- Pressure support test A pre-inclusion test (pressure support test) with a level of pressure support of ± 5 cmH2O of the previous level of positive inspiratroy pressure in the controlled mode (PCV for instance), but no greater than 30 cmH2O (pressure-support level plus positive end-expiratory pressure), is performed to evaluate if the patient's is ready to be weaned. The test could be stopped before 30 minutes if the patient showed evidence of respiratory distress (respiratory rate > 40 breaths per minute and FiO2 > 60% in order to obtain pulse oxymetry ≥ 95%) or apnea. The test will be performed again the day after if he still reach inclusion/exclusion criteria. The test is considered positive when, after 30 minutes, the patient remained clinically stable with a respiratory rate between 10 and 40 breaths per minute and an expiratory tidal volume higher than 6 ml per kilogram of body weight within the authorized pressure-support range, with pulse oxymetry no lower than 95 percent when the fraction of inspired oxygen was no greater than 60 percent. When the pressure-support test is positive, the patient is included in the study.