Effects of Extravascular Lung Water on Prone Position Efficacy in Patients With ARDS

The study will investigate the influence that extravascular lung water index (EVLWi) could have on the efficacy and persistance of efficacy of prone position in patients with acute respiratory distress syndrome. Prone position will increase blood oxygenation in 75% of the cases and will be persistant in half of the cases. Unfortunately, no clinical criteria has been found correlated with efficacy. The quantity of lung edema, with increased lung weight, could be a determinant factor of efficacy and the persistance of the efficacy. EVLWi, assessed with the PiCCO2 device, reflects the quantity of fluid accumulated in interstitial and alveolar spaces. The hypothesis is that patients with higher EVLWi will have less efficacy of prone position in oxygenation and also that the beneficial effects of prone position will last shorter compared to patients with lower EVLWi.