Quantitative Computed Tomography Measurement of Tracheal Cross-Sectional Areas in Relapsing Polychondritis: Correlations with Spirometric Values

Abstract

Background: Although tracheal stenosis occurs in relapsing polychondritis (RP), no studies exist that have clarified correlations between quantitative airway measurement and spirometry in RP patients. Objectives: The aim of this study was to investigate correlations between the cross-sectional area (CSA) of the trachea and spirometric values in patients with RP. Methods: The institutional review board approved this retrospective study, and written informed consent was waived. Twenty-six patients with RP underwent spirometry and chest computed tomography (CT) at full inspiration and end-expiration. On inspiratory and expiratory chest CT images, CSA at the intrathoracic trachea was measured for all CT slices, and the mean and minimum tracheal CSA were obtained. Correlations between the tracheal CSA and spirometric values were assessed by Spearman's rank correlation analysis. Results: Tracheal CSA measurements for inspiratory and expiratory scans were significantly correlated with FEV₁, FEV_25-75%, and peak flow values (ρ = 0.51-0.86, p < 0.01). During each inspiratory or expiratory phase, the minimum tracheal CSA achieved a higher correlation coefficient with spirometric values than the mean CSA. Conclusion: Tracheal dimensions for both inspiratory and expiratory CT are significant predictors of pulmonary function in patients with RP. The narrowest tracheal dimension likely determines the severity of airflow limitation in RP.