SM 172 Pleural Diseases Flashcards
Describe the pleural place normally?
Normally, the pleural space is a thin layer of cells that is often described as a potential space
What lines the chest wall?
Parietal pleura
What lines the lungs?
Visceral pleura
If one pleural space is compromised, what happens to the other?
No effect on the other; there are two distinct pleural spaces on either side of the body that do not connect
What is the main function of the pleura?
Lubricate the organs and act as a reservoir for excess lung fluid, delaying the formation of pulmonary edema
Which pleural lining receives blood flow from the systemic circulation?
Both the parietal and visceral pleura receive blood flow from the systemic circulation
Which pleural layer is under higher pressure?
The parietal layer is under higher pressure because the visceral pleura drains into the lower pressure pulmonary veins, and is thicker, diminishing the pressure difference
What differentiates the Parietal and Visceral pleura?
Parietal is higher pressure, has lymphatic stoma, and is thinner; Visceral is low pressure, lacks lymphatic drainage, and is thicker
What sets the balance of fluid flow in the interstitial space?
The Frank-Starling equation: Q = K*((Pv - Pi)-u(Oi-Op)); Q always refers to flow out of the vessels
What happens in the pleural space at rest, with respect to filtration and drainage?
Normally, Q is slightly positive leading to fluid influx into the pleural space, which is drained by the lymphatic stoma
What do the parietal lymphatic stoma do?
They generate a strong rhythmic pumping action that creates a negative pressure which sucks fluid out of the interstitial space
What does the development of a pleural effusion suggest?
Pleural effusions develop when there is an imbalance between filtration and drainage in the pleural space
What is the radiographic correlate of a Pleural Effusion?
On CXR, a meniscus sign is seen during a Pleural Effusion
What is a Meniscus sign?
A fuzzy curved line that appears in a lung during a Pleural Effusion
How does congestive heart failure precipitate pleural effusion?
CHF increases microvascular hydrostatic pressure leading to pleural effusion
How does low albumin and nephrotic syndrome precipitate pleural effusion?
Decreased vascular oncotic pressure favors filtration and leads to pleural effusion
How does malignancy cause pleural effusion?
Malignancy can obstruct lymphatic drainage leading to pleural effusion
How does trapped lung lead to pleural effusion?
An abnormally thickened visceral pleura decreases pleural space pressure and favors filtration leading to pleural effusion
How does increased permeability of capillaries or pleural lining lead to pleural effusion?
Damage to the capillaries via ARDS leads to the filtration coefficient dropping to 0, therefore cancelling the effects of the oncotic pressure gradient and allowing the hydrostatic pressure gradient to drive filtration out of the capillaries and cause pleural effusion
How does pleural effusion present?
Pleural effusion is often asymptomatic, but may have nonspecific symptoms like cough and edema
Why is pleural effusion often asymptomatic?
Due to hypoxic vasoconstriction
How does pleural effusion show up on physical exam?
Dull to percussion and decreased breath sounds
What is a tension pleural effusion?
Occurs when an entire lung is compressed by a pleural effusion and pressure builds up on one side, displacing the heart and other mediastinal structures as well as impairing venous return to the heart and dropping CO
Is CXR able to diagnose a pleural effusion?
Sometimes; but it’s possible to miss it
What does a pleural effusion look like on Ultrasound?
Black fluid above the lung
What is the benefit of an Ultrasound in pleural effusion treatment?
The ultrasound shows you a black space where you can stick a needle to drain the pleural effusion
What are the complicated effusions an Ultrasound can detect and why is this helpful?
Ultrasound can show loculated effusion (looks like lots of little cavities in the lung) as well as layering hemothorax, both of which require a large chest tube to drain the pleural effusion
What is the diagnostic test for a pleural effusion?
Thoracentesis, which obtains a sample of the pleural fluid
What are Light’s Criteria used for?
Classify a pleural effusion as exudative if any one of three conditions is met, or transudative if none of the three conditions are met