Pulmonary Hemodynamics and Ventilation in Patients With COVID-19-Related Respiratory Failure and ARDS

It has been suggested that COVID-19-associated severe respiratory failure (CARDS) might differ from usual acute respiratory distress syndrome (ARDS) due to failing autoregulation 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.

This was a retrospective analysis of prospectively collected data from consecutive adults with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 patients treated in our ICU in 04/2020 and a comparison of the data to matched controls with ARDS due to respiratory infections treated in our ICU from 01/2014 to 08/2019 for whom pulmonary artery catheter data were available.

CARDS patients (n = 10) had ventilation characteristics similar to those of ARDS (n = 10) patients. Nevertheless, 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 were correlated with hypoxemia in both groups. The arteriovenous pCO₂ difference (▵pCO₂) was elevated (CARDS 5.5 ± 2.8 mmHg vs. ARDS 4.7 ± 1.1 mmHg; P > 0.05), as was the P_(v-a)CO₂/C_(a-v)O₂ ratio (CARDS mean 2.2 ± 1.5 vs. ARDS 1.7 ± 0.8; P > 0.05).

Respiratory failure in COVID-19 patients seems to differ only slightly from ARDS regarding ventilation characteristics and pulmonary hemodynamics. Our data indicate microcirculatory dysfunction. More data need to be collected to assure these findings and gain more pathophysiological insights into COVID-19 and respiratory failure.