I’ve always assumed scanning the chest at the level of the nipples would be best for finding a pneumothorax. Recently, I had a trauma patient where I excluded pneumothorax after a negative ultrasound scan. The CXR was negative as well. But the CT showed a rather big right sided pneumothorax that I hadn’t spotted with US. A recent article in Journal of American Emergency Medicine shows we probably need to scan lower to catch the most pneumos.
What’s the best area to scan for a pneumo? Do you need to scan several, or even all areas of the chest? This was a retrospective convenience sample of CT’s of 183 trauma patients with pneumothorax. The chest was divided into 13 zones shown in the image below. They looked for the zones affected by the pneumothorax and the zone for the largest anterior-posterior diameter.
There was increasing frequency of pneumothoraces from lateral to medial, and from apical to basal aspects of the lungs. The zones most frequently affected by pneumothorax in this study were 9, 11 and 12, the most anterior and basal zones.
Only larger pneumos need treatment and placement of a chest tube. According to this study, larger pneumos will also affect the more apical zones that I usually scan. But for the highest sensitivity, you need to scan the anterior, but most basal lung aspects. Time to change.