Air: subcutaneous emphysema vs pneumothorax

Images and text Genevieve Carbonatto

A 66  year old presents to the Emergency Department after a fall onto her right chest wall. She had slipped in her bedroom and landed backwards onto a cabinet in her bedroom . She is in great pain on arrival to ED.

This is her ultrasound where there is clinically subcutaneous emphysema

Note that the Bat sign is not visible. There is no  pleural line nor  rib shadows visible. The dirty shadow is due to the presence of air in  the subcutaneous tissues.

This is her lung ultrasound taken close to the sternum at the highest point of her chest

Note that one rib shadow is visible, but there is no lung sliding. This is the pneumothorax. The pleural line is visible.

Just lateral to the area of pneumothorax, this is her lung ultrasound.

Here the Bat sign is visible, and there is decreased lung sliding, but lung sliding does occur. If you look below the pleural line there is a clear distinction between the area above the pleural line (Key space) and below (Merlin space). M mode through this  shows a “lung pulse” first descibed by Lichtenstein in 2003 (1) showing transmission of the cardiac pulsations to the pleural line. The presence of the lung pulse safely rules out pneumothorax in 93% of cases of patients with absent lung sliding . (1)

This is her Xray

Teaching point: Lung ultrasound should be formalised. Always examine the lungs with the probe in the longitudinal position, in this way the “bat sign”  (rib shadows and pleural line) is always visible. If you are not seeing lung sliding then do an M mode. If a lung pulse is present then you  can say with 93% confidence that a pneumothorax is not present. 


  1. Lichtenstein DA, Lascols N, Prin S, Mezière G. The “lung pulse”: An early ultrasound sign of complete atelectasis. Intensive Care Med 2003;29:2187-92.
  2. J Anaesth Clin Pharmacology REVIEW ARTICLE Year : 2016 | Volume : 32 | Issue : 3 | Page : 288-297 Intraoperative lung ultrasound: A clinicodynamic perspective ; Amit Kumar Mittal, Namrata Gupta



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