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Chapter 21
Respiratory Tract Infections,
Neoplasia, and
Childhood Disorders
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Upper Respiratory
Viruses in Adults
• Common cold
• Rhinosinusitis
• Influenza
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The Common Cold
• Rhinoviruses
– Occur in early fall and late spring in
persons between ages 5 and 40
• Parainfluenza viruses
– Occur in children younger than 3
• Respiratory syncytial virus
– Occurs in winter and spring in children
younger than 3
• Coronaviruses and adenoviruses
– Occur in winter and spring
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Rhinosinusitis (Sinusitis)
• Infection or allergy
obstructs sinus drainage
• Acute: facial pain,
headache, purulent nasal
discharge, decreased
sense of smell, fever
• Chronic: nasal
obstruction, fullness in
the ears, postnasal drip,
hoarseness, chronic
cough, loss of taste and
smell, unpleasant breath,
headache
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Influenza
• In the United States, approximately 36,000 persons
die each year of influenza-related illness
• Transmission is by aerosol (three or more particles)
or direct contact
• Upper respiratory infection (rhinotracheitis)
– Like a common cold with profound malaise
• Viral pneumonia
– Fever, tachypnea, tachycardia, cyanosis,
hypotension
• Respiratory viral infection followed by a bacterial
infection
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Question
For which viruses is a 2-year-old most at risk?
a. Rhinoviruses
b. Parainfluenza viruses
c. Respiratory syncytial virus (RSV)
d. All of the above
e. b and c
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Answer
d. b and c
Rationale: Slightly older children (> 5 y) are at risk for
rhinoviral infections. Children under the age of 3 are at
risk of infection from both parainfluenza viruses and
RSV.
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Mechanism of Viral Infection and Treatment
amantadine,
rimantadine
zanamivir,
oseltamivir
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Pneumonia—Inflammation of Alveoli and
Bronchioles
• Typical: bacteria in the alveoli
– Lobar: affect an entire lobe of the lung
– Bronchopneumonia: patchy distribution over
more than one lobe
• Atypical
– Viral and mycoplasma infections of alveolar
septum or interstitium
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Onset of Pneumonia
Infection
• Signs of systemic
inflammation
– Malaise
Inflammation
Serous exudate
– Chills and fever
Congestion,
productive
cough
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serous exudate
fibrous exudate:
RED
HEPATINIZATION
consolidation
• Blood-tinged sputum
• Pleuritic pain
WBCs denature
hemoglobin:
GRAY
HEPATINIZATION
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If WBCs Overcome the Infection
WBCs denature
hemoglobin:
GRAY
HEPATINIZATION
WBCs destroy fibrous
proteins and liquefy
exudate: it is reabsorbed
into the circulation
resolution
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Question
Tell whether the following statement is true or false.
In the progression of pneumonia, serous exudate develops
before fibrous exudate.
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Answer
True
Rationale: Serous exudate develops (just after
inflammation) before fibrous exudate, and is
characterized by a congested, productive cough. If the
pneumonia does not resolve at this stage, fibrous
exudate develops, and the patient will experience
pleuritic pain (worse when taking a deep breath or
coughing) and may expectorate blood-tinged sputum.
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Tuberculosis
• World’s foremost cause of death from a single
infectious agent
• Causes 26% of avoidable deaths in developing
countries
• Drug-resistant forms
• Mycobacterium tuberculosis hominis
– Aerobic
– Protective waxy capsule
– Can stay alive in “suspended animation”
for years
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Initial TB Infection
• Macrophages begin a
cell-mediated immune
response
• Takes 3–6 weeks to
develop positive TB test
• Results in a
granulomatous lesion
or Ghon focus
containing
– Macrophages
– T cells
TB bacteria
inhaled
ingested by
macrophages
in lungs
macrophages
present them
to T cells
activated
T cells
kill
bacteria
– Inactive TB bacteria
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activated T cells
stimulate
macrophages to
kill bacteria more
efficiently
Ghon complex
• Nodules in lung tissue
and lymph nodes
• Caseous necrosis
inside nodules
• Calcium may deposit
in the fatty area of
necrosis
• Visible on x-rays
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Discussion
Someone in your class has a positive TB test.
Question:
• What does this mean?
• Are you at risk of infection?
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Primary TB
usually
isolated in
Ghon foci
bacteria
are
inactive
not
contagious
primary
TB
if immune response is
inadequate, bacteria
multiply in the lungs
progressive primary TB
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Miliary TB
• Miliary TB lesions
look like grains
of millet in the
tissues
• Meat inspection
was introduced
to keep them out
of the food
supply
progressive primary TB
signs of
pneumonia
bacteria in
sputum and
exhaled
droplets
• Pasteurization of
milk was
introduced to
keep TB out of
the milk supply
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bacteria may
erode blood
vessels and
spread through
the body
MILIARY
TB
Secondary TB
• Reinfection from inhaled droplet nuclei
• Reactivation of a previously healed primary lesion
• Immediate cell-mediated response walls off
infection in airways
• Bacteria damage tissues in the airways, creating
cavities
• Signs of chronic pneumonia: gradual destruction
of lung tissue
• “Consumption”: eventually fatal if untreated
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Question
Which type of TB may be reactivated if the patient
becomes immunocompromised?
a. Primary
b. Latent
c. Miliary
d. Secondary
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Answer
d. Secondary
Rationale: Secondary TB, often referred to as reactivation
or reinfection TB, may occur if patients are reexposed to
TB bacilli (after a primary infection) or if they become
immunocompromised (they are unable to contain the
infection).
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Cavitary Tuberculosis
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Lung Cancer
• Bronchogenic carcinoma
– Arises from epithelial cells lining the lungs
– Small-cell lung cancer
– Non–small-cell lung cancer
º Large-cell carcinoma
º Squamous cell
º Adenocarcinoma
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Manifestations of Lung Cancer
• Changes in organ function (organ
damage, inflammation, and failure)
• Local effects of tumors (e.g., compression
of nerves or veins, gastrointestinal
obstruction)
• Ectopic hormones secreted by tumor cells
(paraneoplastic disorders)
• Nonspecific signs of tissue breakdown
(e.g., protein wasting, bone breakdown)
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Respiratory Distress Syndrome
• Lack of surfactant; infants
are not strong enough to
inflate their alveoli
• Protein-rich fluid leaks into
the alveoli and further
blocks oxygen uptake
• Treatment with mechanical
ventilation may cause
bronchopulmonary
dysplasia and chronic
respiratory insufficiency
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Question
Tell whether the following statement is true or false.
Premature infants are at greater risk of developing
respiratory distress syndrome (RDS) than term infants.
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Answer
True
Rationale: RDS occurs due to a lack of surfactant in the
alveoli (the surfactant is produced by alveolar cells, and
keeps them inflated). Surfactant is typically produced
from week 28 (gestational age) through term (40–42
weeks). The more premature the infant/neonate, the
greater the likelihood that there will be insufficient
surfactant to sustain ventilation.
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Respiratory Obstruction in Children
• Increased airway resistance
– Extrathoracic airways (upper airways)
º Prolonged inspiration; inspirational stridor
º Inspiratory retractions as ribs are moved
outward and body wall does not expand
with rib cage
– Intrathoracic airways (lower airways)
º Prolonged expiration with wheezing
º Rib cage retractions as ribs are pulled
inward, but air does not leave lungs
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Obstructive Disorders
• Upper airway
– Croup
– Epiglottitis
• Lower airway
– Acute
bronchiolitis
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Question
Tell whether the following statement is true or false.
Epiglottitis causes stridor.
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Answer
True
Rationale: Epiglottitis affects the upper airway
(inflammation causes the lumen of the upper airway to
become more narrow). When the child inspires, it is
difficult to pass air through the narrowed airway. This
causes noisy inspiration/stridor.
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