Pleural Diseases Flashcards
Are most pleural effusions symptomatic?
Nope, slow developing ones tend to be asymptomatic (unless they are tension or large)
What is the embryonic origin of the lung?
mesothelial
“Layers of collagen and elastin covered by a single layer of mesothelium.”
this describes what?
the parietal and visceral pleura
Which layer of the pleura plays the main role in producing pleural fluid?
the parietal pleura
Where do the pleura receive blood from?
Systemic circulation
Where in the pleural layers is microvascular fluid filtration pressure lower? why?
microvascular fluid filtration pressure is lower in the visceral pleura because the bronchial circulation, which supplies the visceral pleura, drains into low pressure pulmonary veins.
Which is thicker: the visceral or parietal pleura?
visceral
Which layer of the pleura has lymphatic stomata? what does this imply?
only the parietal pleura contains lymphatic stomata between mesothelial cells that communicate directly with the lymphatics and provide a drainage system for pleural fluid.
When is pleural symphysis done? why?
in individuals who develop spontaneous pneumothorax, to prevent their formation
What is the pulmonary interstitium? how is it related to the alveolar-capillary interface and the pleural space?
The pulmonary interstitium, which is bordered by the visceral pleura, is a physiologically distinct compartment from the pleural space and contains the alveolar-capillary interface.
What role does pleural fluid serve in health?
mechanical coupling of the lung, chest wall, and diaphragm
Which hydrostatic pressure gradient drives the filtration of blood to make pleural fluid?
systemic capillaries to the microvascular interstitium of the parietal pleura form fluids. Microvascular filtrate is then “pulled” through the mesothelial lining of the parietal pleura into the pleural space by a small pressure gradient (approximately -10 cmH2O) between the parietal pleura interstitium and the subatmospheric pressure of the pleural space.
What creates the negative pressure of the pleural space?
This negative pressure results from a combination of pleural surface pressure (a balance between the opposite recoil pressures of the lung and chest wall) and pleural liquid pressure (which is generated largely by the strong pumping action of the parietal lymphatics).
Congestive heart failure would be expected to affect what part of the Starlings forces, leading to pleural effusion?
increase microvascular hydrostatic pressure
Nephrotic syndrome would be expected to affect which aspect of the starlings forces, leading to pleural effusion?
decreased microvascular oncotic pressure
Malignancy could be expected to affect which aspect of the starlings forces that lead to pleural effusion?
obstruct lymphatic drainage (i.e. obliterating pressure gradients by blocking flow)
What effect would a trapped lung have on the starlings forces that lead to pleural effusion?
decreased pleural space pressure would decrease pressure gradients for drainage
What effect does parapneumonic effusion have on starlings forces, leading to pleural effusion?
increased permeability of capillaries or pleural lining
Does the Lights criteria identifies a pleural effusion as an exudate or a transudates?
exudates
What is the pleural fluid total protein/serum total protein cut off for classification of an exudate?
> 0.5
what is the lactate dehydrogenase cut off for the classification of an exudate?
> 0,6
What is the cut off for pleural fluid LDH v. serum LDH to classify an effusion as an exudate?
Pleural fluid LDH > 2/3 of the upper normal value of serum LDH
Why do the Lights criteria focus on the protein concentration of pleural fluid?
concentration of protein in the pleural fluid is a rough estimate of the leakiness of the pleural membrane to protein
What does LDH tell us about the pleural effusion that is important?
The pleural fluid LDH correlates with the amount of inflammation in or near the pleura.
Under what conditions do exudative effusions occur?
increases in pleural fluid protein and LDH (i.e. exudative effusions) occur when the pleural membrane is leaky or inflamed
Under what conditions do transudative effusions occur?
low pleural fluid protein and LDH (i.e. transudative effusions) occur when alterations of the Starling hydrostatic forces cause increased fluid formation across a normal membrane
What is a clinical scenario in which the Light’s criteria could give a false positive result for exudate?
patients with known heart failure who have been treated with diuretics, which increases the protein content of the effusion creating a “false positive” exudate. The best of these criteria is a pleural fluid cholesterol value of > 45 mg/dl defines an exudate.
What do we look at to determine if the Lights criteria has given a false positive for exudate?
pleural fluid cholesterol value of > 45 mg/dl defines an exudate
- Congestive heart failure
- Liver Cirrhosis
- Nephrotic syndrome
- Atelectasis
- Hypothyroidism
- Pulmonary embolus
- Peritoneal Dialysis
Are these transudative effusions or exudative?
transudative
Congestive heart failure: transudative or exudative?
transudative
liver cirrhosis: transudative or exudative?
transudative
nephrotic syndrome: transudative or exudative?
transudative
atelectasis: transudative or exudative?
transudative
hypothyroidism: transudative or exudative?
transudative
pulmonary embolus: transudative or exudative?
transudative
peritoneal dialysis: transudative or exudative?
transudative
- Neoplasm
- Infections in the pleural space
- Infections abutting the pleural space
- Pulmonary embolus
- Collagen vascular disease
- Drug induced pleural disease
- Gastrointestinal disease (esophageal perforation, pancreatitis)
- Post-pericardotomy or post-myocardial infarction syndrome
- Uremia
- Asbestos exposure
- Meig’s Syndrome (ovarian tumor + ascites + pleural effusion)
- Yellow nail Syndrome (pleural effusions + lymphedema + yellow nails)
- Iatrogenic injury
- Hemothorax
- Chylothorax
Transudative or exudative?
Exudative
What are possible symptoms of a large pleural effusion?
nonproductive cough and chest discomfort
What does pleuritic chest pain indicate when evaluating a pleural effusion?
inflammation of parietal pleura as only the parietal pleura is innervated
What is the test of choice for confirming a pleural effusion?
bedside ultrasound
When do pleural effusions require drainage?
large and symptomatic or infection
Is the pH of pleural fluid typically higher or lower than the serum?
usually higher due to bicarb transport
What do low pH pleural effusions indicate?
Low pH pleural effusions are seen most commonly in infected parapneumonic effusions (pleural effusions adjacent to a pneumonia)
can also occur in patients with malignancies with extensive pleural involvement, and esophageal perforation
When is a pH of less than 7.2 an indication for chest tube drainage?
In the setting of pneumonia accompanied by an exudative effusion (parapneumonic effusion), a pH of less than 7.2 is generally considered an indication for chest tube drainage.
When are low glucose pleural effusions seen?
Low glucose effusions are seen with infection, malignancy with extensive pleural involvement, and rheumatoid arthritis
What is the number of thoracenteses that hae good sensitivity for detecting malignancies?
2
A pleural effusion with a predominance of polymorphonuclear cells indicates what etiology?
infection
a pleural effusion with a predominance of lymphocytes indicates what etiology?
a predominance of lymphocytes can be seen with malignancy and tuberculous or fungal effusions
What does a hemothorax usually indicate?
trauma
What is the hematocrit or RBC count that defines a hemothorax?
> 50% compared to peripheral blood
What is empyema?
pleural effusion with purulence
What is required for the diagnosis of empyema?
chest tube or surgical drainage
Are elevated adenosine deaminase levels in pleural effusions specific or sensitive for tuberculous effusions?
specific but not senstivie
At what point does air stop flowing from the lungs to the pleural space during a pneumothorax?
When the lung is punctured, air continues to flow into the pleural space until the inspiratory pleural pressure approaches atmospheric pressure and flow ceases.
Define a tension pneumothorax. At what point does it compromise right heart filling?
ball valve type holes in the lung which limit expiratory flow out of the pleural space, leading to very high positive pleural pressures.
When pressures equal right atrial pressure, filling is impaired
Among what population of patients are tension pneumothoraces common?
mechanically ventilated patients
Are pleural effusions or pneumothoraces symptomatic?
pneumothorax
What are the three types of pneumothorax that require chest tube drainage?
- large
- increasing in size
- develop during mechanical ventilation
- Name the 3 Light’s Criteria (meeting any one of the following means you have an exudative effusion)
a. Pleural fluid total protein/serum total protein >0.5
b. Pleural fluid lactate dehydrogenase (LDH)/serum LDH > 0.6
c. Pleural fluid LDH > 2/3 of the upper normal value of serum LDH
Name the 2 most common causes of a transudative pleural effusion
a. Congestive heart failure (by far the most common)
b. Cirrhosis
How can a pneumothorax lead to cardiac arrest?
If a hole in the lung functions as a ball valve limiting expiratory flow out of the pleural space, very high positive pleural pressures can develop. When these pressures exceed right atrial pressure, venous return (and subsequently cardiac output) falls leading to cardiac arrest. This life-threatening condition is called a tension pneumothorax and requires immediate drainage of the pleural space.
