Find the visceral pleural line with no lung markings beyond it — and on a supine film, look at the base, not the apex.
Orient first
- On an ERECT film gas rises to the APEX. On a SUPINE film — most trauma and ICU films — it collects ANTERIORLY and BASALLY, which is why supine pneumothoraces are missed.
- The finding is a visceral pleural LINE with no lung markings peripheral to it. A skin fold has no lung markings on BOTH sides and usually extends beyond the chest wall.
- Tension pneumothorax is a CLINICAL diagnosis. If you see mediastinal shift and a depressed hemidiaphragm, communicate immediately rather than finishing the report first.
Acquire the study
- RADIOGRAPH: erect PA in full inspiration is the standard. An expiratory film is no longer routinely recommended but can accentuate a small apical pneumothorax.
- Review at a bright setting and zoom the apices — small pneumothoraces are lost at normal viewing size.
- ULTRASOUND: high-frequency linear probe, longitudinal across the ribs, anterior chest with the patient supine — this is where gas collects.
- CT is the reference standard and finds occult pneumothoraces a radiograph never shows.
The manoeuvre
- On an erect film, scan the apices and the lateral costophrenic angles for a pleural line.
- On a SUPINE film look for the deep sulcus sign (an abnormally deep, lucent costophrenic angle), a hyperlucent upper abdomen, a sharply outlined hemidiaphragm or cardiac border, and a visible anterior costophrenic recess.
- Confirm no lung markings peripheral to the line, and exclude a skin fold or a companion shadow.
- On ULTRASOUND: absence of LUNG SLIDING, absence of B-lines, and a LUNG POINT — the exact spot where sliding lung meets non-sliding pleura. The lung point is the specific sign; the absence of sliding alone is not.
- Use M-mode: a normal lung gives the seashore sign, a pneumothorax the barcode/stratosphere sign.
- Estimate the size and state the method, and note whether it is under tension.
- Look for the cause: rib fractures, subcutaneous emphysema, bullae, a recent line insertion or biopsy.
What confirms it
- A visceral pleural line with no lung markings beyond it.
- On ultrasound, a LUNG POINT is essentially diagnostic.
What licenses you to exclude it
- Preserved lung sliding at the point examined excludes pneumothorax AT THAT POINT — say where you looked.
- ⚠️ A supine radiograph does not exclude pneumothorax, and this matters most in exactly the patients who get supine films.
- CT is the study that genuinely excludes it.
The classic misread
- Reporting "no pneumothorax" on a supine film.
- Calling a skin fold a pneumothorax — look for lung markings on both sides of the line.
- Missing tension because the report was finished before anyone was told.
- Relying on absent lung sliding alone in a patient with bullae, adhesions, ARDS or main-stem intubation, where sliding is absent without pneumothorax.