Fig. 14

Pneumothorax. a The transducer is placed in a longitudinal axis over an intercostal space at the anterior surface of the chest; this is the area where free air in the chest cavity is expected to be located. b If pneumothorax is present the pleura-line only represents the parietal pleura, therefore the motion of the visceral pleura cannot be visualised and subsequently lung sliding is absent. c In M-mode the lack of lung sliding will appear as the “stratosphere sign”, a pattern only consisting of horizontal lines