Chest X-ray Findings
                        ====================

þ "Ring around Artery Sign"
 - A well-defined lucency around the right pulmonary artery, which
   is a sign of mediastinal emphysema.

Mediastinal Size:
 - Traditional: 8 cm upper limit for mediastinal width

- "The 8 cm upper limit for normal mediastinal width, set in the 1970s
does not apply in the modern trauma room. Changes in the position of the
x ray cassette, and lengthening of the distance between the patient and
the x ray source will significantly reduce magnification. A new range of
upper limits is defined for the radiographical techniques possible in
different trauma settings."

The mediastinum. Is it wide?
C E Gleeson, R L Spedding, L A Harding, M Caplan
Emerg Med J 2001; 18:183-185.