The patient has tension pneumothorax, as evidenced by distended neck veins and absent breath sounds. Increased intrathoracic pressure interferes with venous return to the heart, resulting in shock. Immediate management should be insertion of a large-bore needle in the left second intercostal space, followed by insertion of a chest tube. In a trauma patient, venous access should be achieved by inserting two large-bore (16-gauge) angiocatheters in the cubital veins. Insertion of a central venous line on the right side should not be done, because it carries the risk of producing pneumothorax in the opposite side.