Clinical features and respiratory pathophysiology of COVID-19 patients ventilated in the prone position: a cohort study

Background: There are few studies that have investigated the response to the prone position in mechanically ventilated COVID-19 patients with acute respiratory distress syndrome (ARDS). We describe the characteristics and outcomes of those patients in a tertiary hospital in Spain. Methods: This is an observational study in consecutive, mechanically ventilated COVID-19 patients. The primary endpoint was to describe the respiratory pathophysiology and clinical outcomes of COVID-19 patients treated by mechanical ventilation in the prone position. Results: Of 84 patients mechanically ventilated in the prone position, 19 (22%) were successfully extubated and 43 (51%) were discharged from the ICU. The duration of mechanical ventilation and ICU length of stay were 11 days (IQR 8-16) and 15 days (IQR 9-25), respectively. On admission to ICU, 61% patients had a moderate ARDS according to the Berlin criteria. 76% had 4 lung quadrants affected. After intubation, the median PaO2/FiO(2) was 105 (IQR 76-138), ventilatory ratio was 1.48 (IQR 1.16-1.88), and compliance was 33 mL cm H2O-1 (IQR 25-4] ).The median number of cycles in the prone position was 2 (1-3), with a median of total hours in the prone position of 76 (IQR 64-111). 72 h after the first prone position cycle the median PaO2/FiO(2) increase was up to 193 (IQR 152-251), but the compliance was similar to the basal level (34 mL cm H2O-1 [IQR 26-43]). However, the percentage of patients with normal compliance (> 50 mL cm H2O-1) increased with the prone position from 15% (n = 13) to 32% (n = 27) after 72 h. Conclusions: In our study, the COVID-19 patients with respiratory failure presented respiratory mechanics, gas exchange parameters, and a response to prone ventilation similar to those observed in other causes of ARDS.