CT-derived measurements of pulmonary blood volume in small vessels and need for oxygen in COVID-19 patients

In contrast to early reports of conventional acute respiratory distress syndrome (ARDS) as the underlying pathophysiology of hypoxemic respiratory failure observed in patients with severe COVID-19, more recent findings implicate direct involvement of the pulmonary vasculature in giving rise to these symptoms. In earlier research, we demonstrated that patients with COVID-19 showed markedly reduced pulmonary blood volumes in pulmonary vessels <5 mm2 in cross-sectional area visible on imaging (termed "BV5"), with attendant dilation of larger, more proximal vessels. Here, we present preliminary results in which reduced BV5 is shown to correlate significantly with increased need for supplemental oxygen and abnormal arterial blood gas measurements in hospitalized COVID-19 patients. We suggest a potential mechanistic link between observed clinical, pathological, and imaging findings, and outline how these may be helpful in clinical assessment as well as the development of novel therapies.

Assessment of small pulmonary blood vessels in COVID-19 patients using HRCT

BackgroundMounting evidence supports the role of pulmonary hemodynamic alternations in the pathogenesis of COVID-19. Previous studies have demonstrated that changes in pulmonary blood volumes measured on CT are associated with histopathological markers of pulmonary vascular pruning, suggesting that quantitative HRCT analysis may eventually be useful in the assessment pulmonary vascular dysfunction more broadly. MethodsBuilding upon previous work, automated HRCT measures of small blood vessel volume and pulmonary vascular density were developed. Scans from 103 COVID-19 patients and 108 healthy volunteers were analyzed and their results compared, with comparisons made both on lobar and global levels. ResultsCompared to healthy volunteers, COVID-19 patients showed significant reduction in BV5 (pulmonary blood volume contained in blood vessels of <5 mm2) expressed as BV5/(Total pulmonary blood volume) (p<0.0001), and significant increases in BV5_10 and BV 10 (pulmonary blood volumes contained in vessels between 5 and 10 mm2 and above 10 mm2, respectively) (p<0.0001). These changes were consistent across lobes. ConclusionsCOVID-19 patients display striking anomalies in the distribution of blood volume within the pulmonary vascular tree, consistent with increased pulmonary vasculature resistance in the pulmonary vessels below the resolution of HRCT.