An occult pneumothorax is seen on CT but was not identified previously on chest radiography, comprising as many as 50% of all pneumothoraces, with an overall incidence of 5% in patients with trauma. In many cases, this type of pneumothorax is managed conservatively with serial imaging and resolves over time, without requiring the placement of a chest tube. However, decompression should be considered if the patient is symptomatic, hemodynamically unstable, or has a pneumothorax greater than 10% in size. Another indication for decompression, although controversial, is the delivery of positive pressure ventilation. Whether these patients should have a chest tube or pigtail placed preemptively is up for debate; for now, the decision should be made on a case-by-case basis.

References

• Ball CG, Kirkpatrick AW, Feliciano DV. The occult pneumothorax: what have we learned? Can J Surg. 2009;52:E173-E179.
• Ouellet JF, Trottier V, Kmet L, et al. The OPTICC trial: a multi-institutional study of occult pneumothoraces in critical care. Am J Surg. 2009;197:581-586.