Glottis Closure Influences Tracheal Size Changes in Inspiratory and Expiratory CT in Patients with COPD

Rationale and Objectives: The opened or closed status of the glottis might influence tracheal size changes in inspiratory and expiratory computed tomography (CT) scans. We investigated if the glottis status makes the tracheal collapse differently correlate with lung volume difference between inspiratory and expiratory CT scans. Materials and Methods: Forty patients with chronic obstructive pulmonary disease whose glottis was included in the acquired scanned volume for lung CT were divided into two groups: 16 patients with the glottis closed in both inspiratory and expiratory CT, and 24 patients with the glottis open in at least one CT acquisition. Lung inspiratory (Vinsp) and expiratory (Vexp) volumes were automatically computed and lung \u3b4V was calculated using the following formula: (Vinsp - Vexp)/Vinsp 7 100. Two radiologists manually measured the anteroposterior diameter and cross-sectional area of the trachea 1 cm above the aortic arch and 1 cm above the carina. Tracheal collapse was then calculated and correlated with lung \u3b4V. Results: In the 40 patients, the correlations between tracheal \u3b4anteroposterior diameter and \u3b4cross-sectional area at each level and lung \u3b4V ranged between 0.68 and 0.74 (\u3c1) at Spearman rank correlation test. However, in the closed glottis group, the correlations were higher for all measures at the two levels (\u3c1 range: 0.84-0.90), whereas in the open glottis group, correlations were low and not statistically significant (\u3c1 range: 0.29-0.34) at the upper level, and moderate at the lower level (\u3c1 range: 0.51-0.55). Conclusions: A closed or open glottis influences the tracheal size change in inspiratory and expiratory CT scans. With closed glottis, the tracheal collapse shows a stronger correlation with the lung volume difference between inspiratory and expiratory CT scans