Four-dimensional computed tomography in expiratory central airway collapse: Disrupting diagnostic paradigms

Expiratory central airway collapse (ECAC) is an under-recognized condition, currently diagnosed by the gold standard dynamic bronchoscopy. Several expiratory chest CT protocols have been used for the initial workup of ECAC with variable accuracy. We compared three expiratory chest CT protocols to determine which one holds the closest correlation with dynamic bronchoscopy to detect ECAC.

We performed a retrospective study of patients who underwent either static end expiratory (SEE), static forced expiratory (SFE), or four-dimensional forced expiratory (4D-FE) CT for the evaluation of ECAC and a confirmatory dynamic bronchoscopy. Chest CT collapsibility index was calculated and compared to the percentage of collapsibility observed during dynamic bronchoscopy using Cohen's Kappa coefficient and diagnostic accuracy assessment.

A total of 96 patients were reviewed (median age: 64 years; median BMI: 32.1 kg/m²; 71 % female). Kappa's coefficient of agreement was 0.735 (substantial agreement) for the 4D-FE protocol, 0.248 (fair agreement) for the SFE protocol, and 0.187 (slight agreement) for the SEE protocol, with dynamic bronchoscopy. The 4D-FE protocol presented the highest sensitivity for detecting ECAC (92.5 %) and identifying severe disease (65.6 %), and the lowest median radiation exposure (530.0 mGy-cm) among the three imaging protocols.

The 4D-FE protocol showed the highest correlation with the gold standard dynamic bronchoscopy for the diagnosis of ECAC and required less radiation exposure than the static expiratory CT protocols.