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978-1-107-03719-9 - Biomedical Engineering: Bridging Medicine and Technology

W. Mark Saltzman
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1 Introduction: What Is Biomedical

Engineering?

LEARNING OBJECTIVES
After reading this chapter, you should:

n Be familiar with how changes in medicine have enhanced life span and quality of life.
n Understand a few examples of the role of engineering in medical diagnosis, treatment,
and rehabilitation.
n Have developed your own definition of biomedical engineering.
n Understand some of the subdisciplines of biomedical engineering.
n Understand the relationship between the study of biomedical engineering and the study
of human physiology.
n Be familiar with the structure of this book, and have developed a plan for using it that
fits your needs.

1.1 Prelude

The practice of medicine has changed dramatically since you were born. Consider
a few of these changes:

• Vaccines are now available for chicken pox and human papilloma virus;
• Microarrays allow rapid patient-specific testing for mutations in genes control-
ling metabolism of potentially toxic drugs;
• Inexpensive contact lenses provide clear vision;
• Prosthetic legs allowed a double-amputee to run in the Olympics;
• Ultrasound imaging follows the progress of pregnancy with ever greater
precision;
• Stem cells in human cord blood have been used to treat dozens of diseases in
donors, or their siblings;
• An iPhone app driving a bionic pancreas offers better control of diabetes.
For your parents, the changes have been even more sweeping. Overall life
expectancy—that is, the span of years that people born in a given year are

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2 Biomedical Engineering: Bridging Medicine and Technology

Figure 1.1
Human life expectancy.
Human life expectancy has
increased dramatically in the
past 200 years.

expected to live—increased from 50 in 1900 to almost 80 by 2010 (Figure 1.1).

You can expect to live 30 years longer than your great-grandparents; you can also
expect to be healthier and more active during all the years of your life.
How has this happened? One answer is obvious. People are living longer
because they are not dying in situations that were previously fatal, such as
childbirth and bacterial infections. Biomedical engineering is a major factor in this
extension of life and improvement of health. Biomedical engineers have contrib-
uted to every field of medicine—from radiology to obstetrics to cancer treatment
to control of diabetes. The next few paragraphs illustrate the far-reaching contribu-
tions of biomedical engineers with examples from emergency medicine.
Loss of life in accidents and trauma is a major cause of death and disability
around the world. In the United States, it is overwhelmingly the leading cause of
death among people of college age, and it is ranked fifth among causes of death for
all ages (1). Automobile accidents account for many of these deaths: 32,367
people were killed in automobile accidents in the United States in 2011, which
was the lowest number in 62 years. Victims of trauma often have internal injuries,
which are life threatening, but not easy to diagnose by visual observation. Many
accident victims are rushed to emergency rooms for treatment, and actions per-
formed in the first few minutes after arrival can often mean the difference between
life and death. Emergency room treatment has improved enormously over the past
few decades, chiefly due to advances in the technology of looking inside of people
quickly and accurately (Figure 1.2). Ultrasound imaging, which can provide
pictures of internal bleeding within seconds, has replaced exploratory surgery
and other slower, more invasive approaches for localization of internal injuries.
Old ultrasound imaging machines weighed hundreds of pounds, but new instru-
ments are smaller and lighter—some weighing only a few pounds, making it

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3 Introduction: What Is Biomedical Engineering?

Figure 1.2 possible to get them to the patient

Some biomedical engineering faster. Other imaging technologies
technologies that one might
I have also improved: Helical computed
encounter on a visit to an tomography (CT) scanners produce
emergency room.
A. An electrocardiogram
rapid three-dimensional internal
measures the electrical images of the whole body, and new
II
activity of the heart through magnetic resonance imaging (MRI)
electrodes attached at
techniques can reveal the chemistry,
defined locations on the
body surface. not just the shape, of internal struc-
B. Syringe and needle for III tures. As a result of faster and better
administration of drugs. diagnosis of internal injuries, more
C. Chest x-rays are used to
screen for lung diseases
accident victims are saved today.
such as tuberculosis. aVR Already, many emergency medi-
D. Defibrillator for restoring cine providers are using ultrasound
normal heart rhythm. Photo imagers that are small enough to be
courtesy of Dr. Yury
Masloboev. aVL carried in a pocket; these devices may
E. Laryngoscope for intubation someday be inexpensive enough for
to provide breathing. Photo every physician to own, like a stetho-
courtesy of Abinoam
aVF
scope is today. Reduction in size and
Praxedes Marques Junior.
cost will surely save the lives of more
accident victims. A pill-sized sensor is
already available that patients can swallow; it continuously reports internal tem-
perature as it passes through the intestinal tract. In the future, similar devices will
probably be used to report other internal conditions such as sites of bleeding or
abnormal cells. Further in the future, these small devices will be guided to specific
locations in the body, where they can initiate repair of disease that is deep within
the body.
These trends in emergency medicine are not unique. Innovations produced by
biomedical engineers are saving lives once lost to kidney failure, improving
eyesight lost to disease and aging, and producing artificial hips, knees, and hearts.
If you want to be a part of this story—or a part of similar stories that are
changing the conduct of medicine in operating rooms, doctors’ offices, emergency
vehicles, and homes—then you want to be a biomedical engineer. This book will
introduce you to the field of biomedical engineering and show how your know-
ledge of math, chemistry, physics, and biology can be used to understand how the
human body works. It will show you how biomedical engineers develop new
methods to diagnose problems with the human body and new approaches to treat
disease efficiently and inexpensively. This book will also help you predict how
biomedical engineering and medicine will change over the next years, and point
you in some directions that you can pursue to be part of this future. Biomedical

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4 Biomedical Engineering: Bridging Medicine and Technology

Figure 1.2 B
A
(cont.)

C D

engineering has been performed under different titles throughout history

(Box 1.1); this book will help put the developments of the field into perspective,
so you can focus on how biomedical engineers will contribute to the future.

1.2 Engineering in modern medicine

Our experience of the world is shaped by engineering and technology. Because of

the work of engineers, we can move easily from place to place, communicate with
people at distant sites (even on the moon!), live and work in buildings that are safe
from natural elements, and obtain affordable and diverse foods. It is widely (but
not universally) accepted that the quality of life on our planet has improved as a
result of the proliferation of technology that occurred during the 20th century.

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5 Introduction: What Is Biomedical Engineering?

BOX 1.1 Too many names?

As you read about the subject of biomedical engineering, you will encounter a variety of names that
sound similar: bioengineering, biological engineering, biotechnology, biosystems engineering,
bioprocess engineering, biomolecular engineering, and biochemical engineering. Some of the differ-
ences between these names are important, but unfortunately the terminology is not used consistently.
Therefore, students of biomedical engineering need to approach the terminology with care (and
without assuming that the person using the terminology has the same definition that they do!).
Biomedical engineering and bioengineering are
often used interchangeably [e.g., see ref. (2)]. This is
certainly true in the naming of academic departments
at universities. Some departments are called
Department of Biomedical Engineering and others
Department of Bioengineering, but in most cases, the
educational mission and research programs associated
with these departments are similar. Still, it is wise for
prospective students to look closely at the classes that
are offered at each university and to decide if the
emphasis of the department is the right one for them.
Some of the terms represent subsets of the larger
discipline of biomedical engineering. Biomolecular
engineering, for example, is now used to describe the
contributions of chemical engineering to the larger
field of biomedical engineering. In that sense, bio-
chemical engineering and bioprocess engineering,
which have historically been used to indicate the
use of chemical engineering tools in the development
of industrial processing methods for biological systems, are now embraced by the larger
subdiscipline of biomolecular engineering. One could argue that all of these are subsets of the
larger field of bioengineering or biomedical engineering.
Biotechnology is a trickier term to characterize because it has been used in a variety of
different contexts over the past few decades. To many people, biotechnology is the end result
of DNA manipulation: for example, transgenic animals, recombinant proteins, and gene therapy.
Some common definitions are “the application of the principles of engineering and technology to
the life sciences”; “the application of science and engineering to the direct or indirect use of
living organisms, or parts or products of living organisms, in their natural or modified forms”; or
“the use of biological processes to solve problems or make useful products.” Again, one could
argue that these definitions are equivalent to biomedical engineering. Even the technologies most
commonly associated with biotechnology (e.g., production of recombinant proteins as pharma-
ceuticals) are examples of biomedical engineering. They are treated as such in this textbook, and
are discussed in Chapters 13 and 14.

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6 Biomedical Engineering: Bridging Medicine and Technology

There is little doubt that the presence of technology creates constraints on the way
that we live, and that the daily choices we make are shaped by the technologies
that have infiltrated widely (think about the ways that television, computers,
airplanes, cell phones, and ATMs have influenced your progress through this past
day). Choices that individuals make, and even historical trajectories, will be
influenced by future technologies such as nanomachines, efficient fuel cells,
methods to clean water, and tiny global positioning devices. It is the work of
engineers to make technology possible, and then to make that technology reliable
and inexpensive enough to influence people throughout the world.
Medical technology is one of the most visible aspects of the modern world; it is
impossible to avoid and uniquely compelling. People from all walks of life are
eager to hear about new machines, new medicines, and new devices that will
uncover hidden disease, treat previously untreatable ailments, and mend weary or
broken organs. Evidence of this high interest is everywhere; for example, new
medical technologies appear routinely on the covers of magazines and newspapers
such as Newsweek and The New York Times: for example, in the first half of 2014,
Time magazine ran cover stories on advances in the technology for saving
prematurely-born infants and the information technology behind HealthCare.
gov. We know that modern medicine is built on steady progress in science, but
it is just as heavily dependent on innovations in engineering. Engineers are
the ones who transfer scientific knowledge into useful products, devices,
and methods; therefore, progress in biomedical engineering is arguably more
central to our experience of modern medicine than are advances in science. Some
of the most fascinating stories of the 20th century involved the development of
new medical technologies (Figure 1.3). Whole-organ transplantation, such as the
first heart transplant in 1967, could not occur until there were machines to sustain
life during the operation, tools for the surgeons to operate with and repair the
wounds they created, and methods for preserving organs during transport. Thou-
sands of transplants are performed annually in the United States today, but the
need for organs far exceeds the supply. Biomedical engineers have been working
for many decades to create an artificial heart, and there is no doubt that this work
will continue until it is successful (see Chapter 15). Clinical testing of the Salk
polio vaccine, in which millions of doses were administered to children, could not
have happened without the engineering methods to cheaply produce the vaccine in
large quantity (see Chapter 14). The Human Genome Project would have not been
possible without automated machines for deoxyribonucleic acid (DNA)
sequencing: Thanks to the latest advances in technology, an individual’s genome
can now be sequenced for ~$1,000.
Medical technology has also invaded our homes in surprising and influential
ways. Every home has a thermometer, specially designed to permit the recording

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A B

C D

Figure 1.3 Examples of new technology that permitted medical advances. A. Heart–lung machine that permits heart transplantation and
surgery. Photo courtesy of National Institutes of Health. B. Jet airplanes are used for rapid transport of a preserved organ
to a distant operating room. C. An injector for vaccine delivery. Photo courtesy of The Centers For Disease Control and Prevention.
D. DNA microarrays can be used to measure the expression of genes in cells and tissues. Photo courtesy of the W.M. Keck
Foundation at Yale University. (See color plate.)

of body temperature. But we can now also test for pregnancy at home, so that one
of the most life-changing medical discoveries can be done in privacy. Blood
glucose tests, which are essential for proper treatment of diabetes, have advanced
rapidly and now are commonly done at home. Your home can be equipped to be a
screening center for high blood pressure, high cholesterol, glucose monitoring,
levels of certain viruses in the blood, and ovulation prediction.
In addition, medical technologies have entered our bodies. Many people now
elect to use contact lenses instead of eyeglasses; this change has resulted from the
development of materials that can remain in contact with the eye for extended
periods without causing damage. Artificial joints and limbs are common, as are
artificial heart valves; synthetic components, usually metals and polymers, are
fashioned into implantable devices that can replace the function of the human
skeleton. As an example, over 700,000 total knee replacements and over 300,000
total hip replacements are performed in the USA each year (National Hospital
Discharge Survey: 2010). We are not yet able to reanimate dead tissue (as Shelley
predicted in Frankenstein), but we are close to the technology required for a
6 million dollar man.

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This book supplies an introduction to biomedical engineering, the most rapidly

growing of the engineering disciplines. Biomedical engineers invent, design, and
build new technologies for diagnosis, treatment, and study rehabilitation of human
disease. Usually, engineers work as a part of a team including engineers, scientists,
and physicians. The role of the engineer in these teams is essential. It is the
engineer who is responsible for converting new knowledge into a useful form.

1.3 What is biomedical engineering?

New students to the field of biomedical engineering ask versions of this question:
“What is biomedical engineering?” Often, they ask the question directly but, just
as often, they ask it in indirect and interesting ways. Some forms of this question
I have heard in the past few years are:

• Do biomedical engineers all work in hospitals?

• Do you need to have an MD degree to be a biomedical engineer?
• How can I learn enough biology to understand biomedical engineering and
enough engineering to be a real engineer?
• Is biomedical engineering the same as genetic engineering?
• How much of biomedical engineering is biology, chemistry, physics, and
mathematics?
Some versions of the question are easy to answer. For example, most biomedical
engineers do not work in hospitals and do not hold MD degrees. Other questions
can inspire answers that take up whole books (such as this book), and still be
incomplete. All of the chapters in this book are designed to address these questions
from different perspectives. In this introduction, the overall question is examined
from several different angles.

1.3.1 We can learn something about biomedical engineering

from standard definitions

Our working definition of biomedical engineering can start in an obvious place.

According to the Merriam-Webster Dictionary:
engineering noun: a) the application of science and mathematics by which the properties of
matter and the sources of energy in nature are made useful to people; b) the design and
manufacture of complex products.

Biomedical engineering is engineering that is applied to human health. Because

human health is multifaceted—involving not only our physical bodies but also the

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Figure 1.4 Chapter 1

Introduction
Organization of this book.

Chapter 2 Chapter 3 Chapter 4 Chapter 5

Biomolecules Nucleic acids Proteins Cellular Principles

Molecular and Cellular Principles

Chapter 6 Chapter 7 Chapter 9

Chapter 8
Communication Respiration and Removal of
Circulation
Systems Digestion Molecules

Physiological Principles

Chapter 13
Biomolecular Chapter 15 Chapter 16
Chapter 10 Chapter 11 Chapter 12
Engineering I Biomaterials and Biomedical Eng
Biomechanics Bioinstrumentation Bioimaging
Artificial Organs and Cancer
Chapter 14
Biomolecular
Engineering II
Biomedical Engineering

things that we put in our bodies (such as foods, pharmaceuticals, and medical
devices) and the things that we put on our bodies (such as protective clothing and
contact lenses)—biomedical engineers are interested in a wide range of problems.
The breadth of modern biomedical engineering is reflected in the table of contents
for this book (shown in diagrammatic form in Figure 1.4).
The work of engineers is often hidden from view of the general public,
occurring in laboratories, office buildings, construction sites, pilot plants, and
testing facilities. This is true for biomedical engineering as well as civil engineer-
ing and other engineering disciplines. Although the work might be hidden, the end
result is often visible and important (e.g., the Brooklyn Bridge or the artificial
heart; see Figure 1.5). Because of this, society has huge expectations for engineers,
and engineers have large goals for themselves.
The importance of engineers to human progress is worthy of celebration.
Consider this quote about the role of engineers from the president of the American
Society of Civil Engineers, Robert Moore. Mr. Moore, in a speech to the society in
May 1902, said [from ref. (3)]:

And in the future, even more than in the present, will the secrets of power be in his keeping,
and more and more will he be a leader and benefactor of men. That his place in the esteem of
his fellows and of the world will keep pace with his growing capacity and widening
achievement is as certain as that effect follow cause.

Mr. Moore was speaking in the shadow of incredible engineering achievements:

The work of engineers to build bridges over large spans of water changed the flow
of society, for example. The substance of this quote—although not its selection of

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Figure 1.5 A B
Examples of engineering on
the heroic scale.
A. Brooklyn Bridge (opened
May 24,1883).
B. AbioCor™ artificial heart
(reprinted with permission
from Jewish Hospital & St.
Mary’s HealthCare and the
University of Louisville).

pronouns – is relevant today. Engineers of today have ambitious visions for their
profession, and they are still called upon to be worthy inheritors of the engineering
tradition to do good works. Imagine the confidence in your profession that is
required to suggest that you can build a machine to replace the human heart, which
is one of the most durable, reliable, and complex of machines. As we will see in
Chapters 13 and 15, the creation of reliable replacement tissues and organs is now
achievable. The success of the Abiomed artificial heart (called AbioCor™,
Figure 1.5, which was approved by the FDA in September of 2006), is an example
of progress in this heroic effort.
The following is a simple definition of engineering: Engineering is the art of
making practical application of the knowledge gaining in science (3). Engineering
is a creative discipline (like sculpture, poetry, and dance), but the end result is
often intended to be durable, useful, abundant, and safe. Engineering art is not
produced for museums, but intended to infiltrate the world.
Technology is a broader and more comprehensive term than engineering;
in general, technology is the end result of a practical application of knowledge
in a particular area. Anyone can produce technology. Engineers are especially
important in the development of technology, because their training is focused
on providing the knowledge and tools needed to produce technology.

1.3.2 Biomedical engineers seek to understand human physiology

and to build devices to improve or repair it

Other textbooks and review articles have described the origins of biomedical
engineering, which can be identified even in ancient sources (2). Rather than
reviewing this history in detail, we instead offer a schematic, speculative view of

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