23 Pleura
The pleura is a strong reflector of ultrasound waves. Comet-tail artifact, indicating reverberation of sound waves, is observed deep to the pleural line on ultrasound scans.1 Another characteristic feature of pleura with ultrasound imaging is “lung sliding.”2 The pleural line moves to and fro with ventilation. This motion is greatest at the base of the lung and least at the apex because most of the translational motion of the lung is generated by descent of the diaphragm. Both comet-tail artifact and lung sliding are eliminated when pneumothorax is present.3
FIGURE 23-1 Comet-tail artifact observed deep to the pleural line during supraclavicular block of the brachial plexus.
1 Thickman DI, Ziskin MC, Goldenberg NJ, et al. Clinical manifestations of the comet tail artifact. J Ultrasound Med. 1983;2:225–230.
2 Lichtenstein DA, Menu Y. A bedside ultrasound sign ruling out pneumothorax in the critically ill: lung sliding. Chest. 1995;108:1345–1348.
3 Lichtenstein D, Meziere G, Biderman P, et al. The comet-tail artifact: an ultrasound sign ruling out pneumothorax. Intensive Care Med. 1999;25:383–388.
