This is a PA, slightly lordotic chest film, although there is some failure to fully abduct the scapula. The left hemithorax is markedly hyperlucent; there is some widening of the interspaces with a depressed diaphragm and air under the hea shadow. There is a large bandlike shadow extending from the apex of the left lung down to the bottom of the hea with silhouetting of the left cardiac border. This represents a total lung collapse with atelectasis; however, some of the air totally surrounds the lung with hyperlucency around the aoic knob. Most pneumothoraces usually show a sharp edge differentiating the free air in the pleural space from the normal pulmonary parenchyma, with a line representing the pleural surfaces. In this paicular case, because of marked collapse with circumferential air, one does not see the sharp line and observes bilateral edges, i.e., differences in contrast between a more radiodense and radiolucent back-ground. The very sharp edge along the left hea border represents the contrast between the collapsed lung and the pleural space and is called the visceral pleural line. The chest wall appears irregular along the level of lateral 6th to 7th ribs, probably representing a rib fracture. The acute onset of severe shoness of breath and left-sided chest pain suggests concurrent pleural disease as pa of the differential diagnosis. This is confirmed by the chest x-ray showing a left-sided pneumothorax. Patients with COPD and/or bullous disease have chronic symptoms. With an acute exacerbation of COPD, the chest x-ray is helpful in distinguishing a pneumothorax vs. pneumonia. On physical exam, patients with pneumothorax present with absent breath sounds and hyperresonance on the side of the pneumothorax. The other physical findings mentioned are not characteristic of pneumothorax. Management of a symptomatic patient with a large pneumothorax is by inseion of a chest tube.