Chapter 1 (continued)
Attributes of Mistake-Proofing
Several attributes of mistake-proofing are presented below.
Although this book extols its benefits, mistake-proofing
can encompass liabilities as well as benefits. It is equally
important to know what mistake-proofing cannot do and
which liabilities need to be addressed, as it is to know
what mistake-proofing can do to reduce errors.
Mistake-Proofing is Inexpensive
The cost of mistake-proofing devices is often the fixed
cost of the initial installation plus minor ongoing
calibration and maintenance costs. Shingo's book contains
112 examples.4 He provides the cost (in 1986 U.S.
dollars) of each example. Their distribution is shown in
Table 1.6. The median cost of a device is approximately
$100. Ninety percent of the devices cost $1,000 or less.
Others26,27 implementing mistake-proofing report similar
outcomes. A device's incurred cost per use can be zero, as
it is with the 3.5-inch diskette drive. The cost per use can
also be negative in cases in which the device actually
enables the process to proceed more rapidly than before.
Table 1.6. Implementation cost for Shingo's
(1986 U.S. Dollars)
|Probability ||Cumulative Probability
|$25 < Cost <$100||29.1%||54.6%|
|$100 < Cost <$250||23.6%||78.2%|
|$250 < Cost <$1,000||13.6%||91.8%|
|Cost > $1,000||8.2%||100.0%|
The costs of implementing mistake-proofing in health care
may be greater than the associated costs in manufacturing.
More caution will be required to assess all possible risks of
implementation. In some cases, clinical trials will be
needed to ensure the efficacy of the device. In others,
regulatory approval will be needed. All these steps will add
to the cost.
At this writing, many health care providers are
implementing bar coding, computerized physician order
entry (CPOE), and robotic pharmacies (Figure 1.13).
These are technologically sophisticated examples of
mistake-proofing, which are effective responses to human
error but are very complex and expensive to implement.
They are not typical of the majority of mistake-proofing
approaches, which are based on simplicity and ingenuity.
Bar coding and CPOE are technologically sophisticated
examples of mistake-proofing.
In manufacturing, where data are available, mistake-proofing
has been shown to be very effective. There are
many management tools and techniques available to
manufacturers. However, many manufacturers are unaware
The TRW Company reduced its defect rate from 288
parts per million (ppm) defective to 2 parts per million.29
Federal Mogul had 99.6 percent fewer customer defects
than its nearest competitor and a 60 percent productivity
increase by systematically thinking about the details of
their operation and implementing mistake-proofing.30
DE-STA-CO manufacturing reduced omitted parts from
800 omitted ppm to 10; in all modes, they reduced
omitted parts from 40,000 ppm to 200 ppm and, once
again, productivity increased as a result.31 These are very
good results for manufacturing. They would be
phenomenal results in health care. Patients should be the
recipients of processes that are more reliable than those in
manufacturing. Regrettably, this is not yet the case.1
Mistake-Proofing Can Result in
Substantial Returns on Investment
Even in manufacturing industries, however, there is a low
level of awareness of mistake-proofing as a concept. In an
article published in 1997, Bhote32 stated that 10 to 1,100
to 1, and even 1,000 to 1 returns are possible, but he also
stated that awareness of mistake-proofing was as low as 10
percent and that implementation was "dismal" at 1 percent
Exceedingly high rates of return may seem impossible to
realize, yet Whited33 cites numerous examples. The Dana
Corporation reported employing one device that
eliminated a mode of defect that cost $.5 million dollars a
year. The device, which was conceived, designed, and
fabricated by a production worker in his garage at home,
cost $6.00. That is an 83,333 to 1 rate of return for the
first year. The savings occur each year that the process and
the device remain in place.
A worker at Johnson & Johnson's Ortho-Clinical
Diagnostics Division found a way to use "Post-It® Notes"
to reduce defects and save time that was valued at $75,000
per year. If the "Post-It® Notes" cost $100 per year, then
the return on investment would be 750 to 1. These are
examples of savings for a single device.
Lucent Technologies' Power System Division implemented
3,300 devices over 3 years. Each of these devices
contributed a net savings of approximately $2,545 to their
company's bottom line The median cost of each device
was approximately $100. The economics in medicine are
likely to be at least as compelling. A substantial amount of
mistake-proofing can be done for the cost of settling a few
malpractice suits out of court.
Mistake-proofing Is Not a
It will not obviate the need for other responses to error.
Chapter 2 includes a discussion of how mistake-proofing
relates to other common patient safety initiatives.
Mistake-Proofing Is Not Rocket
It is detail-oriented and requires cleverness and careful
thought, but once implementation has been completed,
hindsight bias will render the solution obvious. Chapter 3
presents tools and techniques that help to create mistake-proofing
devices and analyze their impact on the process.
Mistake-Proofing Is Not a
It cannot eliminate all errors and failures from a process.
Perrow34 points out that no scheme can succeed in
preventing every event in complex, tightly-linked systems.
He argues that multiple failures in complex, tightly-linked
systems will lead to unexpected and often
incomprehensible events. Observers of these events might
comment in hindsight, "Who would have ever thought
that those failures could combine to lead to this?" Perrow's
findings apply to mistake-proofing as they do to any other
technique. Mistake-proofing will not work to block events
that cannot be anticipated. Usually, a good understanding
of the cause-and-effect relationship is required in order to
design effective mistake-proofing devices. Therefore, the
unanticipated events that arise from complex, tightly-linked
systems cannot be mitigated using mistake-proofing.
Although health care is a complex, tightly-linked system,
many potential adverse events can be anticipated. In fact,
some of the more common errors occur in hospitals daily
or hourly. When a patient is misidentified, a specimen is
mislabeled, or a wrong-site operation occurs, people
familiar with patient safety will not say, "Wow. Who
would ever have believed that could happen?" It is in this
domain of anticipated events that mistake-proofing is
Mistake-Proofing Is Not New
It has been practiced throughout history and is based on
simplicity and ingenuity. Mistake-proofing solutions are
often viewed post hoc as "common sense." Senders and
Senders35 provide an example of mistake-proofing, the
dispensing of medications in the mid-1800s (Figure 1.14).
Bottles of poison are variously identified by their
rectangular shape, blue-colored glass, or the addition of
small spikes to make an impression on inattentive
pharmacists. Most organizations will find that examples of
mistake-proofing already exist in their processes. The
implementation of mistake-proofing, then, is not entirely
new but represents a refocusing of attention on certain
design issues in the process.
Return to Contents
Creating Simplicity Is Not
In hindsight, mistake-proofing devices seem simple and
obvious. A good device will lead you to wonder why no
one thought of it before. However, creating simple,
effective, mistake-proofing devices is a very challenging
task. Significant effort should be devoted to the design
process. Organizations should seek out and find multiple
approaches to the problem before proceeding with the
implementation of a solution.
This book is intended to help organizations design
mistake-proofing devices. Its goal is to provide a process
and a vocabulary for thinking about patient safety and
error reduction. It is hoped that this book will also help
reduce the amount of creativity needed to devise novel
approaches to eliminating problems and reducing risk.
Each organization's mistake-proofing needs may be
different, depending on the differences in their processes.
Consequently, some mistake-proofing solutions will
require new, custom-made devices designed specifically for
a given application. Other devices could be off-the-shelf
solutions. Even off-the-shelf devices will need careful
analysis—an analysis that will require substantial process
understanding-in the light of the often subtly
idiosyncratic nature of their own processes.
Chapter 2 reviews current patient safety tools and
proposes a flowchart view of how existing tools inform the
process of mistake-proofing device design or selection.
Existing tools provide the foundation of process
understanding that enable us to make sense of events and
errors, which is vital to effective mistake-proofing.
Mistake-proofing cannot be effective without a sound
understanding of what happens in the process and why.
Chapter 3 proposes a new use for an existing tool and
combines it with other tools to facilitate mistake-proofing
efforts. Chapter 4 is devoted to discussing important
design issues, caveats, and limitations of mistake-proofing.
Chapters 5, 6, 7, and 8 provide examples of mistake-proofing
in health care. Chapter 9 describes a path
forward and suggests resources to help make mistake-proofing
Return to Contents
Implementing Mistake-Proofing in Health Care
Implementing mistake-proofing in medical environments
will probably be more challenging and difficult than
implementing the same techniques in manufacturing. An
unranked list of opportunities and difficulties is provided
in Table 1.7. The difficulties are not provided as excuses or
reasons why mistake-proofing should not be implemented
but rather as guides to what can be expected as
implementation progresses. The impact of these concerns
can be mitigated by early acknowledgment of their effects
on the process.
Table 1.7. Comparison of medical mistake-proofing applications with those in other industries
|1. Legal liability and discoverability (need for anonymity?)
|2. Lack of shared examples
|3. Careful assessment of down-side risk
|4. Culture of depending on individuals, not on systems
|5. Processes that depend on individuals, not on systems: lack of consistent process
|6. Resource shortages
|7. Medical applications that focus more on information counter-measures
|8. Low barriers to diffusion
|9. Substantial buying power
Legal Liability and Discoverability
Telling quality improvement stories requires great care.
Claiming great improvements could implicitly reveal
previous shortcomings. In claiming the "after," one must
own up to the "before." This is not a significant concern
in manufacturing applications because the problems are
rarely safety related. Disgruntled customers simply get
their money back or receive a replacement product.
Remedies for poor quality in medicine are not as easily
Mistake-proofing devices are physical evidence that actions
have been taken to ensure patient safety. Although this
book contains only examples of good practices, many of
its contributors prefer to remain anonymous. Risk
managers and medical system lawyers differ widely in their
levels of concern about disclosing mistake-proofing
devices. For this book, the range of concerns included
individuals who were proud of their efforts and willing to
receive all credit due them to those who required
significant assurances of anonymity.
Concerns with the litigious environment surrounding
health care will remain an impediment to mistake-proofing
implementation for some time to come. In
addition to existing channels like the Agency for
Healthcare Research and Quality's (AHRQ) Web M&M
(Morbidity and Mortality) and the National Patient Safety
Foundation's (NPSF) LISTSERV™, more options for "safe"
(perhaps anonymous) dialogue and information sharing
should be sought.
Lack of Shared Examples
Manufacturing benefits from a set of four resources4,9-11
with 702 published examples. These examples provide a
large set of existing solutions and approaches to problems;
solutions that can stimulate thinking about additional
approaches. Until now, there was no comparable set of
examples of mistake-proofing in medicine. This book
provides a starting place for sharing medical examples. It is
not comprehensive. There are many more examples to
collect for this ongoing effort.
Add to the body of knowledge in medical mistake-proofing:
Submit any examples that you know of that do
not appear in this book. Submissions can be made
(anonymously, if desired) at http://www.mistake-proofing.com/medical.
Careful Assessment of Down-Side Risk
In manufacturing, one can afford to be more cavalier in
trying new things. In fact, Hirano36 proposes the following
heuristic: if a device is found to have greater than a 50
percent chance of success for mistake-proofing, then it
should be tried immediately. The parts can be discarded if
the experiment does not work. In health care, this
approach is often unacceptable, given the requirement of a
careful assessment of the patient safety risk of each new
mistake-proofing device. Where there is risk of patient
harm, careful analysis and clinical trials may be needed.
However, experimenting with a device theoreticallyb will
not make the patient "worse off " in cases in which current
controls depend entirely on human attentiveness for their
accuracy. If the mistake-proofing device is also a medical
device, it must adhere to the same rigorous regulatory
approval process required for any other device.
b. Practically, experimenting with a device could reduce patient safety if users depend on the device instead of exercising normal
levels of care and attentiveness. Go to the discussion of Risk
Homeostasis in Chapter 4 for more information.
A Culture of Depending on
People, Not on Systems
The traditional approach within medicine has been to
stress the responsibility of the individual and to encourage
the belief that the way to eliminate adverse events is to get
individual clinicians to perfect their practices. This
simplistic approach not only fails to address the important
and complex system factors that contribute to the
occurrence of adverse events but also perpetuates a myth
of infallibility that is a disservice to clinicians and their
The reasons are found in the culture of medical
practice... Physicians are socialized in medical school
and residency to strive for error-free practice...
Physicians are expected to function without error, an
expectation that physicians translate into the need to be
The medical culture makes implementing mistake-proofing
more difficult because health care professionals
are accustomed to looking for solutions involving
"knowledge in the head." Getting them to consider
"knowledge in the world" can be very challenging. Some
aspects of the implementation may challenge long-held
assumptions, beliefs, and values associated with behavior
Barry, Murcko, and Brubaker39 discuss this issue regarding
medical software interfaces.
The complex displays allow the specialists to apply
their mastery and preserve the special knowledge they
have acquired. The experts do not see a need for any
help, and they do not want any help. In fields other
than health care, giving experts help, even if they do
not want it, is found to reduce error rates.
Perhaps this is the case in the health care field, too:
even though experts do not want help, maybe they
could use a little anyway, for the good of the cause.
Computer displays should make doing the right thing
easier than doing the wrong thing... They should
make it obvious, immediately, when the wrong thing
has been done... All these ideas are not only common
sense, they are poka-yoke.
Processes that Depend on People,
Not on Systems
In medicine, the dependence on the individual is cultural,
and it is exhibited in processes managed within that
culture. As a result, medical processes are often customized
by each practitioner of the art. Noted doctors and patient
safety advocates have questioned whether there are
processes in medicine at all. The lack of consistent
processes will make implementation of mistake-proofing
more difficult in medicine than in manufacturing.
Inconsistent processes are more difficult to mistake-proof
because there are fewer predictable elements that can be
used to check the process.
Ideally, changes will liberate additional resources, but
adequate resources are required to make those changes
possible. Adequate resources and staffing levels enable
process improvement. A shortage of nurses, other staff, or
resources will generally make mistake-proofing more
difficult. Go to the section of Chapter 4, titled, "Spending
Too Much or Not Enough" for additional information
about the ironic situations that can prevent organizations
from allocating resources to process improvement efforts.
More Focus on Information
Mistake-proofing in manufacturing has primarily focused
on physical, sequencing, and grouping and counting
mistake-proofing devices. More information-enhancement
devices should be anticipated as mistake-proofing is more
widely implemented in service industries. Health care
services involve numerous "matching" tasks. These are
tasks in which specific medications, medical devices,
processes, and procedures are matched to specific,
individual patients during specific time intervals. These
tasks require the availability of substantial amounts of
usable, accurate information. Mistake-proofing devices for
information enhancement are needed in these
circumstances. Increasing the proportion of theses devices
will be challenging. There is a need for the invention and
documentation of newer and better examples of these
Low Barriers to Diffusion
Health care enjoys an advantage over manufacturing.
Because much of health care competition is geographically
based, new devices can be shared with less impact on
competitive advantage than there would be in the
manufacturing sector. Consequently, mistake-proofing
devices that would be cloaked in secrecy to foster a
competitive advantage in manufacturing are more likely to
be shared in the health care environment.
Substantial Buying Power
Vendors have already begun to use patient safety
improvements as a marketing tool. Hospital systems and
large payers possess the buying power to specify safer
designs and to seek out vendors willing to provide them.
Health care providers should employ a practice that
Leenders and Blenkhorn40 called "reverse-marketing."
Their concept is to reverse the roles of supplier and buyer
so that buyers are marketing ideas to their suppliers.
Traditionally, the supplier tries to persuade the buyer to
buy, but in reverse marketing the buyer tries to persuade
the supplier to supply. That is, the buyer exerts influence
on suppliers to encourage them to produce what the buyer
wants. Leenders and Blenkhorn38 argue that purchasing
managers are mistaken in their impression that they have
most of the power in the transaction because they make
the final purchasing decision. The authors make a
convincing case that suppliers, by having control over
which product configurations are offered, have much
more power to shape transactions, and that purchasers
should attempt to take some of that power back by trying
to influence what is offered.
The British National Health
Service is making an effort to shape the product offerings
that affect them by seeking improved labeling of
medications using this type of proactive approach (Go to
Chapter 8, Example 8.29). Larger medical systems, for-profit
hospital chains, government-run hospital systems,
and payer groups could be very persuasive in convincing
suppliers to change the designs of equipment, devices, and
Return to Contents
Mistake-proofing involves designing changes into the
physical aspects of the design of processes. Design changes
can prevent mistakes by simplifying or clarifying the work
environment, making mistakes less likely. Mistakes can
also be prevented by inspecting the source or cause of
errors so that the effect cannot occur. When this is not
possible, mistakes should be detected rapidly, prior to
causing harm, or while remediation is still relatively easy.
If the mistake itself cannot be prevented or effectively
detected, then preventing the influence of mistakes (the
harm) may be warranted. These mistake-proofing
techniques should be applied to actions taken by patients
and their loved ones as well as to the actions of health care
Changing the design of health care processes and creating
mistake-proofing devices is not a simple task. Careful
deliberation and analysis will be required. In some ways,
implementing mistake-proofing will be more difficult in
health care environments than in other industries. There
are, however, efforts to lay the foundation for successful
implementation already underway. Chapter 2 describes
Return to Contents
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