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
List the Light’s Criteria?
Pleural Total Protein/Total Serum Protein > 0.5
Pleural LDH/Serum LDH > 0.6
Pleural LDH > (2/3) of Upper Normal Serum LDH
Are transudative effusions positive or negative on Light’s Criteria?
Transudative effusions are negative on all 3 of Light’s criteria
What are common causes of transudative Pleural Effusion?
CHF, Cirrhosis, Nephrotic Syndrome
What are common causes of Exudative pleural effusion?
Parapneumonic, malignancy, autoimmune disease, pulmonary embolism, pancreatitis
What is the order of tests in classifying pleural effusion?
Ultrasound -> Thoracentesis -> If exudative, Cell Count/pH/Glucose/Cultures/Cytology
After determining a pleural effusion is exudative, what is the point of a cell count?
High neutrophils = infection
High lymphocytes = malignancy, TB, autoimmune diseas
What do high neutrophils in a pleural effusion tell you?
High neutrophils mean an infection is driving the pleural effusion
What do high lymphocytes tell you in a pleural effusion?
High lymphocyte suggest a malignancy, TB, or autoimmune disease is driving the pleural effusion
After determining a pleural effusion is exudative, what is the point of a pH?
pH < 7.2 (more acidic) indicates an active infection and requires directly inserting a large chest tube
After determining a pleural effusion is exudative, what is the point of a Glucose measurement?
Low glucose = active infection
After determining a pleural effusion is exudative, what is the point of growing cultures from the pleural effusion fluid?
If cultures are grown, common bacteria that cause community acquired bacteria can be detected
After determining a pleural effusion is exudative, what is the point of cytology?
Search for malignant cells
What is Empyema?
Empyema is pus in the pleural space, and indicates active infection with the need for drainage using a large chest tube immediately
What is a Chylothorax?
Chylothorax is a triglyceride rich pleural effusion that occurs due to impaired lymphatic drainage, and can be cleared with a large chest tube
How should a transdutative pleural effusion be treated?
Treat the cause of the pleural effusion, ie congestive heart failure, and the effusion will resolve on it’s own
When is thoracentesis always indicated?
New, unilateral pleural effusion = thoracentesis
What is Pneumothorax?
Air in the pleural space
What are the 3 types of Pneumothorax?
Primary spontaneous, secondary spontaneous, and traumatic/iatrogenic
What are the characteristics of a Primary Spontaneous Pneumothorax?
No underlying lung pathology, no inciting event, young thin patients, high recurrence rate
What is a “lung line”?
In a pneumothorax, air flows into the pleural space and compresses the lung, creating an area on the periphery of the lung where lung markings are absent
What are the characteristics of a Secondary Spontaneous Pneumothorax?
Spontaneous pneumothorax in the setting of underlying lung disease
How does Cystic Fibrosis present on CXR?
Upper lobe predominant cysts and traction bronchiectasis
What diseases can predispose secondary spontaneous pneumothorax?
Cystic Lung Diseases (CF), Infection (pneumonia), and Malignancy (cancer)
How can cystic lung diseases predispose secondary spontaneous pneumothorax?
Cystic lung diseases create cysts in the lung that can pop and release air into the interpleural space
How can infection predispose secondary spontaneous pneumothorax?
Infections can form cavitary lesions on the lung, such as S. Aureus, which can burst and release air into the interpleural space
How can malignancy predispose secondary spontaneous pneumothorax?
Malignancy can erode the pleural lining and predispose pneumothorax
How can trauma cause pneumothorax?
Trauma can puncture the parietal pleura and allow air to enter the pleural space, creating a pneumothorax
What procedures can generate Iatrogenic pneumothorax and why?
IR Biopsies, Bronchoscopy, tracheal tube, central line placement; in these procedures, the pleural space may be punctured
How might a tracheal tube form a pneumothorax?
If the tube is pushed too far into the lung, it can burst through the lung and pierce the parietal pleura, forming a pneumothorax
How can a central line placement cause a pneumothorax?
The sharp tip of the line is normally inserted into the subclavian vein, but can break out of the vein and pierce the parietal pleura, resulting in a pneumothorax
What is a trapped lung?
Inflamed visceral pleura that becomes scarred and permanently compresses the lung, allowing pleural effusions to form forever
Can a trapped lung be treated with a chest tube?
No; even if the pleural effusion is drained, the lung is unable to expand and eventually the pleural effusion will reform
What is the gold standard for diagnosis of a pneumothorax?
Chest CT, but ultrasound is being used more
What is a lung point?
The lung point is where the intense line on ultrasound that represents both the visceral and parietal layers stops shimmering, as at this point gas is in between the two layers
Which is worse, an open or closed pneumothorax?
Closed pneumothorax, because air cannot escape the chest cavity, resulting in worse hemodynamic effects
Describe an open pneumothorax?
A hole in the parietal lining allows air to enter the pleural space and compress the lung, since the interpleural pressure becomes equal to atmospheric pressure; however, breathing can still occur because the interpleural pressure can be lowered and raised
Why is expiration possible in an open pneumothorax but not a closed pneumothorax?
In an open pneumothorax, air can still escape through the hole in the parietal pleura, allowing expiration to occur
In a closed pneumothorax, the hole is a one way valve that only allows air in, but not out, blocking expiration
Describe a closed pneumothorax?
A hole in the parietal pleura allows air in but not out of the pleural space, raising interpleural pressure greatly and shifting the mediastinal contents to restrict venous filling/cardiac output as well as inhibiting expiration
How can a closed pneumothorax be seen on CXR?
The entire mediastinum is shifted in the opposite direction of the lobe with the pneumothorax
What is a subcutaneous emphysema?
Air in the subcutaneous tissue that can be felt as popping, following a pneumothorax
What is the emergency treatment for a pneumothorax?
Needle decompression
How does needle decompression work?
In an emergency, it allows air to escape the pleural cavity, resulting in lowered interpleural pressure and increased venous return, raising cardiac output
Is a pleural space required for life?
No
What is a tension pneumothorax?
A pneumothorax that reaches high pressures which impair filling of the heart, causing circulatory collapse and require immediate drainage of the pleural space
Why are ventilators a risk for tension pneumothorax?
Normal ventilation maintains a negative interpleural pressure; ventilated patients get Positive End Expiratory Pressure which raises PIP due to increased stretch of the lung, which can impair venous return to the heart
