Pneumothorax occurs when air leaks from inside of the lung to the space between the lung and the chest wall. The lung then collapses. The dark side of the chest (right side of the picture) is filled with air that is outside of the lung tissue.
Update Date 11/11/2008
Updated by: Robert A. Cowles, MD, Assistant Professor of Surgery, Columbia University College of Physicians and Surgeons, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.