the
The impact of the new standards themselves will vary depending on
your current approach to usability. If human factors are not already
significantly incorporated into your approach, the new standards
should guide the tools you choose and how they integrate into your
process. Alternatively, should human factors be current practice,
these standards may simply direct how you document, trace and
justify the risk of potential usage error.
Usability issues in medical device sectors
Integrating human factors research into medical device design can
vary considerably depending on the device being developed, the
device category and the product’s specific objectives.
The usability of devices and equipment in the critical care
sector has always been of paramount importance. However, with the
current trend towards moving the treatment of many chronic
conditions out of the hospital and into the home means that the
challenge facing manufacturers of critical care equipment is even
Manufacturers need to consider how best to design for the future,
where the user may not be a highly trained nurse or technician, and
the environment may not be quiet, clean and closely supervised.
The FDA is pushing for this to be a consideration now, even if
the current generation of the device is designed specifically for
the hospital only. The aim is partly to save the time and cost of
subsequent product iterations for the home market, but more
importantly to prevent the inevitable safety risks that will result
from using a device that has not been designed for an untrained user
group or the home environment.
Drug delivery devices for personal use are well established.
Pharmaceutical companies are now not only focusing on device
performance and functionality but are also looking at device
usability as a primary differentiator.
For example, insulin pens have been available since the early
eighties and have evolved significantly over this time; starting
from a new exciting drug delivery approach with limitations, to a
focus on reliability and performance improvements, to more recently
an emphasis on usage improvements.
As with most drug delivery devices launched today, understanding
the range of patient profiles, the different attitudes towards
treatment, the varying years of experience and the differing
scenarios of use (amongst other characteristics) is key to a
The main trend in clinical diagnostic testing is the move away
from central laboratory testing to the point of care in the clinical
market. Some of these tests are already routinely used in the home
environment (eg blood glucose monitoring). Although these
diagnostics, and their results, are ultimately prescribed by the
healthcare professional, the devices themselves are increasingly
operated by the patient.
With the move towards the less skilled, and eventually, patient
use environment there are a number of usability factors to consider:
- understanding how the user interacts with the device;
- managing how the user understands, reacts and responds to
- ensuring the reliability of the device and the result, given
the variability of use conditions.
Whilst these are not insignificant challenges to overcome, there
are also additional points to consider. For example, the ethical
question of the types of diagnostic testing that should be
patient-driven. Where should the line be drawn between providing
devices that help people take control of their own health and manage
their wellbeing and assisting the worried well to self test,
diagnose and treat themselves?
Certain invasive diagnostic procedures and disease-specific
diagnoses will and should always remain in the hands of the
healthcare professionals. However, where there are diagnostic tests
and devices that will have a positive clinical impact by moving away
from clinical practitioners to patient self-use, human factors will
become an essential part of any potential development.
Surgical devices are used by highly trained medical specialists,
which results in the potential benefits of usability analysis often
being underestimated. However, in the often hectic environment of
the operating theatre, any interaction with the device that diverts
the attention of the medical specialists away from the patient is an
opportunity for improvement.
Examples of such situations are numerous and take many forms:
Optical aids such as surgical microscopes that are difficult to
adjust, buttons on devices that require the surgeon to change their
grip during the surgery or minimally invasive devices without
articulations that require the surgeon to adopt an uncomfortable
Packaging for disposable devices is another area, often
overlooked, which should be designed to make the transaction between
theatre staff and surgeon as easy and seamless as possible.
Two further trends that are putting new demands on usability are
the growth in robotic surgery, where the surgeon needs to
comfortably operate a remote control, and the increased use of
navigational technology in operating theatres, where physical
interaction with the navigation system and associated visual cues
are key and currently a foreign experience for the surgeon.
A standard approach
To date, human factors research has often been seen as an
activity that could be sidelined if budgets and time are too
constraining. However, the new standards are putting an end to this
A company that views usability as an integral part of their
design practice should find that the new standards require them to
simply document and justify their existing approach. In essence,
therefore, the standards should support the growing awareness that
the integration of usability work in the development process is just
good design practice that leads to better, safer and more usable
products. Device companies that understand this are also gaining
competitive advantage by offering differentiated and desirable
In order to ensure that an effective and efficient approach is
taken to usability, it is important to understand each specific
development programme’s use criteria and then identify the best
tools to use.
Different medical device sectors have varying needs and drivers
for human factors that will lead to different emphases. One thing
that is consistent, however, is that human factors research is
growing in importance, and will continue to do so, across all
medical device sectors.
Kay Sinclair, Managing Consultant, Sagentia Ltd.
Natalie Scott, Consultant, Sagentia Ltd.