Expiratory pulmonary vascular retention on computed tomography as a marker of asthma severity

Background: While chronic airway inflammation and remodeling are well-established features of severe asthma, the associated vascular changes remain poorly understood. Objective: We assessed severity-related changes in pulmonary vascular remodeling and their associations with clinical features and computed tomography (CT)-based airway functional measures among patients with asthma. Methods: Full inspiratory and normal expiratory CT scans were analyzed from 159 healthy subjects, 53 patients with nonsevere asthma, and 159 patients with severe asthma after 3:1:3 propensity score matching. Total pulmonary blood vessel volume during inspiration and expiration (respectively, TBV_IN and TBV_EX), vascular compressibility between inspiration and expiration (TBV_comp), and expiratory small-vessel fraction were quantified. Associations with clinical variables and CT-derived indexes—air-trapping percentage (AirT%) and parenchymal deformation (Jacobian)—were assessed by multivariable regression. Results: TBV_comp decreased stepwise from healthy subjects to those with nonsevere and severe asthma (P < .05). In multivariable regression analyses with additional adjustment for Jacobian and AirT%, higher TBV_EX was significantly associated with worse lung function (lower percentage predicted forced expiratory volume in 1 second [FEV₁], β = −0.40; lower FEV₁/FVC, β = −0.26) and higher cumulative steroid corticosteroid dose (β = 0.13, all P < .05). Lower TBV_comp remained independently associated with higher blood eosinophil count (β = −0.37, P < .05). Conclusion: TBV_comp decreases with increasing asthma severity and remains independently associated with type 2 inflammation and possibly with clinical burden after accounting for lung mechanics. These findings suggest that CT-based expiratory vascular metrics capture intrinsic vascular alterations beyond mechanical factors and may add value for asthma phenotyping and disease monitoring.