RE: Association of Abnormal Pulmonary Vasculature on CT Scan for COVID-19 Infection with Decreased Diffusion Capacity in Follow Up: a retrospective cohort study.

Abstract

\n Background: Coronavirus Disease 2019 (COVID-19) is a highly contagious respiratory viral illness causing pneumonia and systemic disease. Abnormalities in pulmonary function after COVID-19 infection have been described. The determinants of these abnormalities are unclear. We hypothesized that inflammatory biomarkers and CT scan parameters at the time of infection would be associated with abnormal gas exchange at short term follow-up.Methods: We studied subjects who were hospitalized for COVID-19 pneumonia and then discharged. Serum inflammatory biomarkers, CT scan, and clinical characteristics were assessed during the hospitalization. CT images were evaluated by Functional Respiratory Imaging with automated tissue segmentation algorithms of the lungs and pulmonary vasculature. Volumes of the pulmonary vessels that were ≤5mm (BV5), 5-10mm (BV5_10), and ≥10mm (BV10) in cross sectional area were analyzed. Additionally, the amount of opacification on CT (i.e. ground glass opacities) was quantified in each patient. Pulmonary function tests were performed 2-3 months after discharge. We divided subjects into those with a DLCO <80% predicted (Low DLCO) and those with a DLCO ≥80% predicted (Normal DLCO) based on these pulmonary function tests. Results: 38 subjects were included in our analysis. 31 out of 38 (81.6%) subjects had a DLCO<80% predicted. Hemoglobin, inflammatory biomarkers, spirometry and lung volumes were similar between groups. CT opacification and BV5 were not different between groups, but both Low and Normal DLCO groups had lower BV5 measures compared to healthy controls. BV5_10 and BV10 measures were higher in the Low DLCO group compared to the Normal DLCO group. Both BV5_10 and BV10 in the Low DLCO group were greater compared to healthy controls. BV5_10 was independently associated with DLCO<80% in multivariable logistic regression (OR 1.29, 95% CI 1.01, 1.64). BV10 negatively correlated with DLCO% predicted (r=-0.343, p=0.035). Conclusions: Low DLCO is common after COVID-19 infection, and abnormalities in pulmonary vascular volumes at the time of hospitalization are independently associated with a low DLCO. There was no relationship between inflammatory biomarkers during hospitalization and DLCO. These findings suggest that pulmonary vascular abnormalities during hospitalization with COVID-19 might have long-lasting effects on pulmonary function.