Frontal view of the chest shows large pneumothorax on the left causing collapse of the left lung and shift of the mediastinum to the right. Note the absence of any normal blood vessels in the region of the pneumothorax. The marked shift of the mediastinum indicates the the pneumothorax is generating high pressure, i.e., a tension pneumothorax. This requires emergent decompression of the pneumothorax by percutaneous needle or tube insertion.