Prone positioning unloads the right ventricle in severe ARDS

Background: Despite airway pressure limitation, acute cor pulmonale persists in a minority of ARDS patients. Insufficient airway pressure limitation, hypercapnia, or both may be responsible. Because prone positioning (PP) has been shown to be a safe way to reduce airway pressure and to improve alveolar ventilation, we decided to assess its effect on right ventricular (RV) pressure overload in ARDS patients. Methods: Between January 1998 and December 2006, we studied 42 ARDS patients treated by PP to correct severe oxygenation impairment (PaO2/fraction of inspired oxygen ratio, < 100 mm Hg). RV function was evaluated by bedside transesophageal echocardiography, before and after IS h of prone-position ventilation. RV enlargement was measured by RV/left ventricular (LV) end-diastolic area ratio in the long axis. Septal dyskinesia was quantified by measuring short-axis systolic eccentricity of the LV. Results: Before PP, 21 patients (50%) had acute cor pulmonale, defined by RV enlargement associated with septal dyskinesia (group 1), whereas 21 patients had a normal RV (group 2). PP was accompanied by a significant decrease in airway pressure and PaCO2. In group 1, this produced a significant decrease in mean (+/- SD) RV enlargement (from 0.91 +/- 0.22 to 0.61 +/- 0.21) after IS h of PP (p = 0.000) and a significant reduction in mean septal dyskinesia (from 1.5 +/- 0.2 to 1.1 +/- 0.1) after IS h of PP (p = 0.000). Conclusion: In the most severe forms of ARDS, PP was an efficient means of controlling RV pressure overload.