26yo male presents post MVA 80kph. No obvious chest injury. Trauma reg states decreased AE R side.
CXR not impressive.
R anterior chest US showing good pleural movement.
The patient underwent pan scan given the mechanism. Pan scan revealed a small apical R sided pneumothorax.
Re-examination with US revealed an area of absent lung sliding superior to the original probe position. However it was quite subtle on the abdo probe: just a small area lying between areas of normal lung sliding.
lung US showing an area of absent lung sliding (pink on still image) indicating a small pneumothorax.
This is much more obvious with the linear probe.
Ultrasound has a much higher sensitivity for detecting pneumothorax than supine CXR in the trauma patient (1).
In a prospective single blind trail of US vs CXR in trauma patient, Blaivas et al showed that US is infinitely more sensitive and specific (2) than CXR and had a good sensitivity and specificity (see below) when compared to the gold standard of chest CT.
However, EPs performing the US were highly skilled in US and received specific training in thoracic US.
More recently Hyacinthe et al (3) showed a less desirable sensitivity profile of lung US against chest CT
Of note almost all of the pneumothoraces which were missed did not require intervention and were discharged after observation. The one missed pneumothorax which got an ICC also had significant sc emphysema (!)
Helland et al (4) recently showed that looking at one vs four lung views did not improve the accuracy of lung US (4). Also in their study, the missed pneumothoraces were small and did not require intervention. For a pneumothorax requiring intervention, the sensitivity and specificity of lung US is very high (see below).
So we need to see lung US in trauma in the same way as abdominal US in trauma: a pneumothorax cannot be excluded on lung US alone. It is most likely to be positive with clinically significant pathology.
1. Blaivas, M., Lyon, M. and Duggal, S. (2005), A Prospective Comparison of Supine Chest Radiography and Bedside Ultrasound for the Diagnosis of Traumatic Pneumothorax. Academic Emergency Medicine, 12: 844–849.
2. Gentry Wilkerson, R. and Stone, M. B. (2010), Sensitivity of Bedside Ultrasound and Supine Anteroposterior Chest Radiographs for the Identification of Pneumothorax After Blunt Trauma. Academic Emergency Medicine, 17: 11–17.
3. Hyacinthe AC, Broux C, Francony G, et al. (2012) Diagnostic accuracy of ultrasonography in the acute assessment of common thoracic lesions after trauma.Chest;141(5):1177–83
4. Helland G, Gaspari R, Licciardo S et al (2016), Comparison of Four Views to Single View Ultrasound Protocols to Identify Clinically Significant Pneumothorax. Academic Emergency Medicine. Epub before print.