All patients will be treated according to the sedation protocols and standards of care. Sedation will be guaranteed by continuous infusion of Propofol 2-4 ml / Kg / h, Remifentanil 0.05-0.1 mcg / Kg / min to obtain a RASS scale level of -5 of the RASS. Mio-resolution eventually obtained by a loading dose of 15 mg e.v. followed by a continuous infusion of 37.5 mg / h of besylated Cisatracury, will be reserved for patients with P/F <150.