Pleural Disease

Question 1

Pleura anatomy cartoon

Answer 1

Question 2

Stomata

Answer 2

Openings between mesothelial cells on the parietal, but not visceral, pleural surface. Each stoma leads to lymphatic channels, allowing a passageway for liquid from the pleural space to the lymphatic system.

Question 3

The blood supply of the pleura comes from. . .

Answer 3

. . . the bronchial arteries.

Question 4

Pleural fluid formation and resorption

Answer 4

Formation of fluid is ongoing primarily from the parietal pleural surface, and fluid is resorbed through the stomata into the lymphatic channels of the parietal pleura

Question 5

Pleural volume vs daily formation/resorption equilibrium

Answer 5

In the average healthy adult, the pleural volume is ~10 mL.

However, the daily formation and resorption of pleural fluid is 15-20 mL. Thus, the pleura is constantly cycling fluid at the rate of 1.5-2x its fluid load per day.

Question 6

Pleural fluid exchange diagram

Answer 6

Question 7

Starling Equation

Answer 7

Question 8

How fluid travels at the parietal vs visceral pleura

Answer 8

At the parietal pleura, fluid is driven by hydrostatic pressure from the pleural capillaries into the pleural space.

At the visceral pleura, fluid is driven by hydrostatic pressure from the visceral pleural capillaries somewhat into the pleural space, but primarily into pulmonary venous circulation.

Remember: At the parietal pleura, systemic arterial blood (~80-120 mmHg) drains into the systemic venous circulation (~40-50 mmHg). At the visceral pleura, systemic arterial blood drains into the pulmonary venous circulation (~8-10 mmHg).

Thus, most of the fluid in the pleura comes from the parietal pleura, because it has a greater driving pressure forcing fluid into the pleural space (about 9 cm H₂O).

Question 9

Respiratory pleural pump

Answer 9

The movement of respiration is thought to help drive pleural fluid through stomata into lymphatic ducts, which are then sealed off with one-way valves.

Question 10

The essential problem of pleural effusion

Answer 10

A tilted equilibrium: The rate of pleural fluid accumulation exceeds the homeostatic rate of pleural fluid resorption.

This may be the result of changes in relative permeability (K and σ) or changes in the relative pressures (P and π).

Question 11

Most common diseases that cause pleural effusion through a change in K and σ

Answer 11

• Inflammation
• Neoplasty

In both of these cases, the increased permeability is termed an exudate due to its high protein content

Question 12

Most common diseases that cause pleural effusion through a change in P and π

Answer 12

• Hypertension
• Congestive heart failure
• Hypoproteinemia (may be secondary to cirrhosis)

In these cases, the fluid is protein-poor, and is thus termed a transudate.

Question 13

Pleural effusion secondary to lymphatic disease

Answer 13

Blockage of lymphatic ducts that drain the pleura can result in a fluid backup, increasing lymphatic pressure and thus leaving fluid stuck in the pleura.

Question 14

As a rule of thumb, exudation implies ___ where as transudation implies ___.

Answer 14

As a rule of thumb, exudation implies primary pathology of the pleura where as transudation implies secondary pathology of the pleura to some other disease process.

Question 15

Why is pulmonary hypertension such a big contributer to pleural effusions?

Answer 15

Because it makes the visceral pleura start to participate in pleural fluid accumulation!

Normally the visceral pleura contributes very little fluid to the pleura due to its drainage into low-pressure pulmonary circulation. However, if pulmonary pressure increases, excess fluid will readily drain into the relatively low pressure pleural space.

Question 16

Parapneumonic effusion

Answer 16

A pleural effusion caused by a pneumonia that extends to the pleural space. Histamine, prostaglandins, cytokines, and other mediators spill over and cause leakiness in the vessels leading to the pleura as well as the lung parenchyma, resulting in an effusion.

Question 17

Empyema thoracis

Answer 17

Pus in the pleural space

Question 18

Pleural effusion second to pancreatitis

Answer 18

Pancreatitis can lead to ascites in the abdomen. This fluid can then travel through the lymphatics draining the diaphragm and end up in the pleura, through a circuitous and unintuitive route.

Nevertheless, this is not uncommonly observed. So be aware, if your patient has pancreatitis leading to acsites, they may be at risk of pleural effusion.

Question 19

Pleuritic chest pain

Answer 19

Sharp pain aggravated by respiration and sometimes hard to localize

Question 20

On physical exam, pleural fluid is ___ to percussion, pulmonary fluid is ___ to percussion, and pneumothorax is ___ to percussion.

Answer 20

On physical exam, pleural fluid is dull to percussion, pulmonary fluid is dull to percussion, and pneumothorax is hyperresonant to percussion.

Question 21

Major finding of inflammatory pleural effusion on physical exam

Answer 21

Pleural rub on auscultation

Question 22

Loculations

Answer 22

Fibrous bands of tissue that may form in long-standing pleural effusions.

These bands of tissue may straddle the pleural fluid in, making it appear as though it is not quite following gravity downward the way one may expect. Ultrasonography is extremely helpful in these cases.

If loculation has occurred, these fibrous bands must be removed for adequate drainage of the fluid.

Question 23

___ allows determination of the cellular and chemical characteristics of pleural effusion fluid

Answer 23

Thoracentesis allows determination of the cellular and chemical characteristics of pleural effusion fluid.

Question 24

Pleurodesis

Answer 24

In some cases with recurrent large effusions causing dyspnea, the fluid is initially drained with a tube passed into the pleural space, and an irritating agent (e.g., talc or a tetracycline derivative) is instilled via the tube into the pleural space to induce inflammation and cause the visceral and parietal pleural surfaces to become adherent (fibrosis).

Question 25

Common causes of pneumothorax

Answer 25

1. Trauma
2. Iatrogenesis
3. Tear of a cyst/bleb/bulla bordering the visceral pleura

Question 26

Most common cause of pneumothorax in AIDS patients

Answer 26

Pneumocystis jiroveci

Presumably because of necrosis or cyst formation adjacent to the visceral pleura

Question 27

Tension pneumothorax is a not uncommon complication of ____.

Answer 27

Tension pneumothorax is a not uncommon complication of mechanical ventilation.

Question 28

Tension pneumothorax

Answer 28

Pneumothorax with pressure greater than 1 atm

This tension within the pleural space is believed to occur as a result of a “one-way valve” mechanism by which air is free to enter the pleural space during inspiration, but the site of entry is closed during expiration

Sufficiently high pressures will shift mediastinal contents to the other side.

Question 29

In tension pneumothorax, venous return to the heart will ___.

Answer 29

In tension pneumothorax, venous return to the heart will decrease.

Question 30

For most cases of pneumothorax, after the site of entry into the pleural space is closed, the air is ___.

Answer 30

For most cases of pneumothorax, after the site of entry into the pleural space is closed, the air is spontaneously resorbed

However, it can be removed faster through medical intervention if necessary (ex, catheterization)

Question 31

If ___ is administered to the patient with a pneumothorax, the process of resorption can be hastened

Answer 31

If pure O₂ is administered to the patient with a pneumothorax, the process of resorption can be hastened

In arterial blood, most of the nitrogen is replaced by O2. As a result, Pn2 in the capillary blood surrounding the pneumothorax becomes quite low, and the gradient for resorption of nitrogen from the pleural space has been increased considerably

Question 32

Pneumothorax is ___thorax

Answer 32

Pneumothorax is Nitrothorax

It’s! All! Nitrogen!

Question 33

Hydropneumothorax

Answer 33

When fluid and air are both in the pleural space.

Fluid no longer appears as a meniscus tracking up along the lateral chest wall. Rather, the fluid falls to the most dependent part of the pleural space and appears as a liquid density with a perfectly horizontal upper border

Question 34

___ because of a tension pneumothorax is an emergency, and a needle, catheter, or tube must be inserted immediately to relieve the pressure.

Answer 34

Hemodynamic compromise because of a tension pneumothorax is an emergency, and a needle, catheter, or tube must be inserted immediately to relieve the pressure.

Question 35

How do chest wall volume, lung volume, and airway resistance change in pneumothorax?

Answer 35

Chest wall volume up

Lung volume down

Airway resistance up

Question 36

Normal total protein and LDH for pleural fluid

Answer 36

45% of systemic concentrations or less

Question 37

Nephrotic syndrome

Answer 37

Characterized by high levels of protein excretion in the urine. As a result, patients with nephrotic syndrome often have hypoalbuminemia and edema, possibly including pleural effusion transudate.

Question 38

Pancreatitis produces a pleural ___.

Answer 38

Pancreatitis produces a pleural exudate.

Question 39

When should you tap a pleural effusion?

Answer 39

Effusions should generally be tapped early in the clinical course, especially if etiology is uncertain

Question 40

Causes of Pleural Effusion - Transudates

Answer 40

Question 41

Causes of Pleural Effusion - Exudates

Answer 41

Question 42

Light’s Criteria

Answer 42

A pleural exudate is present if any of the following criteria are met:

• Pleural fluid / serum protein >0.5
• Pleural fluid / serum LDH >0.6
• Pleural fluid LDH >2/3 upper limit of normal serum value