resp notes 1 - skipped the start...

Question 1

mechanisms of lung edema

Answer 1

1. Increased permeability of the blood-air barrier.
   * increased vascular permeability
   * type I pneumocytes are barrier to fluid movement from blood to alveolus > damaged can cause pulmonary edema.
   *diseases that damage endothelial cells or type I pneumocytes
2. Increased venous pressure: left heart failure, or excessive administration of intravenous fluids.
3. Lymphatic obstruction: masses/tumours, etc. This is an uncommon mechanism of pulmonary edema.
4. • Reduced oncotic pressure caused by hypoproteinemia

Question 2

edema in the lung issue

Answer 2

• fills alveoli, etc. > prevents ventilation, diffusion
• disrupts surfactant, reducing lung compliance > more effort needed to expand

Question 3

lung hemorrhage vs congestion

Answer 3

• Hemorrhage usually causes focal, multifocal, or patchy areas of red-purple discoloration and increased firmness of lung.
• In contrast, congestion of the lung from heart failure or as a postmortem change is diffuse or nearly diffuse

Question 4

histologic indicator of previous hemorrhage in lung

Answer 4

Hemosiderin-laden macrophages persist in the alveoli

Question 5

thrombi in the lungs
- visible? when do they form?
- vs emboli in the lungs?

Answer 5

• usually not visible grossly
• form in situ in the lung in hypercoagulable states
• emboli may be grossly visible

Question 6

Pulmonary embolism
- causes

Answer 6

• endocarditis of the right heart valves
• liver abscesses in cattle
• jugular thrombi as a complication of intravenous injection
• occasionally other unusual primary site

Question 7

functional importance of pulmonary thrombosis or embolism

Answer 7

• depends on the extent of vascular obstruction.
• Minor thrombosis or embolism may result in pulmonary hemorrhages that are of no functional consequence
• Ischemia and infarction of the lung > if at periphery of the lung, orcirculation is also impaired
• right heart failure or sudden death because of obstruction to flow from pulmonary arterial branches

Question 8

ATELECTASIS
- Definition
- appearance

Answer 8

• failure of the lung (alveoli) to expand / inflate.
• reddened because capillaries are more closely spaced, and rubbery because of the absence of air
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  Causes:
• airway obstruction > air cannot enter alveoli, and trapped air is gradually absorbed
• compression of lung > pleural effusions, pneumothorax, rumen tympany/bloat, diaphragmatic hernia.
• Surfactant dysfunction > Surfactant reduces surface tension in the lung and permits expansion of the alveoli
• Congenital atelectasis: lung inflates after birth, so atelectasis in aborted or stillborn animals is normal.

Question 9

Over-inflation or air trapping in the lungs
- common?
- cause?

Answer 9

• excessive air distending alveoli. This is reversible if the cause can be corrected
• common in animals
• Cause: partial obstruction > gas enters l.ungs but cannot exit
  > Bronchiolitis (e.g. viral infection, recurrent airway obstruction, or bacterial pneumonia) or masses

Question 10

Interlobular and bullous emphysema
- definition
- cause
- appearance

Answer 10

• air bubbles within the interlobular septa or subpleural connective tissue.
• destruction of alveolar septa with subsequent loss of gas into the interlobular tissue
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  Causes:
• result of severe dyspnea due to interstitial lung disease
• barometric trauma (eg. pop-off valve closed)
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  lines of air bubbles are seen, corresponding to the interlobular septa

Question 11

Alveolar emphysema
- what is it? common?

Answer 11

• enlargement of alveolar airspaces due to destruction of alveolar walls.
• rare in animals

Question 12

Pulmonary carcinoma is unique in cats because:

Answer 12

• metastases, not the lung tumour, are frequently responsible for the presenting signs.
  -metastasizes to unusual places—footpad, skeletal muscle, bone, eye, or brain—and frequently invades through the pleura to cause pleural effusion

Question 13

The clinical manifestations of lung tumours result from:

Answer 13

• Lung failure from occupying space within the lung tissue
• Compressing an important structure such as the bronchus
• Invasion into the pleura, causing pleural effusion that leads to dyspnea
• Rupture leading to blood loss (hemangiosarcoma is a typical example)
• Metastasis (e.g. feline pulmonary carcinoma to the digit, described above)
• Systemic effects of malignancy: malaise, anorexia, weight loss
• Paraneoplastic syndrome: hypertrophic osteopathy, manifesting as periosteal new bone formation in the long bones

Question 14

BRONCHOPNEUMONIA
- cause / pathogenesis

Answer 14

• opportunistic bacterial pathogens, that reach the lung via the airways > colonize air spaces of bronchioles and alveoli
  > inflammatory response chases after the bacteria and therefore targets these air spaces, resulting in exudation of fluid (edema), plasma proteins (fibrinogen/fibrin), and infiltration of neutrophils and macrophages
• exposure to large numbers of bacteria (aspiration pneumonia) or impairment of the normal respiratory defences (by viral infection, stress, etc.)
  > often no damage to the bronchiolar and alveolar epithelium

Question 15

BRONCHOPNEUMONIA
common agents in various species

Answer 15

• Cattle, sheep, and goats: Mannheimia haemolytica, Histophilus somni, Pasteurella multocida, Mycoplasma bovis.
• Swine: Actinobacillus pleuropneumoniae, Pasteurella multocida.
• Horses: Streptococcus zooepidemicus, Rhodococcus equi.
• Dogs: Streptococcus sp., Bordetella bronchiseptica. Aspiration pneumonia is particularly important in dogs, and typically results in mixed growth of E. coli and other bacteria within the lung.
• Cats: Bordetella bronchiseptica, Pasteurella multocida, Streptococcus sp., Mycoplasma felis.