ABSTRACT
Background: It has been suggested that COVID-19-associated severe respiratory failure (CARDS) might differ from usual acute respiratory distress syndrome (ARDS) due to failing auto-regulation of pulmonary vessels and higher shunt. We sought to investigate pulmonary hemodynamics and ventilation properties in patients with CARDS compared to patients with ARDS of pulmonary origin. Methods: Retrospective analysis of prospectively collected data of consecutive adults with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 patients treated on our ICU in 04/2020 and comparison of the data to matched controls with ARDS due to respiratory infections treated on our ICU from 01/2014 to 08/2019 and for whom pulmonary artery catheter data were available. Results: CARDS patients (n = 10) had similar ventilation characteristics as compared to ARDS (n = 10) patients. Still, mechanical power applied by ventilation was significantly higher in CARDS patients (23.4 ± 8.9 J/min) than in ARDS (15.9 ± 4.3 J/min; p<0.05). COVID-19 patients had similar pulmonary artery pressure but significantly lower pulmonary vascular resistance, as cardiac output was higher in CARDS vs. ARDS patients (p<0.05). Shunt fraction and dead space were similar in CARDS compared to ARDS (p>0.05) and was in both groups correlated with hypoxemia. The arterio-venous pCO2 difference (DpCO2) was elevated (CARDS 5.5±2.8 mmHg vs. ARDS 4.7±1.1 mmHg; p>0.05) as was P(v-a)CO2/C(a-v)O2 ratio (CARDS mean 2.2±1.5 vs. ARDS 1.7±0.8; p>0.05). Conclusions: Respiratory failure in COVID-19 patients seems to differ only slightly from ARDS regarding ventilation characteristics and pulmonary hemodynamics. Differences are mainly due to increased CO2 production in CARDS patients. Our data indicate microcirculatory dysfunction. More data needs to be collected to assure these findings and gain more pathophysiological insights in COVID-19 and respiratory failure.