title: The mediastinum--is it wide?
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Accident and Emergency, Warrington Hospital NHS Trust.
authors.forename: C E
authors.initials: CE
authors.lastname: Gleeson
authors.forename: R L
authors.initials: RL
authors.lastname: Spedding
authors.forename: L A
authors.initials: LA
authors.lastname: Harding
authors.forename: M
authors.initials: M
authors.lastname: Caplan
mesh_terms: D006801:Humans; D008482:Mediastinum / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D016683:Supine Position / Q000502:physiology; D014057:Tomography, X-Ray Computed; D014947:Wounds and Injuries / Q000000981:diagnostic imaging*