Sedation During Noninvasive Ventilation (NIV)

In patients undergoing NIV for acute respiratory, lack of tolerance is one of the main reason of failure. This may result in a poor synchrony between the patient and the machine, leading to gross mismatching and potentially to an increased work of breathing. The investigators aim to investigate whether in these patients poorly responding to NIV the use of a sedation protocol using remifentanil will lead to an improve patient-ventilator interaction and better compliance to NIV.