In this interventional study we want to evaluate the effect of Variable ventilation (1) in patients with ARDS. Patients will be mechanically ventilated with Variable Ventilation (3 step with increased level of variability) and traditional CMV, for a total of 4 step. Each step lasts in 60 minutes. During this period we will record the gas exchange parameters and the mechanics of the respiratory system.~1. Arold S, Mora R, Lutchen K, et al. Variable ventilation improves lung mechanics and gas exchange in a rodent model of acute lung injury. Am J Resp Crit Care Med 2000; 165: 366-71.
The purpose of this study is to determine the effects of variable ventilation on respiratory system of patients affected by acute respiratory distress syndrome.