Gas-exchange deficit and systemic hypoperfusion in COVID-19 and non-COVID-19 young adult patients with pneumonia

Background: Lung damage leading to gas-exchange deficit and sepsis leading to systemic hypoperfusion are well-known features of severe pneumonia. Although frequently described in COVID-19, their prognostic impact in COVID-19-related pneumonia vs COVID-19-urelated pneumonia has never been compared. This study assesses fundamental gas-exchange and hemodynamic parameters and explores their prognostic impact in COVID-19 pneumonia and non-COVID-19 pneumonia. Methods: We prospectively evaluated arterial pO2/FiO2, alveolar to arterial O2 gradient, shock index, and serum lactate in 126 COVID-19 pneumonia patients, aged 18- 65, presenting to the emergency department with acute, non-hypercapnic respiratory failure. As a control group we identified 1:1 age-, sex-, and pO2/FiO2-matched COVID-19-urelated pneumonia patients. Univariate and multivariable predictors of 30-day survival were identified in both groups. Results: COVID-19 patients showed lower arterial serum lactate concentration (p<0.001) and shock index (p<0.001) values as compared to non-COVID-19 patients. While we did not observe differences in lactate concentration or in shock index values in deceased vs surviving COVID-19 patients (respectively, p=0.7 and p=0.6), non-COVID-19 deceased patients showed significantly higher lactate and shock index than non-COVID-19 survivors (p<0.001 and p=0.03). The pO2/FiO2 was the most powerful determinant of survival by Cox regression multivariate analysis in COVID-19 patients (p=0.006), while it was lactate in non-COVID-19 patients (p=0.001). Conclusions: As compared to COVID19-unrelated pneumonia, COVID-19 pneumonia outcome seems more strictly correlated to the extent of lung damage, rather than to the systemic circulatory and metabolic derangements typical of sepsis.