Abstract
The diagnosis of saber-sheath trachea is easy at CT due to its cross-sectional imaging, but the significance of this CT sign has not been evaluated in the diagnosis of chronic obstructive pulmonary disease (COPD). Various signs of COPD were compared between a series of 20 patients with a saber-sheath trachea at CT (tracheal index ≤ 66%) and a group of 20 pneumologic control patients without saber-sheath trachea (tracheal index ≥ 70%). These signs included clinical and standard radiographic indices of COPD, sternum-spine distance and 3 functional tests of COPD: forced expiratory volume in one second, carbon monoxide diffusing lung capacity, and functional residual capacity (FRC). A significant difference was found between the 2 groups, concerning the values of FRC (p<10−4) and of sternum-spine distance (p<10−2). The tracheal index was significantly correlated with the FRC values (r= −0.611; p<10−5) and with the sternum-spine distance (r= −0.322; p<0.05). No other significant difference was observed. It is concluded that saber-sheath trachea is basically a sign of hyperinflation.