Pleural Disease Flashcards
1
Q
Explain the pleura
A
- Pleura is connective tissue within the thoracic cavity. If it is in the abdominal cavity, it is the peritoneum.
- Pleura covering the surface of the lungs = visceral. If covering the throacic wall = parietal.
- It is one continuous lining layer: have your lung and it is like the lung being in a bag and in between the lung and the bag is your pleural space. The space between lung and ribs is filled with a small amount of fluid produced by lymphatic system (very small amount of fluid and very narrow space).
2
Q
Explain pleural cavity
A
- this is the narrow space between the visceral and parietal pleura.
- Contains a small amount of serous fluid.
- Allows for smooth movement of the lungs over the ribs etc.
- Under negative pressure.
3
Q
Explain pleural sacs and mediastinum
A
- Have left and right pleural sac around the lungs.
- Medistinum is the space between them. In most species, it is continous, it is more delicate in the horse. It is thin in the dog and cat, hence, likely to see disease on both sides.
4
Q
What’s pleural space disease?
A
Pleural space disease is accumulation of:
- Fluid = pleural effusion
- Air = pneumothorax
- Soft tissue mass
Clinical signs and severity will depend on the quantity of fluid/air/mass. As fluid/ air accumulates in the pleural space, you get loss of negative pressure, which causes the lungs to collapse.
5
Q
Clinical signs of pleural space disease?
A
- Restrictive breathing pattern
- Short, shallow breaths
- Tachypnoea
- Open mouth breathing
- Dyspnoea, resp distress
- Orthopnoea
- Cyanosis
Can be acute or chronic.
6
Q
Explain how pleural fluid is made
A
Fluid produced mainly from parietal pleural vessels by capillary filtration
Fluid readsorbed primarily via parietal lymphatic vessels
Tends to come from parietal vessels: blood pressure forcing fluid out and absorbed mainly in parietal pleural through lymphatic vessels. Very little done by the visceral pleura.
7
Q
How does effusion occur?
A
- Pleural effusion is controlled by starling’s forces. It occurs when pleural fluid dynamics favours decreased pleural fluid absorption or increased fluid formation.
- it can be unilateral or bilateral.
8
Q
What would you expect with pleural space disease?
A
- Accumulation of fluid = pleural effusion
- On ascultation: muffling of lung and heart sounds especially ventrally.
- Percussion: increased dullness (fluid line)
- Different fluid types can be present: transudate, modified transudate, exudate etc.
9
Q
What would you expect from a transudate effusion, modified transudate or exudate effusion?
A
Transudate
- Most common cause of a pure transudate is hypoalbuminaemia which can be caused by a protein losing enteropathy, nephropathy or liver disease.
Modified transudate
- Most common cause is due to increased hydrostatic pressure e.g. right sided heart failure, pericardial disease, pulmonic stenosis, cardiomyopathy, pulmonary hypertension.
- Can also be due to diaphragmatic hernia, lung lobe torsion or neoplasia.
Exudate
- Non septic effusion e.g. FIP, neoplasia, chylothorax, fungal infections.
- Septic effusion (pyothorax)
- Chyle (chylothorax) - disruption of the thoracic duct.
- Blood (haemothorax) - trauma, coagulopathy, neoplasia etc.
10
Q
Initial management of a patient with pleural disease?
A
- Oxygen supplementation
- Emergency thoracic ultrasound to make the diagnosis
- In severely dyspnoeic patients DO NOT RADIOGRAPH - these patients are very unstable and will die if they are stressed!
- Immediate thoracocentesis
- Immediate relief from clinical signs
- Diagnostic
- Cytology, cell counts, protein content, bacterial culture
- Stabilise the patient prior to further investigations
11
Q
Indications for throacostomy (chest drains?)
A
- Animals that will require multiple thoracocentesis over a short period of time
- If large volumes of effusion
- Pneumothorax
- Chest wall injuries
- Flail chest / Flail segment
- Bite wounds
- Most pyothorax cases
12
Q
Pneumonthorax pathogenesis?
A
- Traumatic
- Rib fractures causing laceration of the pleura
- Open wounds through the chest wall
- Compression of thorax with a closed glottis leading to trauma to the conducting airways / alveoli resulting in rupture
- Iatrogenic
- Bronchoscopy, thoracocentesis, FNAB (fine needle aspirate biopsy) of lungs, prolonged periods of ventilation (care to not overventilate the lungs).
- Spontaneous
- Leakage from pulmonary abscesses, neoplasia, foreign body migration, ruptured intrapulmonary bullae, ruptured subpleural blebs, pneumonia, feline asthma
- Infectious
- Gas forming bacteria in the pleural space
13
Q
Pathophysiology of a pneumothorax?
A
- Loss of coupling efficiency between the elastic rib cage and elastic lungs
- Leading to partial lung collapse, decreased tidal volume and increase in overall lung volume due to expansion of the rib cage
- Severity of clinical signs depend on the degree of pneumothorax and the extent and presence of other pathology.
- Have air in the chest and small amount of fluid – you lose that ability of the rib cage to expand and pull lungs up – lose that coupling, so lungs tend to collapse and decreased amount of lung expansion and essential, gas exchange not occurring as normal.
- Tension pneumothorax
- Slightly different – associated with a one way valve leak, as animal continues to breathe, more and more air is forced out of the lungs into the pleural space, so can lead to really severe lung compression – can be rapidly life threatening.
- Leads to severe lung compression and a severe and profound hypoxaemia develops. Equilibration of pleural pressure and CVP develops leading to reduced venous return leading to reduced CO. Hypoxaemia, hypercapnia and systemic hypotension develop and are rapidly life threatening.
*
14
Q
Diagnosis of a pneumothorax?
A
- Physical examination
- Assessment of respiratory status
- Observe before you get too close.
- Thoracic radiographs – if stable enough
- [Routine haematology / biochemistry]
- Depends: pyothorax or neoplasia may see changes in haematology.
- Blood gases
- Tells you how well gas exchange is working.
- Pulse oximetry
- Insensitive, but once it starts to drop, you know you have a problem.
15
Q
Differential diagnosis for pleural effusion in horses?
A
- Pleuropneumonia ***
- Main cause and much more common than anything else!
- Neoplasia
- cranial mediastinal lymphosarcoma
- malignant melanoma
- mesothelioma
- others
- Right-sided heart failure
- Pericarditis
- Majority of horses with PE have pleuropneumonia
