244 Diseases of the Pleural Space

Question 1

How does pleural effusion affect lung function?

Answer 1

• Pleural effusion affects lung function by creating restrictive defect with decreased total lung capacity (TLC) and functional residual capacity (fRC)
• Advanced cases there is increased ventilation-perfusion mismatch and if left, severe pleural effusion result in decreased cardiac output and ultimately cardiac arrest
• as pleural effusion forms, there is collapse of lung parenchyma, and increase in intrathoracic pressure.

Question 2

What is ‘lung entrapment’?

Answer 2

• Lung entrapment is a disorders that develops in association with active pleural inflammation or neoplasia.
• Immature fibrin and overlying inflammation prevent re-expansion, and contribute to failure to recruit lung after thoracocentesis.

Question 3

What is ‘trapped lung’?

Answer 3

• During long standing effusions, there is thickening and constriction of visceral pleura and thickening of parietal pleura.

= lung that is tightly constricted by overlying visceral pleura, and cant re-expand, in presence of negative intra-thoracic pressure.

• The non-recruitable lung could be associated with development of thoracocentesis- associated pneumothorax.

Question 4

What are the clinical signs of pleural space disease?

Answer 4

• tachypnea, orthopnea, or overt difficulty breathing with classically rapid/shallow breathing considered the most common manifestation
• some animals have marked abdominal effort
• Diffuse or dependent muffled heart/lung sounds; occasionally lung sounds can appear normal.

Question 5

What is the initial diagnostic evaluation?

Answer 5

• Diagnosis of pleural effusion or pneumothorax can be made either through thoracocentesis or diagnostic imaging.
• CT and MRI can demonstrate pleural effusions and pneumothorax, but used less commonly as the initial DI modality
• Rads: decreased detail scalloping of ventral lung borders, fissure lines between lung lobes and obscured cardiac silhouette. A DV helps confirm presence of pleural effusion with minimal stress on the patient. Rounded lung margins can represent pleural fibrosis.

Question 6

How is pleural effusion managed?

Answer 6

• Thoracocentesis is performed by clipping and aseptically preparing the area between the seventh and ninth rib near the costochondral junction.

Question 7

What are some complications of thoracocentesis?

Answer 7

• iatrogenic pneumothorax can occur from damage to thickened/fibrotic visceral pleural and lung parenchyma or marked drops in intrathoracic pressure which result in formation of spontaneous tears in lung/pleura and subsequent creation of pulmonary-pleural fistula.

Small volume iatrogenic pneumothorax can occur from damage to thickened/fibrotic visceral pleural and lung parenchyma or from marked drops in intrathoracic pressure which result in formation of spontaneous tears in lung/pleura and subsequent creation of pulmonary-pleural fistula.

Question 8

What are thoracostomy tubes used for?

Answer 8

• Thoracostomy tubes can be for management of pleural effusion or pneumothorax in cases with large volume effusion or air that is recurring quickly, infectious effusion, or post-operatively.

Question 9

What is the different fluid appearance?

Answer 9

• purulent, chylous (milky), hemorrhagic, serous or serosanguineous, or icteric.
• Most effusions are serous or serosanguineous
• neoplastic: carcinoma, lymphoma, small lymphocytes, neutrophils, bacteria, RBCs, macrophages, and mesothelial cells.

Question 10

What are the characteristics of transudate pleural effusion?

Answer 10

transudate:
TP = <2.5g/dL
Cell=<2500 cells/mcl
Cell type: nondegenerative neutrophils, macrophages, mesothelial cells

E.g. low albumin - PLE