Page 29 - Biomedical Engineering and Design Handbook Volume 2, Applications

8 MEDICAL DEVICE DESIGN

It doesn’t work that way unless a team is extremely lucky. The place to start is to define what is
referred to here as the need, with no regard to the means of meeting the need.
Before digging into the need definition process, the term stakeholder must be introduced. In this
context, the stakeholders are all of the individuals who are going to be affected by the introduction
of this product. There are often a large number of individuals represented here. They range from the
those who work in the manufacturing facility where the device is produced, to the patient who
benefits most directly, to the organization responsible for disposing of it when it is no longer func-
tional, with many people in between. All of these people have some interaction with the product, will
influence its effectiveness, and will in some way contribute to the success or failure of the venture.
The definition of need begins with the identification of the stakeholders and an evaluation of the
contribution each can make to the process.
The actual user of the device obviously heads the list of those who must be consulted, and this
discussion will focus on this individual first. This might be a surgeon, a therapist, a nurse, an
operating room technician, or some other member of the health-care delivery system. Regardless of
the role, the purpose of the device under development is to in some way assist that individual, to do
something that could not be done before, to make something easier to do, to make it safer, less inva-
sive, less traumatic, or in some other form more desirable. A chronic problem with designers is that
they try to make things better from their own point of view, rather than that of the user.
The knowledge that is sought from these stakeholders concerns the desired characteristics of the
product. What would make it a good or attractive device from their point of view? It is important
to maintain a separation here from any particular design or solution, and not to ask the individual to
“design” the device. (Although often they will wish to do just that.) As an example, a useful piece
of knowledge is that “the device should weigh as little as possible.” Some stakeholders will want to
suggest making the product out of aluminum or foamed plastic, in essence jumping over the issue,
toward a design solution. We know that choosing a low-density material is not always the best way
to attain a lighter weight in the finished product. By exploring the rationale for the suggestion, the
developer can get a clearer understanding of the user’s desires. Try to understand the attitude and try
and get it into functional requirements in the user’s own words.
In medical products the stakeholder group also includes the patient, and sometimes the patient’s
family. If we consider the external fixation device, the person most interested in keeping the weight
down is the patient who may be encumbered by it for a period of months. That is probably not the
only problem, however. In this instance, an effort should be made to locate a number of patients who
have had external fixations and gather the available information.
The patients never see many medical devices, so that the potential contribution from this source
must be evaluated for each product. Examine the circumstances carefully. The error that is often
made is to rely on the clinician to present the patient’s point of view. If the patient is conscious of
interacting with the device, he or she should be spoken to directly.
There are a variety of techniques for soliciting the opinion of the stakeholder in this context;
questionnaires, interviews, focus groups, and direct observations have all been used effectively. The
best choice in a particular situation will depend on many circumstances. It is important that the
choice not be based on convenience, cost, or time constraints, but on the nature of the product,
the state of development of products of this type, the user group itself, and a myriad of other issues.
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There are some concerns in selecting the individual users for this process. Von Hipple has iden-
tified a group of individuals he calls “lead users.” These are the pacesetters in the area in which they
work. They are always looking for new ideas and new ways to do things. Lead users should be part
of the user group studied for two reasons. They are often critical of ideas and are very helpful in iden-
tifying new directions. In addition, these individuals are often the first to be willing to try out new
products and their peers will look to them for guidance in this regard. It is also important that those
queried include representatives of average users of a product. It is possible to design a product that
can only be used by or is only useful to the a few practitioners at the very top of their field. Producing
a product of this kind can be prestigious, but it is seldom a good business decision. (There are many
examples of prototype and custom-built devices, particularly surgical instruments, made for these
individuals, that were successful in the hands of the target user but were not commercialized because
there was no expectation of a sizable market.)