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Pneumonia 2


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Define Pneumonia
Infectious exudative inflammation of the distal
portions of the lung: terminal airways, alveolar spaces and interstitium.

- inflammatory dx
- vascular response production (hyperemia & vascular permeability)
- exudate
What are the qualifiers used to describe pneumonia?
Qualifiers used to imply:

1) Etiology (viral bronchopn)
2) Infection Mech (aspiration pn)
3) Anatomic site (upper lobe pneumonia)
4) Clinial course (acute bacterial pn)
What agents cause pneumonia?
Bacteria, viruses, fungi and parasites may all cause pneumonia.
4 routes of bacterial inoculation of the lung
1. aspiration of contaminated oropharyngeal secretions
2. inhalation of airborne bacteria or viruses
3. bacteremia
4. direct extension into the lungs

- first two are common causes of pneumonia.
What are the defense mechanisms used by the lungs against pneumonia?
1. respiratory filtering: airborne particles are filtered from inspired air
according to size.
2. Do not meet other criteria (resistance to: drying,
ultraviolet light and temperature change) necessary for transmission of
disease by the airborne route.
3. laryngeal competence
4. cough
5. mucociliary transport (ciliated cells, secretory cells, secretions)
6. Phagocytic and inflammatory cells
7. Immune responses (humoral (IgA, IgG & cellular)
What is the defense augmentation used against pneumonia?
Via vaccination:
1. pertussis (whooping cough)
2. Pneumovax (pneumococcal vaccine)
3. influenza vaccine
4. Hemophilus B vaccine
What are the agents causing pneumonia?
1. Streptococcus pneumoniae
2. Hemophilus influenzae
3. Staphylococcus aureus
4. Gram negative enteric bacilli
5. Mycoplasma pneumoniae
6. Chlamydia pneumoniae
7. Moraxella catarrhalis
8. Legionella pneumophila
9. Anaerobes
10. Viruses
11. Pneumocystis carinii
What is the characteristic pathologic changes seen in bacterial pn?
Exudate contains:
- edema fluid
- red blood cells
- leukocytes (principally neutrophils)
- fibrin
How is bacterial pneumonia classified?
<ay be classified on the basis of the causative organism (clinically most important!) or the pattern of anatomic involvement: lobar
pneumonia or bronchopneumonia.
What is lobar pneumonia?
Exudative inflammation involving a whole lobe(s) or
a large portion of a lobe of lung.
- 90-95% of cases are caused by Streptococcus pneumoniae.
- Four stages
What are the 4 stages of lobar pn?
a. Congestion (vascular engorgement, intra-alveolar fluid,small numbers of
b. Red hepatization (extravasation of red cells into alveolar spaces)
c. Gray hepatization
(Red cells disintegrate, with persistence of neutrophils and fibrin)
d. Resolution (lungs return to NL)
What is bronchopneumonia?
Focal areas of suppurative
inflammation, in a patchy distribution, involving one or multiple lobes.
What are the complications if bacterial pneumonia does not resolve?
Complications include:
a. abscess formation
b. spread of the infection to the pleural cavity (empyema)
c. bacteremia, with spread of the infection to distant sites
d. organization of the exudate
What is an abscess and what etiologic mechanisms are involved?
Abscess= localized suppurative process characterized by tissue necrosis.

- Etiologic mechanisms include:
a. aspiration of infected material
b. septic embolism
c. direct trauma
d. spread from adjacent structures
What are the characteristic changes seen in viral pneumonia?
a. mucosal hyperemia
b. mononuclear cell infiltrate
c. edema
d. +/- necrosis
How may viral pneumonia present pathologically?
a. acute interstitial pneumonia (e.g. CMV)
b. necrotizing bronchopneumonia (e.g. Adenovirus)
c. focal parenchymal necrosis
How would one differentiate b/t viral and bacterial infections of the lung?
Viral infections - edema & mononuclear cell infiltrate that predominantly involves the interstitium.
Bacterial pneumonias- neutrophilic exudate that fills the alveolar spaces and causes relatively little change in the interstitium.
Viruses also may induce characteristic cytopathic changes that allow identification of virus by examination of tissue section.
What is pulmonary TB?
Pulmonary infection with Mycobacterium tuberculosis is acquired as a result of
inhaling the tubercle bacillus suspended in coughed up aerosolized
sputum of an infected individual with "open" tuberculosis
- 2 phases exists
- primary TB
- Secondary TB
What are some features of an abscess?
- may occur in any location in the lung; they may be
single or multiple.
- abscess= cavity filled with suppurative debris. If communication exists with an airway, the exudate may
drain, leading to air in the cavity, and an air-fluid level on chest xray.
What is the clinical course of an abscess?
clinical course of an abscess is variable
What is primary pulmonary TB?
Infection in an individual not
previously exposed & sensitized to tubercle bacilli.
What is the sequence of events in primary TB?
Inhalation of infected airborne droplet->particle size (approximately 3 microns) favors deep
inhalation and retention of the organism->bacilli tend to locate in the subpleural midzone of lung->the earliest radiographic appearance is an ill-defined localized "atypical" pneumonia
->after a brief acute inflammatory reaction associated with a
neutrophilic response, the bacilli invoke granuloma
formation->by 2 to 8 weeks, the pneumonic focus becomes a more defined radiographic opaque single spheroidal lesion - the Ghon focus
What is the appearance of TB granulomas?
Granulomas (TB) are centrally necrotic. When visible macroscopically, necrotic granulomas resemble "yellowish-white cheese" -> caseous necrosis
What is a Ghon complex?
Combination of original peripheral Ghon focus + hilar node lesion
- tubercle enters lymphatics-> multiorgan hematogenous dissemination
What is the subsequent course of TB illness?
- bronchopneumonia or miliary TB
- Ghon complex calcification->
- latent stage may persist thru life
What is secondary (reactivation) TB?
TB which becomes clinically evident in an individual already sensitized to the
tubercle bacillus.
- most common source of secondary tuberculosis
- decline in host immunocompetence.
- location = lung apices
Lung Mechanics affected by pneumonia?
1. restriction: airspace and interstitial exudates decrease compliance (down
and rightward shift) in virtually every patient.
2. obstruction: much less common
3. Gas exhange obstruction - major pathophysiologic alteration
What are the 2 clinical presentation of pneumonia?
Typical and atypical pneumonia
What is the clinical presentation of typical pneumonia?
sudden onset, chills- common, cough-present, purulent sputum, pleuritic pain, focal crackles, rare wheezing, air space filling CXR infiltrate, S, pneumoniae
What is the clinical presentation of atypical pneumonia?
slower onset, rare chills, prominent cough, dry sputum, MSK pain, diffuse crackles, diffuse, interstitial infiltrate, M. pneumoniae
What is essential in determining a diagnosis of pneumonia?
New radiographic infiltrate
and one major criteria or 2 minor criteria
mj=fever, sputum, cough
mn=leukocytosis, dyspnea, pleuritic chest pain, consolidation
What are the different types of treatment approaches?
1. Syndrome Recognition
2. Diagnositc search (infected material examination, culture, serologic & antigenic investigations)
3. Guidelines for CAP & nosocomial pn
What are the complications of pneumonia?
1. Lung abscess=fluid filled cavity
2. Empyema=infected pleural effusion

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