Fig. 2

Volumetric assessment of pneumothorax on a frontal chest radiograph. This is performed using the formula: pneumothorax % = 4.2 + [4.7 (A + B + C)]. ‘A’ represents the distance from the lung to the cupola. ‘B’ represents the distance from the upper mid collapsed lung to the chest wall and ‘C’ represents the distance from the lower mid collapsed lung to the chest wall. If this number is greater than 25 %, chest tube drainage is recommended