Chapter 15

Copyright © 2015 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 15
Theories From the Biomedical
Sciences

Theories From Biomedical Sciences
• Theories from the biomedical sciences (e.g., biology,
medicine, public health, physiology, pharmacology) have
a tremendous impact on nursing practice.
• Many of these theories are so integral to nursing that
they are overlooked
• Not a significant area of nursing research until recently

Theories From Biomedical Sciences—
(cont.)
• The number of biomedical theories and their use in
nursing practice is staggering; examples are:
– Theories of disease causation
• Germ theory (infection/asepsis)
• Natural history of disease
• Web of causation
– Genetic principles/theories
– Pain management

Germ Theory/Principles of Infection
• Proposed by Louis Pasteur in 1858; confirmed by Lister in
mid-1860s
– Postulated that microscopic organisms (germs)
caused diseases
– Critical for developing modern medical care

Germ Theory/Principles of Infection—
(cont.)
• Describes the process that seeks to identify, understand,
and manage infectious diseases

Germ Theory/Principles of Infection—
(cont.)
• Today, theories of infection are widely applied to
prevent infection (e.g., universal precautions; surgical
asepsis)
• Includes search for the causative agent of an infection
and methods of transmission; examples:
– HIV
– SARS
– Creutzfeldt–Jakob disease/bovine spongiform
encephalopathy

Germ Theory/Principles of Infection –
Application
• Education—the first skill taught to nursing students is
hand washing
• Practice—infection prevention and treatment is a
primary component of nursing care in all settings
– Articles—evolution to hand hygiene

Germ Theory/Principles of Infection –
Application—(cont.)
• Research—common subject
– Prevention of infection in hospitalized
cancer patients
– Use of sterile barriers to prevent infection
in central venous catheters

Web of Causation
• Developed by MacMahon and Pugh (1970) as the “chain
of causation”
• Model which attempts to explain disease and disability
caused by multiple factors
– Chronic diseases are not attributable to one or two
factors or causative agents.
– Chronic disease results form the interaction of
multiple factors.

Web of causation.
(Adapted with permission from Friedman, G. D. [1994]. Primer of epidemiology
[4th ed.]. New York: McGraw-Hill.)

Question
Tell whether the following statement is true or false:
The web of causation focuses attention on one or two
primary agents or factors, which lead to a disease state.

Answer
False
Rationale: The web of causation explains or describes the
multiple causes of chronic diseases or health conditions.

Web of Causation—(cont.)
• Implications
– Recognition that many health problems have multiple
causes leads to the recognition that there are rarely
simple solutions to these problems.
– Many points for intervention may be needed.

Natural History of Disease
• Discussed by Leavell and Clark in 1965; two central
tenets:
– Periods in the history of disease
(prepathogenesis, pathogenesis)
– Levels of prevention (primary, secondary,
tertiary)

Natural history of disease.
(Adapted with permission from Leavell, H. R., & Clark, E. G. [1965]. Preventive
medicine for the doctor in his community: An epidemiologic approach [p. 18].
New York: McGraw-Hill.)

Question
The central tenets of the natural history of disease model
are the levels of prevention and:
A.Behavioral or lifestyle intentions
B.Epidemiological bases
C.Human stress reactions
D.Periods in the disease history

Answer
D. Periods in the disease history
Rationale: The Natural History of Disease model linearly
aligns the levels of prevention on the periods of disease
history (prepathogenesis, early pathogenesis, early
disease, advanced disease)

Natural History of Disease—Application
• Practice—much of nursing practice focuses on
prevention of progression of disease from one stage
to the next
– Primary prevention examples—prevention of
obesity, osteoporosis, neural tube defects,
accidents, immunizations
– Secondary prevention examples—mammography
programs, prostate screening efforts
– Tertiary prevention examples—prevention of
subsequent heart attacks through cardiac
rehabilitation, prevention of complications of
diabetes

Genetics
• Although principles of genetics date back to Mendel’s
work in the 1860s, only in the last decade have
significant advances been made.
• The field of genetics has exploded in the last 5 years and
its importance to nursing will continue to grow.
• Almost on a daily basis, there is a new test, disease
component, or new research findings related to genetics.

Human Genome Project
• The Human Genome Project was initiated in 1990 and
completed in 2003.
– Coordinated by the NIH and Department of Energy
– Created a database of the genome structure and
sequence in humans

Human Genome Project—(cont.)
• Project goals were to
– Identify the 20,000 to 25,000 genes in the human
DNA
– Determine the sequences of the 3 billion chemical
base pairs that make up DNA
– Create databases of the information
– Address ethical, legal, and social issues related to
the project

Question
Which of the following is NOT a goal of the Human Genome
Project?
A.Create databases of the information
B.Determine the sequences of the 3 billion chemical base
pairs that make up DNA
C.Identify the 20,000 to 25,000 genes in the human DNA
D.Overcome legal and ethical objections related to genetic
testing and interventions

Answer
D. Overcome legal and ethical objections related to genetic
testing and interventions
Rationale: One of the goals was to address ethical, legal,
and social issues related to the project; it will likely never
be possible to overcome all legal and ethical issues
related to the genome project.

Genetics—Concepts
• DNA is composed of four chemicals (A, T, C, G); the
sequence of DNA is a side-by-side arrangement of
bases along the DNA strand (e.g., ATTCCGGA).
– The order determines the traits of the organism.
– The sequence of the base is repeated millions or
billions of times throughout a genome.
• DNA is arranged into 24 distinct chromosomes—
molecules that range from about 50 million to 250
million pairs.

Genetics—Concepts—(cont.)
• Genome—the complete set of DNA in an organism
– The human genome has 3 billion pairs of bases (a
bacterium contains about 600,000 pairs).
• Gene—the basic physical and functional units of
heredity
– Carries information for the specific sequences of
bases that encode functions to make proteins
– There are about 20,000 to 25,000 genes in humans.
– Genes comprise only about 2% of the genome.
– Functions are unknown for more than 50% of
discovered genes.

Genetics—Concepts—(cont.)
• Proteins—large complex molecules composed of amino
acids; chemical process of the amino acids determine
the following:
– How the protein chains function in the cell
– How the organism looks, metabolism, behavior
– Humans share most of the same protein families as
worms, flies, and plants, but the number of genes
is expanded in humans.
• Gene mutation is the alteration in the coding of the
DNA and results in a change in the protein product.
– Mutations in some genes cause clinical disease due
to absence of the normal protein.

Genetics—Application to Nursing
• There is a vital recognition of the need to enhance
education of nurses regarding genetics.
– There have been several attempts to mandate a
minimal amount of information related to genetics
in curricula.
– Basic understanding of genetics is required by TX
BNE for BSN programs.
– There are a few MSN programs and several
opportunities for doctoral program research in
nursing genetics.

Genetics—Application to Nursing—(cont.)
• Nurses should be aware of when/where to incorporate
genetics into practice.
– Genetic counseling may be appropriate in many
settings.
• OB nursing and pediatric nurses look at genetic
anomalies in infants and may be part of genetic
screening.
• Cancer nurses should be aware of latest data
related to testing for genetic markers.
• Cardiac specialists and community nurses
should be aware of genetic predictors of CHD.

Genetics—Application to Nursing—(cont.)
• Significant research into genetics has been conduced by
nurses and it is a priority area identified by the NINR;
studies include:
– Biologic factors in prevention of type 2 diabetes
– Weight management in women
– Genetics and renal function
– Cystic fibrosis management
– Primary prevention in patients with family history of
CHD

Genetics in Nursing—Example
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1547-

Pain Management
• Pain management has received significant emphasis in
nursing.
• Pain is a complex phenomena with multiple causes,
manifestations, and variable perceptions.
• Pain theories can relate to focus on physiology,
psychology, pharmacology, and other disciplines.

Gate Control Theory
• Proposed in 1965 to explain the relationship between
pain and emotion
• Researchers observed that pain is not merely physiologic
but often has emotional or psychological factors.

Gate Control Theory—(cont.)
• The GCT describes a gating mechanism in the spinal
cord.
– Pain impulses are transmitted from the periphery of
the body by nerve fibers.
– Impulses travel to the dorsal horns of the spinal
cord, specifically to the substantia gelatinosa.
– These cells can inhibit or facilitate pain impulses that
are connected by transmission cells.
– If the transmission cells are not inhibited, the gate is
open and pain impulses ascend to the brain.

Gate Control Theory—(cont.)
• If the activities of the transmission cells are inhibited, the
gate is closed and impulses are less likely to be
conducted to the brain.
• Pain medication has an effect on the gaining mechanism.
– If pain medication is administered before the onset of
pain (before the gate is opened), it will help keep the
gate closed.
– Fewer pain impulses will be allowed to pass through
– The greater the degree of pain impulses, the greater
the pain experience.
• Intervention/management of pain suggests goal of
keeping the gate closed.

Gate control theory. L, large-diameter fibers; S, small-
diameter fibers; SG, substantia gelatinosa; T, transmission.
(Adapted with permission from Watt-Watson, J. H., & Donovan, M. I. [1992]. Pain
management [p. 20]. St. Louis: Mosby.)

Gate Control Theory – Application
• Several recent articles describing application of the GCT
in nursing; examples:
– Several mentioned methods to manage labor pain
– Several mentioned methods to manage
postoperative pain
• Spinal fusion patients
• CABG patients
• Hernia patients

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