pneumonia

1. Pneumonia
By Dr.M.A.Ansari

2. Introduction
• Pneumonia is defined as acute inflammation of the lung parenchyma
distal to the terminal bronchioles (consisting of the respiratory
bronchiole, alveolar ducts, alveolar sacs and alveoli).
• The terms ‘pneumonia’ and ‘pneumonitis’ are often used
synonymously for inflammation of the lungs, while ‘consolidation’
(meaning solidification) is the term used for gross and radiologic
appearance of the lungs in pneumonia.

3. Pathogenesis
PATHOGENESIS The microorganisms gain entry into the
lungs by one of the following four routes:
1. Inhalation of the microbes present in the air.
2. Aspiration of organisms from the nasopharynx or
oropharynx.
3. Haematogenous spread from a distant focus of infection.
4. Direct spread from an adjoining site of infection.
Aspiration- a condition in which food , liquids , saliva or vomit
is breathed into the airways.

4. • The normal lung is free of bacteria because of the presence of a number of lung defence
mechanisms at different levels such as nasopharyngeal filtering action, mucociliary action
of the lower respiratory airways, the presence of phagocytosing alveolar macrophages and
immunoglobulins.
• Failure of these defence mechanisms may result in pneumonias.
These conditions are as under:-
1. Altered consciousness - The oropharyngeal contents may be aspirated in states causing
unconsciousness e.g. in coma, cranial trauma, seizures, cerebrovascular accidents, drug
overdose, alcoholism etc.
2. Depressed cough and glottic (opening between vocal cords) reflexes Depression of
effective cough may allow aspiration of gastric contents e.g. in old age, pain from
trauma or thoracoabdominal surgery, neuromuscular disease, weakness due to
malnutrition, severe obstructive pulmonary diseases, endotracheal intubation and
tracheostomy.
3. Impaired mucociliary transport The normal protection offered by mucus-covered
ciliated epithelium in the airways from the larynx to the terminal bronchioles is
impaired or destroyed in many conditions favouring passage of bacteria into the lung
parenchyma. These conditions are cigarette smoking, viral respiratory infections,
immotile cilia syndrome, inhalation of hot or corrosive gases and old age.

5. 4. Impaired alveolar macrophage function Pneumonias may
occur when alveolar macrophage function is impaired e.g. by
cigarette smoke, hypoxia, starvation, anaemia, pulmonary
oedema and viral respiratory infections.
5. Endobronchial obstruction Th e effective clearance
mechanism is interfered in endobronchial obstruction from
tumour, foreign body, cystic fibrosis and chronic bronchitis.
6. Immunocompromised states Disorders of lymphocytes
including congenital and acquired immunodeficiencies e.g.
AIDS, debility(physical weakness), senility(old age),
immunosuppressive therapy

6. Classification of pneumonia
There are several classification schemes for
pneumonias:
On the basis of the anatomic region of the lung
parenchyma involved, pneumonias are traditionally
classified into 3 main types:
1. Lobar pneumonia
2. Bronchopneumonia (or Lobular pneumonia)
3. Interstitial pneumonia.

7. Based on the clinical settings in which infection occurred, pneumonias
are classified as under:
1. Community-acquire pneumonia
2. Health care-associated pneumonia (including hospitalacquired
pneumonia)
3. Ventilator-associated pneumonia
Based on etiology and pathogenesis, pneumonias are classifi ed as
under
A. Bacterial pneumonia
B. Viral pneumonia
C. Pneumonias from other etiologies.

8. Bacterial pneumonia
• BACTERIAL PNEUMONIA is the Bacterial infection of the lung
parenchyma is the most common cause of pneumonia or
consolidation of one or both the lungs. Two types of acute bacterial
pneumonias are distinguished— lobar pneumonia and broncho-
(lobular-) pneumonia

9. Lobar pneumonia
• Lobar Pneumonia Lobar pneumonia is an acute bacterial infection of a
part of a lobe, the entire lobe, or even two lobes of one or both the
lungs.
ETIOLOGY
Based on the etiologic microbial agent causing lobar pneumonia,
following types of lobar pneumonia are described:
1. Pneumococcal pneumonia More than 90% of all lobar pneumonias
are caused by Streptococcus pneumoniae, a lancet-shaped diplococcus.
S. pneumoniae causes particularly virulent form of lobar pneumonia.
Pneumococcal pneumonia in majority of cases is community-acquired
infection.

10. • 2. Staphylococcal pneumonia Staphylococcus aureus causes
pneumonia by haematogenous spread of infection from
another focus or after viral infections.
• 3. Streptococcal pneumonia -haemolytic streptococci may
rarely cause pneumonia such as in children after measles or
infl uenza, in severely debilitated elderly patients and in
diabetics.
• 4. Pneumonia by gram-negative aerobic bacteria Less
common causes of lobar pneumonia are gram-negative
bacteria like Haemophilus influenzae, Klebsiella pneumoniae
(Friedlander’s bacillus), Pseudomonas, Proteus and
Escherichia coli, H. influenzae commonly causes pneumonia
in children below 3 years of age.

11. Pathogenesis of lobar pneumonia
• The sequence of pathologic changes is the inflammatory response of lungs
in bacterial infection.
• STAGE OF CONGESTION: INITIAL PHASE The initial phase
represents the early acute inflammatory response to bacterial infection that
lasts for 1 to 2 days. Grossly, the affected lobe is enlarged, heavy, dark red
and congested.
• Cut surface exudes blood-stained frothy fluid.
• Histologically, typical features of acute inflammatory response to the
organisms are seen. These are as
i) Dilatation and congestion of the capillaries in the alveolar walls.
ii) Pale eosinophilic oedema fluid in the air spaces.
iii) A few red cells and neutrophils in the intra-alveolar fluid.
iv) Numerous bacteria demonstrated in the alveolar fluid by Gram’s staining.

13. 2. RED HEPATISATION: EARLY CONSOLI DATION
This phase lasts for 2 to 4 days.
The term hepatisation in pneumonia refers to liver-like consistency
of the affected lobe on cut section. Grossly, the affected lobe is red,
firm and consolidated. The cut surface of the involved lobe is
airless, red-pink, dry, granular and has liver-like consistency. The
stage of red hepatisation is accompanied by serofibrinous pleurisy.
Histologically, the following features are observed
i) The oedema fluid of the preceding stage is replaced by strands
of fibrin.
ii) There is marked cellular exudate of neutrophils and of red
cells.
iii) Many neutrophils show ingested bacteria.

15. 3. GREY HEPATISATION: LATE CONSOLIDATION This phase
lasts for 4 to 8 days. Grossly, the affected lobe is fi rm and heavy. The
cut surface is dry, granular and grey in appearance with liver-like
consistency
• The change in colour from red to grey begins at the hilum and spreads
towards the periphery. Fibrinous pleurisy is prominent. Histologically,
the following changes are present
i) The fibrin strands are dense and more numerous.
ii) The cellular exudate of neutrophils is reduced due to disintegration
of many inflammatory cells as evidenced by their pyknotic nuclei.
The red cells are also fewer. The macrophages begin to appear in the
exudate.
iii) The cellular exudate is often separated from the septal walls by a
thin clear space.
iv) The organisms are less numerous and appear as degenerated forms.

17. 4.RESOLUTION
This stage begins by 8th to 9th day and is completed in 1 to 3 weeks.
However, antibiotic therapy induces resolution on about 3rd day.
Resolution proceeds in a progressive manner. Grossly, the previously
solid fibrinous constituent is liquefied by enzymatic action, eventually
restoring the normal aeration in the affected lobe.
The process of softening begins centrally and spreads to the periphery.
Th e cut surface is grey-red or dirty brown and frothy, yellow, creamy
fluid can be expressed on pressing. The pleural reaction may also show
resolution but may undergo organisation leading to fibrous obliteration
of pleural cavity. Histologically, the following features are noted:
i) Macrophages are the predominant cells in the alveolar spaces, while
neutrophils diminish in number. Many of the macrophages contain
engulfed neutrophils and debris.
ii) Granular and fragmented strands of fibrin in the alveolar spaces are
seen due to progressive enzymatic digestion.
iii) Alveolar capillaries are engorged(congested with blood)

19. LUNG IN LOBAR PNEUMONIA IN GREY
HEAPTISATION STAGE

20. CLINICAL FEATURES
• Classically, the onset of lobar pneumonia is sudden. The major
symptoms are: shaking chills, fever, malaise with pleuritic chest pain,
dyspnoea(difficulty in breathing) and cough with expectoration which
may be mucoid, purulent or even bloody. The common physical
findings are fever, tachycardia, and tachypnoea(abnormally rapid
breathing) and sometimes cyanosis if the patient is severely
hypoxemic(lack of oxygen)
• There is generally a marked neutrophilic leucocytosis. Blood cultures
are positive in about 30% of cases.
• Chest radio graph may reveal consolidation.
• Culture of the organisms in the sputum and antibiotic sensitivity are
most significant investigations for institution of specific antibiotics.
• The response to antibiotics is usually rapid with clinical improvement
in 48 to 72 hours after the initiation of antibiotics.

21. Bronchopneumonia
• Bronchopneumonia or lobular pneumonia is infection
of the terminal bronchioles that extends into the
surrounding alveoli resulting in patchy consolidation
of the lung.
• The condition is particularly frequent at the extremes
of life (i.e. in infancy and old age), as a terminal event
in chronic debilitating diseases and as a secondary
infection following viral respiratory infections such as
influenza, measles etc.

22. ETIOLOGY
The common organisms responsible for bronchopneumonia are
staphylococci, streptococci, pneumococci, Klebsiella pneumoniae,
Haemophilus influenzae, and gram negative bacilli like Pseudomonas
and coliform bacteria.
CLINICAL FEATURES
• The patients of broncho pneumonia are generally infants or elderly
individuals. Th ere may be history of preceding bed-ridden illness,
chronic debility, aspiration of gastric contents or upper respiratory
infection.
• For initial 2 to 3 days, there are features of acute bronchitis but
subsequently signs and symptoms similar to those of lobar pneumonia
appear.
• Blood examination usually shows a neutrophilic leucocytosis. Chest
radiograph shows mottled, focal opacities in both the lungs, chiefly in
the lower zones.

23. ALL THE VERY BEST TO MY DEAR
STUDENTS