Effect of Variable PSV in Acute Lung Injury: Part I and Part II

Noisy-PSV 1: different levels of variable pressure support (PS) will be randomized: a) PS variability equal to 0%, b) PS variability equal to 45%, c) PS variability equal to 90%.

Noisy-PSV 2 : different levels of variable Pressure Support (PS) will be randomized: a) PS equal to Baseline and variability 0%; b) PS equal to Baseline and variability set in order achieve an increase or decrease of pressure of 5 cmH2O; c) PS equal to Baseline - 5 cmH2O and variability 0%; d) PS equal to Baseline - 5 cmH2O and set in order achieve an increase or decrease of pressure of 5 cmH2O.