2013-09-19 Pleural Diseases

Question 1

Describe the pleura

• -gross anatomy
• -histology
• -blood supply
• -lymphatics
• -innervation

Answer 1

gross: contiguous with parietal (lining inside of ribs/chest) and visceral (lining lungs themselves and going into the interlobar fissures) component
—create potential space in between (pleural space with negative, i.e. subatmospheric, pressure)

histologically:
—A. single layer of mesothelial cells
—B. Loose connective tissue
—C. Elastic tissue
—D. Areolar layer – Lymph and vascular located here. Stomata feed into lacunae.

Blood supply: both likely supplied from systemic blood supply

lymphatics: rich lymphatics; parietal side w/ lymphatic stomata for drainage
innervation: parietal side has pain afferents via intercostal and phrenic nn.; visceral side has no pain receptors

Question 2

Explain the normal movement of fluid across the pleural space

Answer 2

While theres is only a few mLs of fluid in the pleural space at any given time, there is a high rate of turnover (>500mL/day) grace à Starling Forces. Normally rate of filtrating is equal to rate of reabsorption (which occurs primary via lymphatic stomata) but can be thrown off in dz.

Question 3

Describe Starling’s law and explain how it relates to the pleural space

Answer 3

Starling’s Law states that the balance of fluid inside and outside a vessel is due to the gradients inside to out of:

• -oncotic pressure
• -hydrostatic pressure

Question 4

Describe the pathologic mechanisms by which fluid accumulates in the pleural space

Answer 4

A. Increased hydrostatic pressure:
1. An increase in systemic capillary pressures (right heart failure) causes an increase in the rate of fluid filtration in the capillaries in the parietal pleura. However, because of marked compensatory increases in lymphatic drainage, isolated increases in systemic capillary pressures, at least in humans, rarely cause the development of pleural effusions.
2. An increase in pulmonary capillary pressure (as occurs in left-sided heart failure). In this setting, the pleural fluid appears to represent the movement of lung interstitial fluid across the visceral pleura and into the pleural space. It is not clear why increases in pulmonary capillary pressures produce a greater propensity for the development of pleural effusions than do increases in systemic capillary pressures.
B. Decreased oncotic pressure: e.g., hypoalbuminemia
C. Increased capillary permeability: e.g., pneumonia
D. Increased (i.e. more negative) intrapleural pressure: atelectasis
E. Impaired lymph drainage: obstruction, e.g. mediastinal tumor; prior chest radiation therapy
F. Transdiaphragmatic transport: e.g. cirrhosis

Question 5

Define a pneumothorax and explain how it differs from atelectasis.

Answer 5

pneumothorax and atelectasis are often confused because they share the lay term “collapsed lung

• -atelectasis is a collapse of the alveoli, e.g. after aspirating a peanut
• -pneumothorax is air in the pleural space, compressing the lung from the outside in

Question 6

Describe the physical findings in a patient with a pleural effusion and contrast them with the findings in a patient with pneumonia or a pneumothorax

Answer 6

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Question 7

Define the terms “exudate” and “transudate” and explain how one distinguishes between the two clinically

Answer 7

exudate is fluid that leaked b/c of increased permeability of the capillaries

transudate is fluid that left because of either increased hydrostatic P or decreased oncotic P in the caps, OR a block in the lymphatic drainage

differentiate the two by drawing a sample and using the Light Criteria (See other card)

Question 8

List common diseases that cause a pleural exudate

Answer 8

When the fluid is an exudate, the focus is on processes that directly affect the pleural surface, such as infection or malignancy.

Question 9

List common diseases that cause a pleural transudate

Answer 9

When the fluid is a transudate, the focus is away from the pleural space and instead on processes such as CHF, cirrhosis, nephritic syndrome, etc.

Question 10

What are the sx of pleural effusions? Describe the mechanisms by which pleural effusions cause symptoms in patients

Answer 10

A. Shortness of breath is the most frequent symptom of pleural disease. Surprisingly, the mechanism of dyspnea in pleural effusions is poorly understood.
B. Pain – when pleural inflammation is present, patients may experience pain. When the diaphragmatic pleural surface is involved, pain may be referred to the shoulder
C. Cough – present in some patients, mechanism unclear. May be due to associated atelectasis and stimulation of vagal fibers; at times may be due to underlying disease rather than the effusion per se.
D. There may be symptoms related to the underlying disease responsible for the patient’s pleural effusion.

Question 11

Describe the physiologic effects of pleural effusions and pneumothorax

Answer 11

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Question 12

Define tension pneumothorax and describe and explain the clinical manifestations of a tension
pneumothorax.

Answer 12

A “tension pneumothorax” refers to a situation
where the pressure in the pleural space is increased, usually due to a one-way valve effect. pneumothorax usually represents a medical emergency. (Most common with trauma, patients undergoing mechanical ventilation)

Hemodynamic

Question 13

Describe the diagnostic workup of a patient with a pleural effusion

Question 14

Define the terms “empyema” and complicated parapneumonic effusion

Answer 14

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Question 15

Describe and explain the treatment of a pneumothorax.

Answer 15

Observation (if small, asymptomatic)

Oxygen

Question 16

Describe the radiographic findings in a pleural effusion and a pneumothorax

Answer 16

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