UMEM Educational Pearls

Title: Find the inconsistencies (UPDATED). Written by Dr. Michael Allison

Category: Trauma

Keywords: blunt trauma, pneumothorax, CXR supine, ultrasound, seashore, stratasphere (PubMed Search)

Posted: 2/14/2011 by Haney Mallemat, MD (Updated: 8/28/2014)
Click here to contact Haney Mallemat, MD

Question

(Please note the prior version of this pearl was incorrect with respect to the images referenced. This version is corrected.)

Patient s/p blunt chest trauma. CXR (image 1) vs. lung ultrasound (image 2), do you see any inconsistencies?

Answer

Lung ultrasound in traumatic pneumothorax: The "Stratosphere Sign"

Written by Dr. Michael Allison.

Small to moderate sized pneumothorax (PTX) can be missed on supine CXR.
In normal lung (i.e., no PTX), the visceral and parietal pleura “slides” against each other, creating an ultrasound artifact known as the “seashore sign” (image 4).
Loss of this artifact is called the “stratosphere sign” (image 2) and is sensitive and specific for occult PTX. Please note image 3, the CT for the patient who initially appeared to have a normal CXR (image 1)
A prospective study compared ultrasound vs. supine CXR for detecting PTX; sensitivity was 98% vs. 75% respectively with chest CT being the gold standard for comparison.
Adding lung ultrasound to the FAST exam is known as an E-FAST or “Extended” FAST exam.

For advanced sonographers:

Specificity for PTX increases to 94% when an A-line twice the distance from skin to the pleural line is detected, in the absence of lung-sliding or comet tails.

References

1. Blaivas, M. et al. A prospective comparison of supine chest radiography and bedside ultrasound for the diagnosis of traumatic pneumothorax. Academic Emergency Med. 2005 Sep;12(9):844-9.

2. Lichtenstein D et al. Ultrasound diagnosis of occult pneumothorax. Crit Care Med. 2005 June;33(6): 1231-8.