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Prone Positioning Unloads the Right Ventricle in Severe ARDS^*

^* From the Medical Intensive Care Unit, University Hospital Ambroise Paré, Assistance Publique Hôpitaux de Paris, Boulogne, France.

Correspondence to: François Jardin, MD, Hôpital Ambroise Paré, 9 Avenue Charles de Gaulle, 92104, Boulogne Cedex, France; e-mail: francois.jardin{at}apr.ap-hop-paris.fr

Abstract

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 18 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 18 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 18 h of PP (p = 0.000).

Conclusion: In the most severe forms of ARDS, PP was an efficient means of controlling RV pressure overload.

Key Words: acute cor pulmonale • ARDS • echocardiography • prone position • right ventricle