A20-06 Reduced Expiratory Pulmonary Vascular Adaptation Across Asthma Severity Assessed by Quantitative CT

Abstract Rationale Beyond airway remodeling, asthma may also involve reduced pulmonary vascular distensibility, limiting normal respiratory-phase modulation and resulting in residual vascular volume during expiration. However, these dynamics have not been comprehensively characterized across severity. We used quantitative CT (qCT) of paired inspiratory and expiratory scans to measure vascular volume changes and examined their relationships with lung function, inflammatory biomarkers, and functional CT-based variables. Methods We analyzed paired inspiratory-expiratory CT scans from 371 participants, harmonized using 1:3:3 propensity score matching for age, sex, height, weight, BMI, and smoking status across healthy, non-severe, and severe asthma groups. Quantitative CT was used to derive vascular volumes at inspiration and expiration (TBVIN, TBVEX), the percent volume change between phases, and the fraction of small vessels (BV5EX/TBVEX). Functional lung metrics included Jacobian, ADI, AirT%, and Emph%. Spirometry and biomarkers of type 2 inflammation (blood eosinophil count, FeNO, total IgE) were obtained clinically. Associations were evaluated using Spearman correlations and multivariable regression models adjusted for age, sex, height, weight, BMI, and smoking history, with additional stratified analyses comparing non-severe and severe asthma. Results TBV reduction (%) declined stepwise from healthy to non-severe and severe asthma, indicating reduced expiratory vascular volume change with increasing severity (p 0.05). BV5EX/TBVEX was higher in asthma and strongly associated with airflow limitation (FEV1 % predicted, ρ = −0.58), whereas greater TBV reduction (%) related to better ventilatory mechanics (FEV1/FVC, ρ = +0.46). Both indices also correlated with CT markers of hyperinflation and ventilation heterogeneity (AirT%, Emph% and fSAD%). Severity-stratified regression showed stronger coupling between impaired vascular emptying and parenchymal deformation in severe asthma, including TBVEX vs ADI (βsevere = −0.49 vs βnon-severe = −0.07) and TBV reduction (%) vs Jacobian (βsevere = +0.44 vs + 0.10), with significant interactions (p 0.05). TBVEX showed a modest positive association with FeNO, while TBV reduction (%) was weakly but significantly inversely related to total IgE (p 0.05), suggesting that inflammatory activity may contribute in part to reduced vascular compliance. Conclusions A progressive decrease in TBV reduction (%) with increasing asthma severity indicates impaired expiratory vascular emptying. This reduced vascular adaptability was related to airflow limitation, regional mechanical heterogeneity, and modest type 2 inflammatory activity. Quantitative CT assessment of respiratory-phase vascular dynamics may provide complementary information for asthma phenotyping and monitoring. This abstract is funded by: This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. RS-2023-NR077008, NRF-2023R1A2C2003781).