Why are pneumothoraces more obvious on expiratory films?
The main reason is that as the lungs are emptied they slightly increase in density (less air, same amount of lung tissue, in a smaller volume) and reduce in size. The pneumothorax thus appears more lucent by comparison and larger.
What would the treatment of this pneumothorax be?
Observation both clinically and with serial chest x-rays. As long as the patient remains well and the pneumothorax does not enlarge, it can be watched, and the vast majority of small pneumothoraces of this size will spontaneously resolve.
Inspiratory and expiratory films have been obtained. Left apical pneumothorax is confirmed best seen on the expiratory view. The apex of the partially collapsed lung reaches the sixth posterior rib.