A quantitative analysis of extension and distribution of lung injury in COVID-19 : a prospective study based on chest computed tomography

BackgroundTypical features differentiate COVID-19-associated lung injury from acute respiratory distress syndrome. The clinical role of chest computed tomography (CT) in describing the progression of COVID-19-associated lung injury remains to be clarified. We investigated in COVID-19 patients the regional distribution of lung injury and the influence of clinical and laboratory features on its progression.MethodsThis was a prospective study. For each CT, twenty images, evenly spaced along the cranio-caudal axis, were selected. For regional analysis, each CT image was divided into three concentric subpleural regions of interest and four quadrants. Hyper-, normally, hypo- and non-inflated lung compartments were defined. Nonparametric tests were used for hypothesis testing (alpha =0.05). Spearman correlation test was used to detect correlations between lung compartments and clinical features.ResultsTwenty-three out of 111 recruited patients were eligible for further analysis. Five hundred-sixty CT images were analyzed. Lung injury, composed by hypo- and non-inflated areas, was significantly more represented in subpleural than in core lung regions. A secondary, centripetal spread of lung injury was associated with exposure to mechanical ventilation (p<0.04), longer spontaneous breathing (more than 14 days, p<0.05) and non-protective tidal volume (p<0.04). Positive fluid balance (p<0.01), high plasma D-dimers (p<0.01) and ferritin (p<0.04) were associated with increased lung injury.ConclusionsIn a cohort of COVID-19 patients with severe respiratory failure, a predominant subpleural distribution of lung injury is observed. Prolonged spontaneous breathing and high tidal volumes, both causes of patient self-induced lung injury, are associated to an extensive involvement of more central regions. Positive fluid balance, inflammation and thrombosis are associated with lung injury.Trial registration Study registered a priori the 20th of March, 2020. Clinical Trials ID NCT04316884