We are going to conduct an interventional trial because of Peak Pressure measure, which is not measure in care practice. Following 18h of invasive mechanical ventilation in a controlled mode, the failure of the first single breathe trial of 2 hours and the presence of sevrability criterias defined by the European consensus conference in 2007, 80 participants will be included in the medical intensive care unit of Bordeaux's hospital. We'll perform measurements of the Maximal Inspiratory Pressure and Peak Pressure from the inclusion to the extubation.