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

Abstract

While chronic airway inflammation and remodeling are well-established features of severe asthma, the associated vascular changes remain poorly understood. 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. 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. 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). 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.