1.1.3: Lung disease - alveolar disease Flashcards
Where do you localise respiratory problems to?
- URT obstruction
- Loss thoracic capacity (pleural space disease)
- Pulmonary parenchymal disease (alveolar/interstitial)
- Non-CRS conditions (metabolic/physiologic)
Clinical signs of pulmonary parenchymal disease
- Increased inspiratory and expiratory effort
- Some interstitial diseases limit compliance -> increased inspiratory effort predominates
- Cough may/may not be present -> only happens when disease has moved into terminal bronchi
- Less common signs: haemoptysis, collapse/syncope, cyanosis
- Occasionally minimal signs of respiratory disease noted even with severe pathology (esp cats)
Where are cough receptors present: alveoli or airways?
Airways.
There are no cough receptors in the alveoli.
What do crackles tell you?
- There is something wrong in the lung and you need to image them
- Crackles are produced by air being dragged through fluid
- These are not definitive for alveolar disease
Clinical signs of aspiration pneumonia
- Cough
- Harsh/reduced lung sounds
- Tachypnoea
- Pyrexia
- Check oxygenation -> serial evaluation
How do you diagnose aspiration pneumonia?
- Radiographs show alveolar infiltrate (patchy or focal)
- Most commonly affected lung lobes: right middle, right cranial, left cranial; in aspiration penumonia, material tends to enter cranial lung lobes
- Need BAL to confirm diagnosis: cytology, check for neutrophils/toxic neutrophils
You suspect aspiration pneumonia and confirm the diagnosis with BAL and cytology. What antibiotics will you treat with?
- Ideally based on C&S
- Broad spectrum antibiotics as often not sure what we’re dealing with e.g. amoxicillin or amoxy/clav, OR TMPS
Examples of alveolar disease
- Aspiration pneumonia
- Pulmonary oedema (may be cardiogenic/ non-cardiogenic)
- Pulmonary haemorrhage
- Eosinophilic lung disease
- (Pulmonary parasites)
- (Pulmonary neoplasia - primary or metastatic)
- (Infectious pneumonia)
Histological appearance of bronchopneumonia (e.g. aspiration pneumonia)
- The airway and alveoli are full of neutrophils
- There are no air-filled spaces evident at all in a fully consolidated area)
- Other areas may be less severely affected
Treatment of aspiration pneumonia
- Supportive care: oxygen therapy, antibiotics (take care not causing oxidative damage to already fragile lung)
- Treat any underlying cause
- Consider anti-acid medication if frequent occurence (caution with this; it may increase gastric bacterial load)
- Metoclopramide improves motility and lower oesophageal sphincter tone
What is pulmonary oedema?
Pulmonary oedema: when there is fluid accumulation in the interstitium and subsequently in the alveoli at a rate that exceeds removal.
* This in turn leads to V:Q mismatching and hypoxaemia (areas of lungs are still being perfused, but can’t be ventilated)
What (physiologic) conditions can pulmonary oedema be a consequence of?
- Increased hydrostatic pressure
- Reduced oncotic pressure
- Increased vascular permeability
- Impaired lymphatic drainage
Describe how pulmonary oedema develops
- Initially there is fluid accumulation in the interstitium
- This quickly floods the alveoli
- There is then ventilation: perfusion mismatch
What are the two types of pulmonary oedema and what types of fluid are formed in each?
- Cardiogenic - due to increased hydrostatic pressure; fluid is building up behind the failing heart - fluid formed is low-protein
- Non-cardiogenic - the result of lung damage that increases vascular permeability and so protein leaks out - fluid formed is high protein
Possible causes of non-cardiogenic pulmonary oedema
Most commonly: pulmonary epithelial injury
* Choking
* Near-drowning
* Electric shock
* Head trauma
* Smoke inhalation
* SIRS
True/false: hypoalbuminaemia is a common cause of pulmonary oedema
False
Pulmonary lymphatics are very efficient so hypoalbuminaemia rarely causes pulmonary oedema.
Pulmonary oedema
What is the relevance of the lag phase to radiographs of an animal after an RTA?
- Lag phase - it takes time for the blood to fill the alveoli
- The thoracic radiographs taken immediately after the injury may appear normal
Describe the damage caused by a physical lung injury and how you would approach treatment
- Blunt trauma -> can cause pulmonary contusion (this causes ventilation/perfusion mismatch)
- Give supportive care with oxygen ASAP
- The haemorrhage needs to resolve itself - we can’t fix it
- Other treatment as required e.g. stabilisation of thoracic wall, analgesia
True/false: eosinophilic lung disease will cause alveolar signs.
False
Eosinophilic lung disease can cause alveolar or interstitial disease.
Signalment and clinical presentation for different eosinophilic lung diseases
- Eosinophilic bronchopneumopathy (EBN) is more common in dogs
- Reactive eosinophilic airway disease occurs in cats
- Typically young adults
- There is acute or chronic presentation, usually coughing
- May see weight loss
Diagnosis of eosinophilic lung disease
- Radiographs can show diffuse bronchointerstitial pattern although can see alveolar patterns (when there are dense infiltrates)
- Circulating eosinophils are seen in 50% of affected dogs; some will have hypereosinophilic syndrome
- BAL is best for diagnosis -> look for parasites, neoplasia, and fungal disease.
- BAL cytology shows eosinophils and some neutrophils too.
Treatment of eosinophilic lung disease
- Prednisolone 1-2mg/kg daily
- Outcome good unless other organs involved in which case prognosis is guarded
What antibiotic would you select to treat Mycoplasma infection?
Doxycycline
What is the difference between pleural effusion vs. interstitial pattern?
- In pleural effusion - the lungs are collapsed
- In interstitial lung patterns, the lungs are open, but diseased
