Which findings on chest radiography suggest pneumomediastinum (PM)?

Updated: Feb 26, 2019
  • Author: Patrick L Carolan, MD; Chief Editor: Girish D Sharma, MD, FCCP, FAAP  more...
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Radiolucent streaks representing free air may be observed tracking along the margins of the heart, within the retrosternal space, or surrounding the trachea. Typical features of pneumomediastinum seen on chest radiography are caused by air outlining normal anatomic structures as it tracks from the mediastinum producing the thymic sail sign, "ring around the artery" sign, tubular artery sign, double bronchial wall sign, continuous diaphragm sign, and the extrapleural sign (see the image below, which is a chest radiograph demonstrating pneumomediastinum as well as subcutaneous emphysema in a female with asthma intubated for respiratory failure).

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