Diagnosing pneumothorax with ultrasound

Ultrasound is more sensitive than a supine chest X-ray for pneumothorax. Air rises, so in a patient lying flat you scan the anterior chest first.

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The signs, in order

Absent lung sliding at the pleural line.
No B-lines (a single B-line rules out pneumothorax at that spot).
Barcode sign in M-mode instead of the seashore sign.
Lung point: the edge where sliding lung meets the pneumothorax — highly specific.

False positives

Absent sliding also occurs with apnoea, right mainstem intubation (on the left), pleurodesis or adhesions, and severe ARDS or COPD. Look for a lung point before committing in a stable patient.

Real scans

Lung point (clip). Clip showing the lung point: the place where sliding lung meets non-sliding pneumothorax, moving across the screen with breathing. Best appreciated in motion. Gillman L, Kirkpatrick A · CC BY 2.0 · source

Barcode / stratosphere sign (M-mode, pneumothorax) — M-mode in pneumothorax: horizontal lines all the way down because the lung is not sliding. Only the M-mode strip is shown. Very small image (231 px). — **Barcode / stratosphere sign (M-mode, pneumothorax).** M-mode in pneumothorax: horizontal lines all the way down because the lung is not sliding. Only the M-mode strip is shown. Very small image (231 px). schomynv · Public domain · source

Seashore sign (M-mode) — In M-mode, the motionless chest wall makes straight lines ('waves') and the sliding lung below the pleura makes a grainy 'sand' pattern: normal lung sliding. — **Seashore sign (M-mode).** In M-mode, the motionless chest wall makes straight lines ('waves') and the sliding lung below the pleura makes a grainy 'sand' pattern: normal lung sliding. Tinss · CC BY-SA 4.0 · source

Learn this with your hands. Sonoduck gives you a 3D patient, a probe and a coach that tells you what to do. Free to start, no signup.

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FAQ

Can ultrasound size a pneumothorax?

Roughly — the more lateral the lung point, the larger the pneumothorax — but not precisely.

Which probe should I use?

Linear for the anterior pleural line; curvilinear is fine too.

Related guides

Lung sliding on ultrasoundWhat lung sliding is, how to see it with a linear probe, the bat sign, seashore sign, and why absent sliding suggests pneumothorax. Try it in a live simulator.
A-lines vs B-linesThe difference between A-lines and B-lines on lung ultrasound, how many B-lines are abnormal, and what they mean — with real images and a live simulator.
The FAST exam, explained by actually doing itHow to perform a FAST exam: RUQ, LUQ, pelvic and subxiphoid views, what a positive scan looks like, common pitfalls — with a live ultrasound simulator you can try.

Educational content for learners; follow local protocols and supervision. Simulated images are generated by Sonoduck’s physics model; real images are credited individually.