Is Computed Tomography Airway Count Related to Asthma Severity and Airway Structure and Function?

Document Type


Publication Date



American Journal of Respiratory and Critical Care Medicine





First Page


Last Page


URL with Digital Object Identifier



Rationale: In patients with asthma, x-ray computed tomography (CT) has provided evidence of thickened airway walls and airway occlusions, but the total number of CT-visible airways and its relationship with disease severity is unknown.

Objectives: To measure CT total-airway-count (TAC) in asthma and evaluate relationships with asthma severity, airway morphology, pulmonary function and magnetic-resonance-imaging (MRI) ventilation.

Methods: Participants underwent post-bronchodilator inspiratory CT, and pre- and post-bronchodilator spirometry and hyperpolarized 3He MRI. CT TAC was quantified as the sum of airways in the segmented airway-tree, and airway wall-area-percent (WA%) and lumen-area (LA) were measured. MRI ventilation abnormalities were quantified as the ventilation-defect-percent (VDP). Measurements and Main

Results: We evaluated 70 participants including 15 Global-Initiative-for-Asthma (GINA) steps 1-3, 19 GINA4 and 36 GINA5 asthmatics. As compared with GINA1-3, TAC was significantly diminished in GINA4 (p=0.03) and GINA5 (p=0.045). Terminal airway intraluminal occlusion was present in five (two GINA4, three GINA5) of 70 participants. Sub-subsegmental airways were CT-invisible or missing in 69/70 participants; the most common number of missing sub-subsegments was 10. Participants with ≥10 missing subsegments had worse WA% (p<0.0001), LA (p<0.0001) and VDP (p=0.03) than those with <10 missing subsegments. In a multivariable-model, TAC (β=0.50, p=0.001) independently predicted FEV1 (R2=0.27, p=0.003) and in a separate model, TAC (β=-0.53, p<0.0001) independently predicted airway WA% (R2=0.32, p=0.0001).

Conclusions: TAC was significantly diminished in participants with greater asthma severity and was related to airway wall thickness and ventilation-defects. Fewer airways in severe as compared with mild asthma challenges our understanding of airways-disease in asthma.


This is an author-accepted manuscript of an article initially published by the American Thoracic Society. Final published version is available at: https://doi.org/10.1164/rccm.201908-1552OC

This document is currently not available here.

Find in your library