Failing categorization of severe COVID-19 ARDS into ventilatory subphenotypes studied via the clinical-histopathologic relationship

Background: Categorization of severe COVID-19 related acute respiratory distress syndrome (CARDS) into subphenotypes does not consider the trajectories of respiratory mechanoelastic features and histopathologic patterns. This study aimed to assess the correlation between mechanoelastic ventilatory features and lung histopathologic findings in critically ill patients who died because of CARDS. Methods: Mechanically ventilated patients with severe CARDS who had daily ventilatory data were considered. The histopathologic assessment was performed through full autopsy of deceased patients. Patients were categorized into two groups according to the median worst respiratory system compliance during ICU stay (Crs(ICU)). Results: Eighty-seven patients admitted to ICU had daily ventilatory data. Fifty-one (58.6%) died in ICU, 41 (80.4%) underwent full autopsy and were considered for the clinical-histopathological correlation analysis. Respiratory system compliance at ICU admission and its trajectory were not different in survivors and nonsurvivors. Median Crs(ICU) in the deceased patients was 22.9 ml/cmH(2)O. An inverse correlation was found between the Crs(ICU) and late-proliferative diffuse alveolar damage (DAD) (r = -0.381, p = 0.026). Late proliferative DAD was more extensive (p = 0.042), and the probability of stay in ICU was higher (p = 0.004) in the "low" compared to the "high" Crs(ICU) group. Cluster analysis further endorsed these findings. Conclusions: In critically ill mechanically ventilated patients, worsening of the respiratory system compliance correlated pathologically with the transition from early damage to late fibroproliferative patterns in nonsurvivors of CARDS. Categorization of CARDS into ventilatory subphenotypes by mechanoelastic properties at ICU admission does not account for the complexity of the histopathologic features.