The mediastinum--is it wide?

OBJECTIVE To determine if the 8 cm upper limit for mediastinal width applies in the trauma setting of today. To define the upper limit of normal mediastinal width for supine chest films. METHODS A retrospective review of chest computed tomography scans was conducted to determine the width and position of the mediastinum within the supine chest. Radiographs were performed using a model that enabled the degree of mediastinal magnification to be ascertained in a variety of clinical settings. RESULTS The mean mediastinal width is 6.31 cm. With standard radiographical techniques this mediastinum is magnified to 8.93-10.07 cm. With minor adaptations in radiographical technique this can be reduced to 7.31-7.92 cm. CONCLUSION 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.