1. Chapter 15 Theories From the Biomedical Sciences

2. 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

3. 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

4. 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

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

6. 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

7. 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

8. 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

9. 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.

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

11. 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.

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

13. 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.

14. 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)

15. 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.)

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

17. 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)

18. 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

19. 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.

20. 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

21. 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

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

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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.

29. 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

30. Genetics in Nursing—Example
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31. 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.

32. 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.

33. 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.

34. 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.

35. 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.)

36. 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