Physiological effects and safety of bed verticalization in patients with acute respiratory distress syndrome

AbstractBackground Patient position, such as prone position, can improve prognosis in acute respiratory distress syndrome. Total verticalization is now possible using dedicated beds, but the feasibility, safety, and pulmonary or hemodynamic effects of the position remain unknown in patients with acute respiratory distress syndrome. Methods Adult patients with moderate to severe acute respiratory distress syndrome were prospectively enrolled in this single-center pilot study. After protocolized hemodynamic optimization, they were gradually verticalized using a dedicated bed, from a 30° semi-seated position (baseline) to different levels of inclination (0°, 30°, 60°, and 90°), before returning to the baseline position. The duration of each level was 30 minutes, at the end of which ventilatory (including respiratory mechanics, transpulmonary pressures, end-expiratory lung volumes, mechanical power, and gas exchange parameters) and hemodynamic (including cardiac output and stroke volume by transpulmonary thermodilution, mean arterial pressure, sand serum lactate levels) variables, along with potential adverse events, were recorded. The primary endpoint was the variation in transpulmonary driving pressure through the verticalization procedure. Results From May 2020 through January 2021, 30 patients were included. Transpulmonary driving pressure increased slightly from baseline (median and interquartile range [IQR], 9 [5–11] cmH2O) to the 90° position (10 [7–14] cmH2O; P < 10−2 for the overall effect of position in mixed model). Although static compliance of the respiratory system decreased with verticalization, lung compliance remained stable. End-expiratory lung volume increased with verticalization, in parallel to decreases in alveolar strain and mechanical power and increased arterial oxygenation. Although mean arterial pressure remained stable, verticalization was associated with decreased cardiac output and stroke volume, and increased norepinephrine doses and serum lactate levels, prompting interruption of the procedure in two patients. There were no adverse events such as falls or equipment accidental removals. Conclusions In patients with acute respiratory distress syndrome, bed verticalization at the 90° position may have potential respiratory benefits, but at the cost of hemodynamic impact, which deserves caution and further research. Trial registration ClinicalTrials.gov registration number NCT04371016, April 24, 2020