In FAST/Trauma ultrasound, the thoracic sliding lung sign is a crucial indicator of pneumothorax, reflecting the normal movement of the visceral pleura against the parietal pleura during respiration. This “lung sliding” appears as a shimmering, granular motion or “ants marching” pattern on M-mode ultrasound, signifying no air is trapped between the lung and chest wall. Its presence effectively rules out a pneumothorax at the site of probe placement, making it vital for rapid assessment in emergency settings.
Conversely, the absence of this sliding sign, coupled with a “barcode” or “stratosphere” sign on M-mode, strongly suggests a pneumothorax, prompting further investigation. This simple, yet powerful, ultrasound finding is fundamental for clinicians utilizing the extended Focused Assessment with Sonography for Trauma (E-FAST) exam to quickly diagnose life-threatening conditions without relying on ionizing radiation.
