Ch.8 - Recognizing Pneumothorax, Pneumomediastinum, Pneumopericardium, and Subcutaneous Emphysema

Question 1

Beware of the pitfalls that resemble pneumothoraces:

Answer 1

1. Bullae.
2. Skin folds.
3. Medial border of the scapula.

Question 2

Simple pneumothoraces:

Answer 2

Those with NO SHIFT of the heart or mobile mediastinal structures - Most pneumothoraces are simple.

Question 3

Tension pneumothoraces (usually associated with cardiorespiratory compromise):

Answer 3

Produce a shift of the heart and mediastinal structures away from the side of the pneumothorax by virtue of a check valve mechanism that allows air to enter the pleural space but not leave.

Question 4

Most pneumothoraces are … in etiology.

Answer 4

Traumatic.

Either accidental or idiopathic.

Question 5

CXR or CT to estimate the size of the pneumothorax?

Answer 5

CT is better.

Most important assessment to be made is the clinical status of the patient.

Question 6

Besides the conventional upright CXR, other ways to diagnose a pneumothorax:

Answer 6

1. Expiratory exposures.
2. Decubitus views.
3. Delayed images.
   CT remains the most sensitive test for detecting small pneumothoraces.

Question 7

Spontaneous pneumothoraces:

Answer 7

Most often occur as a result of rupture of a small apical, subpleural bleb; they most often occur in younger men.

Question 8

Pulmonary interstitial emphysema:

Answer 8

Results from an increase in the intralveolar pressure that leads to rupture of an alveolus and dissection of air back towards the hila along the bronchovascular bundles.
It is frequent difficult to visualize.

Question 9

Pneumomediastinum:

Answer 9

Can occur when air tracks back to the mediastinum from a ruptured alveolus or from perforation of an air-containing viscus such as the esophagus or trachea.
–> It can produce the continuous diaphragm sign on a frontal CXR.

Question 10

Pneumopericardium is usually due to:

Answer 10

Direct penetration of the pericardium rather than dissection of air from a pneumomediastinum.
–> It can be difficult to differentiate from a pneumomediastinum.

Question 11

Key to differentiate pneumopericardium from pneumomediastinum:

Answer 11

Pneumopericardium does NOT extend above the roots of the great vessels, whereas pneumomediastinum does.

Question 12

We must be able to identify the … to make the definitive diagnosis of pneumothorax.

Answer 12

The visceral pleural line.

Question 13

Pitfall about pneumothorax?

Answer 13

Pleural adhesions may keep part, but not all, of the visceral pleura adherent to the parietal pleura, even in the presence of pneumothorax.

Question 14

Is absence of lung markings alone sufficient to diagnose pneumothorax?

Answer 14

NO - Nor is the presence of them enough to exclude pneumothorax.

Question 15

What is, by definition, an indication that a pneumothorax is present?

Answer 15

The presence of an AIR-FLUID interface in the pleural space.

Question 16

Supine position - Air in a relatively large pneumothorax?

Answer 16

May collect ANTERIORLY + INFERIORLY in the thorax –> Displacing the costophrenic sulcus inferiorly while, at the same time, producing INCREASED LUCENCY OF THAT COSTOPHRENIC SULCUS = Deep sulcus sign.

Question 17

Pitfall 1 in pneumothorax?

Answer 17

Absence of lung marking mistaken for a pneumothorax.

Question 18

The simple absence of lung markings is NOT SUFFICIENT to warrant the diagnosis of pneumothorax as other diseases produce such a finding:

Answer 18

1. Bullous disease of the lung.
2. Large cysts in the lung.
3. Pulm. embolism.

Question 19

How can pulmonary embolism result in the absence of lung markings?

Answer 19

Lack of perfusion and hence a decrease in the number of vessels visible in a particular part of the lung = Westermark sign of oligemia.

Question 20

Pitfall 1 about pneumothorax - Solution?

Answer 20

Look at the contour of the structure you believe is the visceral pleural line.
–> Unlike the margin of a bulla, the visceral pleural line will be CONVEX OUTWARD toward the chest wall and will parallel the curve of the chest wall.

Question 21

Pitfall 2 about pneumothorax:

Answer 21

Mistaking a SKIN FOLD for a pneumothorax.

Question 22

Solution about pitfall 2?

Answer 22

Unlike the thin, white line of the visceral pleura, skin folds produce a relatively THICK, WHITE BAND of density.

Question 23

Pitfall 3 about pneumothorax?

Answer 23

Mistaking the medial border of the scapula for a pneumothorax.

Question 24

5 signs to look for in pneumothorax:

Answer 24

1. Visualization of the visceral pleural line - a MUST for the diagnosis.
2. Convex curve of the visceral pleural line paralleling the contour of the chest wall.
3. Absence of lung markings distal to the visceral pleural line (most times).
4. The DEEP SULCUS SIGN of an inferiorly displaced costophrenic angle seen on a supine chest.
5. The presence of an air-fluid interface in the pleural space.

Question 25

What is the vanishing lung syndrome?

Answer 25

On rare occasions, the bullae can grow so large as to render the hemithorax seemingly devoid of visible lung tissue.

Question 26

Tension pneumothorax may lead to?

Answer 26

Cardiopulmonary compromise by impairing venous return to the heart.

Question 27

Causes of pneumothorax?

Answer 27

1. Spontaneous.
2. Traumatic (MCC either accidental or iatrogenic).
3. Diseases that DECREASE lung compliance - eg eosinophilic granuloma.
4. Diseases that stiffen the lung. –> Hyaline membrane in infants.
5. Rupture of an alveolus or bronchiole eg asthma.

Question 28

What has essentially replaced expiratory and decubitus views of the chest for the diagnosis of pneumothorax?

Answer 28

CT of the chest.

Question 29

Decubitus CXR may be helpful in demonstrating a pneumothorax in?

Answer 29

An infant.

Question 30

After the alveolar rupture, the extraalveolar air may take one of two paths:

Answer 30

1. If the alveolus is in close proximity to a pleural surface, the air may burst outward into the pleural space –> Pneumothorax.
2. The air can track backward along the bronchovascular bundles in the lung to the MEDIASTINUM –> Then, into the neck and out to the subcutaneous tissues of the chest and abdominal wall.
   - -> Air can eventually track down into the abdomen as well as retroperitoneum.

Question 31

How large is the pneumothorax? (4)

Answer 31

1. Size measurements of pneumothoraces on CXR correlate POORLY with CT scans of their actual size.
2. Correlation is poor between the size of the pneumothorax and the degree of clinical impairment.
3. The 2cm rule: If the distance between the lung margin and the chest wall at the apex is Most important.

Question 32

About … in … patients with pulmonary interstitial emphysema will develop pneumomediastinum.

Answer 32

1/3. Most will develop pneumothorax.

Question 33

Radiographic findings of pneumomediastinum:

Answer 33

1. Linear, streaklike lucency associated with a thin, white line paralleling the left heart border.
2. Streaky air outlining the great vessels.
3. Linear streaks of air parallel to the spine in the upper thorax extending into the neck.
4. Continuous diaphragm sign.

Question 34

Continuous diaphragm sign?

Answer 34

Seen in PNEUMOMEDIASTINUM - Air can outline the CENTRAL PORTION of the diaphragm BENEATH the heart.

Question 35

You must identify the … to diagnose pneumothorax.

Answer 35

visceral line.