Preliminary study to compare IntelliVent-ASV to conventional modes used from intubation to extubation or death in ICU patients requiring mechanical ventilation measuring duration of mechanical ventilation in order to design a multicenter large trial.

Inclusion criteria:

- Unselected ICU patients invasively ventilated for less than 24 hours, with an expected duration of MV longer than 48 hours.

Exclusion criteria:

• broncho-pleural fistula
• dyshemoglobulinémia
• moribund patient
• do-not-resuscitate order
• chronic respiratory failure requiring long term ventilation,
• patient ventilated more than 24 hours before admission,
• pregnancy,
• age below 18 years,
• protected patients,
• patient already participating in the study,
• Cheynes-Stockes breathing.
• Included patients with a treatment withdrawal decision within 24 hours after inclusion will be excluded,
• patients transferred to another ICU,
• patients needing ECMO, patients randomized to IntelliVent having less than 20% of time in IntelliVent-ASV.