Chapter 9. Summary
The examples in this book represent only a fraction of the current mistake-proofing
methods and devices in the health care industry and only hint at the possibilities
of how mistake-proofing could be applied. The implementation of mistake-proofing
does not require starting from a standstill. Instead, existing solutions should
be implemented wherever appropriate throughout each health care organization.
Where ready-made solutions do not exist, designing, fabricating and installing
new devices will be required.
Mistake-proofing is a change of focus, requiring more attention to the detailed
design of processes, so that the easy way (or, ideally, the only way) to perform
a task is the correct, efficient, and safe way. Mistake-proofing involves changing
the physical attributes of a process. Consequently, mistake-proofing devices
usually can be photographed.
Implementation of mistake-proofing in health care settings will be accomplished
by putting knowledge in the world, designing benign failures, preventing failures
in the work environment, detecting errors, preventing errors, and preventing
the influence of errors. It will require the employment of devices that mistake-proof
the actions of care providers, patients, and patients' family members.
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Tables 9.1-9.5 recap the composition of the mistake-proofing examples presented
in this book as they were categorized in Chapter 1. Although the selection
of these examples was not intentionally biased, a distinct and restrictive
definition of what does and does not constitute a mistake-proofing device affects
these findings. Mistakeproofing is relatively narrowly defined here when compared
with other authors' definitions.1,2
For example, Godfrey, Clapp, Nakajo, et al, include actions such as "train
laboratory technicians to... empower all employees to... encourage
patients to... clarify with physicians..."1
You cannot take a picture of these actions, so, while they may be worthwhile
and effective actions, they would not be included here. Therefore, the proportions
of examples reported in the tables do not provide a carefully constructed statistical
sample that warrants populationwide conclusions. These tables suggest areas
that lack medical mistake-proofing examples and call for new contributions
to the body of knowledge.
Preliminary data from the example collection process suggest that many of
the mistake-proofing examples included here have been broadly implemented in
health care. Many device examples were submitted by people from differing organizations
and geographical regions, and several were featured on commercial equipment
or supplies. No locally developed devices were reported more than once. Further
research is necessary to definitively determine if the implementation of certain
commercially available mistake-proofing devices is widespread, as the preliminary
data suggest. Findings of widespread implementation would be encouraging, suggesting
that the health care industry is amenable to these devices.
Table 9.1 shows how the devices from this book are distributed among Tsuda's3 four approaches to mistake-proofing. One-half of the devices are designed to
directly prevent mistakes by prohibiting them from taking place. Another 28
percent represent changes to the work environment intended to prevent mistakes
in indirect ways, by removing ambiguity and making correct actions more obvious.
Twenty percent of the devices rapidly detect errors, enabling staff to respond
quickly and prevent more serious errors. Among those collected, only a few
examples of preventing the influence of mistakes were identified.
Table 9.1 Mistake-proofing devices categorized
by Tsuda's3 four approaches to mistake-proofing
||Percent of total
|Mistake prevention in the environment
|Preventing the influence of mistakes
Table 9.2 shows the distribution of devices that utilize the different setting
functions identified by Shingo4 and Chase and
Stewart.5 More than one-third of the devices, 35.3
percent, are physical setting functions. This percentage would not be unusual for
any mistake-proofing application or, for that matter, any industry. The more
interesting number is the 36.0 percent of information enhancement setting functions.
Chase and Stewart wrote about this type of device over a decade
ago.5 They added information enhancement devices to
those proposed by Shingo4 in the belief
that this type of mistake-proofing would be needed in services. The fact that
over one-third of the devices are in this category supports their belief.
Table 9.2. Mistake-proofing devices categorized as
||Percent of Total
|Grouping and counting
Table 9.3 indicates the distribution of the collected mistake-proofing devices
when categorized by control function. Shutdown and sensory alert devices are
the most common control functions. The overall distribution of devices is somewhat
evenly distributed among the control functions.
Table 9.3. Mistake-proofing devices categorized by
control (or regulatory) function
||Percent of Total
Note: Numbers may not total 100 due to rounding.
Table 9.4 divides the mistake-proofing devices discussed in this book into
the six categories defined by Chase and Stewart.5
These categories are divided into those concerning errors committed by customers
(non-health care personnel) and errors committed by service providers (health care
personnel). Of the collected examples, 24.66 percent address errors that would be
committed by customers. Of these, almost 90 percent are mistake-proof aspects of
the service encounter.
Few examples exist in the areas of preparation and resolution. The remaining
75.33 percent focus on the errors of health care personnel. Not surprisingly,
the vast majority of provider devices, 62.50 percent of the total and 84.07
percent of the provider devices, address task performance errors, and 14.16
percent address errors associated with the tangibles delivered to patients.
Only two (1.77 percent) devices collected ensure that patients were treated
in a respectful and professional manner. This does not mean that patients were
treated badly, only that few physical devices aided in providing proper treatment.
This analysis suggests the existence of a broad area of opportunity to identify
or create additional mistake-proofing devices that address customer preparation,
customer resolution, and provider treatment. The realization of these opportunities
will result in a perception of more patient-centered care by everyone involved.
Table 9.4. Devices categorized by areas of focus
for service provider and customer mistake-proofing
|Type of device
||Percent of devices segregated by customer or provider
||Percent of total devices
One of the more surprising findings of this project has been the scarcity
of locally developed or "do-it-yourself" examples (Table 9.5).
Locally developed devices custom-made by process users are pervasive in industrial
companies that have implemented mistake-proofing. The relatively few examples
in health care may be partially explained by the fact that most industrial
companies have a machine shop and tool and die makers readily available to
fabricate any mistake-proofing device they need. To compensate, health care
providers will need to develop external sources of expertise.
Table 9.5. Proportion of purchased mistake-proofing
|Source of device
||Percent of total
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Sources of Supply
Although some mistake-proofing devices that will be needed in medicine will
be created in-house or in an individual's garage or workshop, others
will require more sophisticated design and production help. Competencies in
inventive processes, design, fabrication, and assembly will be needed in some
cases, and not all medical organizations will have these capabilities. These
competencies usually will be found in engineering, maintenance, or biomedical
engineering departments. In the absence of these departments, organizations
must find other sources of supply.
One place to begin the search for help in developing a prototype for minimal
cost is the engineering school at local colleges. Occasionally, engineering
students may undertake projects as part of a class. Engineering programs will
typically have two types of classes where devices could be designed and fabricated:
"senior capstone design" courses and independent research courses. Organizations
should expect to provide funding for required materials, but they may be able
to avoid labor costs and profit margins. Squire6
... the school be physically close ... you want to be able to go
there and explain the idea ... undergraduate engineers have a tendency
to go off on their own, and without being available to see the development,
you may end up with something very different than you envisioned.
Convincing an engineering school to adopt the project will also depend on
the level of difficulty and whether the project requires a combination of competencies
that would be beneficial to the students. This approach requires diplomatic
treatment of intellectual property issues and commercial contingencies.
Karen Cox, a Patient Safety Improvement Corps (PSIC) 2004 participant, spoke
of needing a farmer to weld a piece of equipment to solve a problem in the
area of human factors and forcing functions.
The hooks that hold the containers in the infusion pump in Figure 9.1 are
randomly arranged. One hook is occupied by a container that is connected to
the smaller pump at left. The tubes are thoroughly tangled.
Karen Cox wanted a hook immediately above each of the infusion pumps so that
it would be clear which medications were running through each of the four pumps
If a device is not appropriate for an engineering class project, an organization
should continue to explore its options. One possibility is to consider networking
with local chambers of commerce or with members of civic organizations such
as the Rotary Club or Optimist Club in order to develop contacts with local
factory engineering managers. Engineering managers are likely to have experience
obtaining custom tool design, fabrication, assembly, and installation in the
local area. Local machine shops (sometimes listed under "Machinery-custom"
in the phone book), metal fabricators, and systems integrators also can help.
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Fabrication is an industrial term generally applied to the building of metal
machines and structures. Fabrication shops and machine shops have overlapping
capabilities, with fabrication shops concentrating on metal forming and welding.
Go to: http://en.wikipedia.org/wiki/Fabrication_(metal).
Assembly is the stage of production in which components are put together into
an end-product appropriate to the process concerned. Go to
A machine shop is a workshop where metal is cut and shaped by machine tools.
A systems integrator is an individual or company capable of making diverse
components work together as a system. The word system usually implies the inclusion
of a computer or microprocessor component to the project. Sources for more
- A Directory of System Integrators in the Medical Industry for Factory
Automation, Process Control, and Instrumentation is available at
- Medical DeviceLink—a Web site associated with the medical device industry
provides a directory of North American Suppliers of Automation and Custom
equipment and Software. Go to http://www.devicelink.com/company98/category/Manufacturing_Equipment_and_Software/AutomationCustom_equipment.html.
- Automation Resources Inc. offers "online resources for industrial
automation, process control & instrumentation" at http://www.automationtechies.com.
- The Control and Information System Integrators Association (CSIA) provides
a search feature that enables users to search for experienced CSIA member
integrators according to industry, application, location, and service. Go
The CSIA also provides a free, two-volume guide to selecting and working with
a systems integrator that covers most aspects of finding the right systems
integrators, and highlights the nuances of navigating a project that otherwise
might be initially overlooked. These are available at:
C. Martin Hinckley's book, Make No Mistake! An Outcome Based Approach to
Mistake-Proofing,7 contains extensive descriptions
of, and supplier information about, sensors and other technologies that are useful
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A Path Forward
The discussion in these nine chapter has introduced the concept of mistake-proofing
and provided a rationale for using mistake-proofing to reduce errors in health
care. It has also delineated a set of concepts, a vocabulary, and tools to
assist organizations in taking action. This book contains 150 examples provided
by the health care industry, as well as examples provided by manufacturing
industries and people in everyday life. Anecdotal evidence indicates that,
after they learn about mistake-proofing, readers are more likely to start noticing
mistake-proofing examples around them and employ mistake-proofing to develop
solutions. Gosbee and Anderson8 found that root
cause analysis (RCA) teams who have been exposed to human factors engineering case
studies often change their focus to "underlying design-related factors,"
such as mistake-proofing, as remedial actions. Initiating this change in focus is
the goal of this publication.
As you complete Failure Modes and Effects
Analyses (FMEAs) and RCAs or witness errors, you will envision new ways
to solve problems and create novel mistake-proofing devices. As these ideas
are implemented as locally developed mistake-proofing devices, please spread
the news of their existence. Submit them as indicated below or publish them
in some other venue so that others can benefit from the solution. Modesty,
minimizing contributions, or assuming that others have thought of a locally
developed solution does not serve the greater good. Some of the best mistake-proofing
will be exceptionally simple and inexpensive. All solutions will be developed
locally by someone before they become off-the-shelf solutions. Be that someone.
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The examples presented here do not by any means represent an exhaustive listing
of devices currently in use. Example contributions are welcome. Contribute
mistake-proofing examples by visiting http://www.mistake-proofing.com and clicking
on "Submit Example." Select the preferred submission method and
add to the database of mistake-proofing examples. Comments on the devices featured
in this book are also welcome.
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1. Godfrey AB, Clapp TG, Nakajo T, et al. Error
proofing database. http://www.tx.ncsu.edu/errorproofing/. Accessed September 2005.
2. Stewart DM, Melnyk SA. Effective process
improvement: developing poka-yoke processes. Production and Inventory Management
3. Tsuda Y. Implications of fool proofing in the
manufacturing process. In: Kuo W, ed. Quality through engineering design. New York:
4. Shingo S. Zero quality control: Source inspection
and the poka-yoke system. New York: Productivity Press; 1985.
5. Chase RB, Stewart DM. Mistake-proofing: designing
errors out. Portland, OR: Productivity Press; 1995.
6. Squire JC. Written communication. Virginia
Military Institute: July 2005.
7. Hinckley CM. Make no mistake. Portland, OR:
Productivity Press: 2001.
8. Gosbee J, Anderson T. Human factors engineering
design demonstrations can enlighten your RCA team. Qual Saf Health
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