Pulmonary blood volume redistribution in COVID-19 patients of different severity and its predictive value for six-month outcomes in the less pathogenic Omicron variant

Background The redistribution of pulmonary blood volume (PBV) across COVID-19 severity levels and its prognostic value for the less pathogenic, predominantly upper respiratory tract-infecting Omicron variant remain unclear. This study investigates PBV distribution patterns and validates its predictive utility for Omicron outcomes.Methods This retrospective study enrolled consecutive patients (November 2022–January 2023) with baseline CT and clinical data, followed for six months. Patients were divided into mild/moderate (MM) and severe/critical (SC) groups according to COVID-19 severity. Pre-trained deep learning algorithms quantified total, lobar, and vessel-size-specific PBV. Adjusted multivariable analyses determined odds ratios (OR) for clinical outcomes, and logistic regression models based on PBV were constructed to predict adverse events.Results Among 921 patients (61 ± 20 years, 460 men), 755 were in the MM group and 166 in the SC group. Compared to MM patients, SC patients showed significantly lower total PBV (259 mL vs. 239 mL, p = 0.002) and redistribution from lower to upper lobes (upper vs. lower; MM, 21% vs. 23%; SC, 23% vs. 18%) and from small-calibre (≤5 mm2, 44% vs. 32%, p < 0.0005) to large-calibre (>10 mm2, 39% vs. 51%, p < 0.0005) vessels. PBV (especially in vessels ≤5 mm2) predicted six-month composite outcomes (OR = 4.66, AUC = 0.79, sensitivity = 92%) and mortality (OR = 3.34, AUC = 0.75, sensitivity = 93%) for the Omicron variant with high sensitivity, but at a higher risk threshold (42%) than that reported for more pathogenic variants in previous publications.Conclusions Severe/critical COVID-19 is associated with reduced PBV and its redistribution across lung regions and vessel sizes. PBV retains predictive value for clinical outcomes in the immune-evasive Omicron variant.