The medial pneumothorax.

The intrapleural air of a pneumothorax may largely collect medial to the anterior aspect of the lung in supine infants. The mechanical basis for this phenomenon is presented with supporting experimental evidence. This distribution of intrapleural air poses problems in recognition of the pneumothorax radiographically, in differentiation of the pneumothorax from pneumomediastinum, in estimation of the true volume of intrapleural air, and in the proper placement of drainage tubes. The importance of horizontal-beam lateral radiographs and of careful attention to the position of intrapleural tubes is emphasized, especially in supine, immobile newborns.