Intrathoracic tracheal dimensions and shape changes in chronic obstructive pulmonary disease.

Changes in intrathoracic tracheal dimensions and shape in patients with chronic obstructive pulmonary disease (COPD) are commonly noted, but the cause is not clear. This study reveals a significantly larger lateral tracheal diameter (LTD) in patients with COPD. The larger LTD has a significant positive linear correlation with a larger lateral chest diameter. This finding supports the hypothesis that in patients with COPD the increase in volume of both lungs pressing on the mediastinum will exert a lateral pressure on the trachea, resulting in a decrease in frontal and an increase in the lateral trachea diameter. Patients with COPD have a smaller tracheal index: FTD/LTD (FTD: frontal tracheal diameter). Saber-sheath trachea (tracheal index < 2/3) is a specific radiographic diagnostic parameter for the diagnosis of COPD (specificity, 92.9%), although the sensitivity (39.1%) is low.