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.
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Funding: this study was provided with funding by the R&D budget, Warrington Hospital NHS Trust.
Conflicts of interest: none.