04/20/2026
Seashore or barcode? Your M-mode answer to one of the most important yes-or-no questions in lung ultrasound.
If you see a granular “sandy” pattern below the pleural line, that’s the seashore sign – lung sliding is present, and pneumothorax is unlikely.
If everything turns into parallel horizontal lines, that’s the barcode (stratosphere) sign – no sliding, and now pneumothorax moves way up your differential.
How to check it right:
Use a linear probe (curvilinear or phased are just fine during an eFAST scan) for the best pleural detail. Place it in the anterior chest (2nd–4th intercostal space, midclavicular line) with the probe between the ribs. Find the pleural line, then drop into M-mode.
Reality check:
Barcode sign ≠ automatic pneumothorax. No sliding can also be seen with apnea, mainstem intubation, fibrosis, or pleurodesis.
Images from: Nürnberg, D., Chammas, M. C., Gilja, O. H., Sporea, I., & Sirli, R. (Eds.). (2021). WFUMB course book (1st ed.). World Federation for Ultrasound in Medicine and Biology.