Haemodynamic changes during prone versus supine position in patients with COVID-19 acute respiratory distress syndrome

BACKGROUND: Prone positioning improves oxygenation in patients with acute respiratory distress syndrome (ARDS) secondary to COVID-19. However, its haemodynamic effects are poorly understood. OBJECTIVES: The objective of this study was to investigate the acute haemodynamic changes associated with prone position in mechanically ventilated patients with COVID-19 ARDS. The primary objective was to describe changes in cardiac index with prone position. The secondary objectives were to describe changes in mean arterial pressure, FiO(2), PaO(2)/FiO(2) ratio, and oxygen delivery (DO(2)) with prone position. METHODS: We performed this cohort-embedded study in an Australian intensive care unit, between September and November 2021. We included adult patients with severe COVID-19 ARDS, requiring mechanical ventilation and prone positioning for respiratory failure. We placed patients in the prone position for 16 h per session. Using pulse contour technology, we collected haemodynamic data every 5 min for 2 h in the supine position and for 2 h in the prone position consecutively. RESULTS: We studied 18 patients. Cardiac index, stroke volume index, and mean arterial pressure increased significantly in the prone position compared to supine position. The mean cardiac index was higher in the prone group than in the supine group by 0.44 L/min/m2 (95% confidence interval, 0.24 to 0.63) (P < 0.001). FiO(2) requirement decreased significantly in the prone position (P < 0.001), with a significant increase in PaO(2)/FiO(2) ratio (P < 0.001). DO(2) also increased significantly in the prone position, from a median DO(2) of 597 mls O(2)/min (interquartile range, 504 to 931) in the supine position to 743 mls O(2)/min (interquartile range, 604 to 1075) in the prone position (P < 0.001). CONCLUSION: Prone position increased the cardiac index, mean arterial pressure, and DO(2) in invasively ventilated patients with COVID-19 ARDS. These changes may contribute to improved tissue oxygenation and improved outcomes observed in trials of prone positioning.