Pneumothorax

Why does the contra lateral lung appears more dense?

Blood flow dramatically decreases on the side of pneumothorax. Most of the cardiac output is diverted to normal side thus increasing the interstitial vascular markings.

What would be the radio density of the partially atelectatic "normal" lung

One would expect the partially atelectatic lung to be more denser than normal lung. In reality it is of the same radiolucency, because the blood flow decreases. If the atelectatic lung appears more dense it is likely that there is a disease process. (mass, interstitial or alveolar) in the lungs. Of course the lug will be radio dense once it is completely atelectatic.

What are the true signs of tension pneumothorax?

I do not like making decisions about tension from grading pneumothorax. I like to classify pneumothorax as symptomatic or symptomatic. We can observe and expect the pneumothorax to resolve spontaneously in asymptomatic pneumothorax, however large it is. Symptomatic pneumothorax requires chest tube evacuation. A small pneumothorax in a patient with emphysema, ARDS will require chest tube evacuation.

Judge tension by hemodynamic parameters and not by chest x-ray.

Progressive shift of mediastinum and concave diaphragm are the only sure signs of tension. Size of pneumothorax and size of henithorrax are not.

Why is the hemi thorax larger on the side of pneumothorax?

The FRC position of chest wall is the result of balance of forces of lung recoil and chest wall forces. In pneumothorax there is loss of pleural negative pressure and the chest wall is released to rest at total lung capacity position. This is not due to tension.

Does shift of mediastinum mean tension?

Mediastinum is in middle because the pleural negative pressure is the same on both sides. In pneumothorax there is loss of negative pressure on the side of pneumothorax. The normal side pulls the mediastinum towards its side. Thus the initial shift of mediastinum is not due to tension. There will be progressive shifting of mediastinum with tension pneumothorax.

Can you recognize blebs on the side of pneumothorax?

Yes. It is the best time to look for lung surface blebs. They become visible because of contrast with air in the pleural cavity. Recognition also supports that there is no tension in pleural space. Blebs are extremely compliant and would be compressed if there is tension.