Exploration of the effects on diaphragmatic electrical activity (EMG) and on respiratory pattern of various level of assistance delivered by the ventilator in intubated spontaneously breathing patients in pressure support (PS) and in Neurally Adjusted Ventilatory Assist (NAVA) by step by step increasing of the level of assistance. Flow, airway pressure, transesophageal EMG signal and transcutaneous EMG signal will be recorded.~Aims of the study:~To study the electrical diaphragmatic signal variations and the ventilatory profile variations under various level of assistance (delivered by the ventilator) in PS and in NAVA in intubated spontaneously breathing patients~To compare a non invasive technique of diaphragmatic electrical activity recording under various levels of assistance with the invasive reference technique
Exploration of the effects on diaphragmatic electrical activity (EMG) and on respiratory pattern of various level of assistance delivered by the ventilator in intubated spontaneously breathing patients in pressure support (PS) and in Neurally Adjusted Ventilatory Assist (NAVA) by step by step increasing of the level of assistance. Flow, airway pressure, transesophageal EMG signal and transcutaneous EMG signal will be recorded.