Supine chest radiograph of a neonate illustrates the deep sulcus sign with abnormal deepening and lucency of the left lateral costophrenic angle (*). Findings on right lateral decubitus chest radiograph (not shown) confirmed the presence of a pneumothorax on the left side.
Supine chest radiograph demonstrating signs of a right supine pneumothorax despite the presence of a chest drain. There is abnormal lucency over the lower right chestand upper abdomen. Subpulmonic air (white asterisk) out-lines the inferior surface of the lung with sharp delineationof the right hemidiaphragm. The right side of the medias-tinum is unusually well defined (black arrows) because of theadjacent air rather than normal aerated lung. The deepsulcus sign is also seen (white arrow).Detection of Pneumothorax in the Supine Subject
In the supine position, air within the pleural space rises to the highest point in the hemithorax, which is in the area of the hemidiaphragm. This makes it less likely that one will see the classic visceral pleural line -- indeed, supine films are relatively insensitive in detecting pneumothoraces (50 - 70 %). One may increase the pickup rate with the use of expiratory radiographs or with CT of the chest. However, it is also useful to learn the following secondary signs of pneumothorax on the supine radiograph:
*deep sulcus sign
*relative lucency in the hypochondrial（季肋部） region or the entire hemithorax;
*depression of an ipsilateral hemidiaphragm;
*double-diaphragm appearance due to air outlining of the anterior costophrenic angle and aerated lung outlining the diaphragmatic dome;
*improved sharpness of the cardiomediastinal border due to anteromedial collection of air, which may appear as a lucency;
*increased sharpness of the pericardial fat pads;
*visible inferior edge of a collapsed lower lobe or of the undersurface of the heart due to air in the pleural space;
*band of air in the minor fissure bounded by two visceral pleural lines;
*visible lateral edge of the right middle lobe due to medial retraction in the presence of anterior pneumothorax.
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