Respiratory: Pleura

Question 1

What is hyrdostatic pressure?

Answer 1

the force that blood exerts on the blood vessel walls

Question 2

Why does the hydrostatic pressure of the lung capillaries increase in heart failure?

Answer 2

When the heart isn’t pumping blood effectively there is backing up into the pulmonary vessels and this causes high pressure which then causes fluid to back up out of the capillaries and into the pleural space, causing a pleural effusion.

Question 3

Whart are some causes of reduced oncotic pressure? What does this mean?

Answer 3

Oncotic pressure is the movement by osmosis across capillaries. Fluid leaks out into the pleuralpace when this oncotic pressure is reduced.

1. Cirrhosis (less proteins made)
2. Nephrotic syndrome (lots of protein being lost)

Question 4

What causes a transudative pleural effusion?

Answer 4

Too much fluid leaving the lung capillaries (either due to increased hydrostatic pressure or decreased oncotic pressure.

Question 5

What causes an exudative pleural effusion?

Answer 5

Inflammation to the pulmonary capillaries which makes them much more leaky. This allows fluids, immune cells and LDh to leak out and into the pleural space. This can cause trauma, malignancy, infection or inflammation.

Question 6

What is a chylothorax?

Answer 6

The thoracic duct is damaged (usually during surgery) and lymphatic fluid accumulates in the pleural space. It can also be caused by tumours in the mediastinum.

Question 7

What does a pleural effusion look like on X Ray?

Answer 7

Blurring of the costophrenic angle as fluid displaces the air.

Question 8

In a thoracocentesis is the needle placed above or below a rib?

Answer 8

Above - so as not to damage the neurovascular bundle which sits below each rib.

Question 9

Which type of effusion looks clear and which looks cloudy?

Answer 9

Transudative: Clear
Exudative: Cloudy (due to immune cells)
Lymphatic (milky)

Question 10

What is the difference in composition of transudative and exudative pleural effusions?

Answer 10

Exudative fluid has much more protein in it and also has immune cells.
The light critera states that an exudative pleural effusion is diagnosed if the fluid protein is greater than 30g/L.

Question 11

How do you treat pleural effusions?

Answer 11

Remove fluid with a thoracocentesis and treat underlying cause.

Question 12

What is the immediate treatment of a large unilateral pleural effusion?

Answer 12

Diagnostic tap

Contrast CT to look for malignancy (particularly exudative effusions)