COVID-19 versus Non-COVID ARDS: Comparison of Demographics, Physiologic Parameters, Inflammatory Biomarkers and Clinical Outcomes.

RATIONALE: There is an urgent need for improved understanding of the mechanisms and clinical characteristics of acute respiratory distress syndrome (ARDS) due to COVID-19. OBJECTIVES: To compare key demographic and physiologic parameters, biomarkers and clinical outcomes of COVID-19 ARDS and ARDS secondary to direct lung injury from other etiologies of pneumonia. METHODS: We enrolled 27 patients with COVID-19 ARDS in a prospective, observational cohort study, and compared them with a historical, pre-COVID-19 cohort of patients with viral ARDS (n=14), bacterial ARDS (n=21), and ARDS due to culture-negative pneumonia (n=30). We recorded clinical demographics, measured respiratory mechanical parameters, collected serial peripheral blood specimens for measurement of plasma interleukin-(IL)-6, IL-8, and IL-10, and followed patients prospectively for patient-centered outcomes. We conducted between group comparisons with non-parametric tests and analyzed time-to-event outcomes with Kaplan-Meier and Cox proportional hazards models. RESULTS: Patients with COVID-19 ARDS had higher body mass index and were more likely to be Black, or residents of skilled nursing facilities, compared to non-COVID-19 ARDS (p<0.05). COVID-19 patients had lower delivered minute ventilation compared to bacterial and culture-negative ARDS (post-hoc p<0.01), but not compared to viral ARDS. We found no differences in static compliance, hypoxemic indices or carbon dioxide clearance between groups. COVID-19 patients had lower IL-6 levels compared to bacterial and culture-negative ARDS at early time points post-intubation, but no differences in IL-6 levels compared to viral ARDS. COVID-19 patients had longer duration of mechanical ventilation but similar 60-day mortality, both in unadjusted and adjusted analyses. CONCLUSIONS: COVID-19 ARDS bears several similarities to viral ARDS but demonstrates lower minute ventilation and lower systemic levels of IL-6 compared to bacterial and culture-negative ARDS. COVID-19 ARDS was associated with longer dependence on mechanical ventilation compared to non-COVID ARDS. Such detectable differences of COVID-19 do not merit deviation from evidence-based management of ARDS but suggest priorities for clinical research to better characterize and treat this new clinical entity.