Pneumonia Flashcards
What is pneumonia?
Infection of lung tissue
When does pneumonia occur?
Whenever the host immune system is compromised (chronic diseases, immunosuppression, age) or the local defenses of the lungs are compromised.
How can pneumonia be classified?
Anatomical classification - lobar pneumonia or bronchopneumonia
Etiological classification
Classification by clinical setting - community acquired, hospital acquired, aspiration pneumonia, pneumonia in immunocompromised host
What is lobar vs bronchopneumonia?
Lobar pneumonia - entire lung lobe is affected
Bronchopneumonia - infection starts in bronchi and bronchioles then spreads to adjacent lung tissue in patchy manner
What is the causative agent for community acquired-bacterial pneumonia?
Bacterial or viral
Bacterial infection often follows an URTI
Strep pneumoniae is the most common causative organism
Bacterial pneumonia can present as lobar pneumonia or bronchopneumonia
Name the four defined stages mirroring the acute inflammation that takes place in lobar pneumonia.
1 - Congestion (vasodilation of alveolar capillaries & fibrin-rich exudation into alveoli)
2 - Congestion still present, neutrophils start to migrate into alveolar spaces. Alveoli are now solid, lung tissue is now the consistency of liver tissue. Red = congestion. Hepatization.
3 - neutrophils replaced by macrophages. Congestion subsides - Grey Hepatization.
4 - Stage of Resolution. Enzymatic digestion of the exudate occurs. Phagocytosis by macrophages.
What are the patterns of bronchopneumonia?
Foci of inflammation are patchy and are centered around the bronchi. Shows infection starts in bronchi and spreads to adjacent lung tissue.
What are examples of viruses causing community acquired viral pneumonia?
Influenza virus types A and B
Respiratory syncytial virus (RSV)
Adenovirus
What type of pneumonia do community acquired viral pneumonia cause?
Atypical pneumonia - inflammatory exudate is mainly in the alveolar walls instead of the alveolar spaces
Called interstitial, mainly mononuclear cells
What bacteria can cause atypical pneumonia?
Mycoplasma pneumoniae
What is a complication of viral pneumonia?
Acute Respiratory Distress Syndrome (acute lung injury)
What happens in ARDS?
Initiated by injury of pneumocytes and pulmonary endothelial cell activation
Endothelial activation leads to increase in capillary permeability and fibrin rich fluid exudate fills the alveoli.
Protein rich edema fluid + necrotic epithelial cells form a hyaline membrane against alveolar walls = compromising gas exchange
What is the common organism causing pneumonia in the immunocompromised host?
Fungus pneumocystis jirovecii (AIDs defining opportunistic infection)
What is pneumocystis pneumonia (PCP)?
AIDs defining opportunistic infection
Risk of infection is inversely proportional to the CD4 T cell count in HIV infected patients
What causes Pneumocystis Pneumonia?
Reactivation of a prior latent infection
What type of pneumonia does pneumocystis pneumonia cause?
Interstitial type of pneumonia similar to atypical pneumonia
Inflammatory infiltrate is seen in the alveolar walls
Causes inflammation and fungus kills type II pneumocytes (which release surfactant) = foamy cotton candy exudate within alveolar spaces
What causes aspiration pneumonia?
Due to aspiration of gastric contents.
E.g. repeated vomiting, coma, anaesthesia or heavy sedation, neuromuscular disorders
Caused partly by gastric irritation and partly by oral bacterial flora
Usually severe or fatal/could lead to lung abscesses if patient survives
