Justification: The diaphragm is the main inspiratory muscle. Its dysfunction therefore compromises ventilation, which is necessary for gas exchange. Diaphragmatic dysfunction is frequently observed in resuscitation patients. Diaphragm ultrasound is currently a simple and validated technique for measuring the function of the diaphragm in intensive care. However, the discontinuity of the measurements is one of the major limitations of the current, standard ultrasonic evaluation of diaphragm function. Respinor AS (Oslo, Norway) has developed an ultrasound device (known as RESPINOR DXT) for continuous quantification of diaphragmatic excursion and velocity.

Aims of the study: To evaluate the feasibility of the continuous monitoring of the diaphragmatic excursion using RESPINOR DXT in patients undergoing MV in the intensive care unit, to ensure its reliability and to establish a link between the diaphragmatic excursion and the weaning outcome of MV.

Method: In addition to continuous diaphragm monitoring by RESPINOR DXT, a daily measurement of the diaphragm excursion will be performed using a conventional ultrasound system for comparison. A daily measurement of the oesophageal pressure (Pes) and the gastric pressure (Pga) will be performed, thus allowing the calculation of the transdiaphragmatic pressure (Pdi).

Analysis: The feasibility of the measurement will be evaluated through user utility questions as well as the time spent with a signal meeting specific quality criteria. Its reliability will be studied by the concordance between the measurements of the excursion measured by RESPINOR DXT and by standard ultrasound (Bland-Altman, Passing-Bablock). It will be further evaluated by the correlation between the variations of the excursion measured by RESPINOR DXT and the Pdi variations. Receiver operating characteristic (ROC) curves will be performed to identify the optimal diaphragmatic excursion threshold for predicting weaning success and prognosis.

Hypothesis: It is anticipated that the present study will show that the continuous monitoring of diaphragm excursion by RESPINOR DXT is reliable. Further, it is anticipated that there will be a statistical link between the diaphragmatic excursion and velocity of the movement measured by RESPINOR DXT before, during and after the spontaneous breathing trial.

Inclusion Criteria:

• Over 18 years old
• Consent to participate in the study
• Affiliation to a social security scheme or entitled to it
• Invasive mechanical ventilation for ≥ 24 hours
• Richmond Agitation Sedation Scale (RASS) ≥ - 3 (Moderate sedation)
• Able to tolerate spontaneous ventilation with inspiratory support ≤ 28 cmH2O
• Absence of high-dose vasopressors defined by noradrenaline dosage < 0.3 μg / kg / min

Exclusion Criteria:

• Central or spinal neurological lesion involving central ventilatory control or its transmission
• Contraindication to the insertion of the oesophageal catheter, ie any contraindication to insertion or change of gastric tube, esophageal surgery of less than 14 days, oesophageal varices rupture of less than 4 days
• Known neuromuscular disease, curare less than 24 hours (excluding succinylcholine for rapid sequence intubation), known hemidiaphragm paralysis or suspicion of hemidiaphragm paralysis (defined by elevation) dome> 2.5 cm compared to contralateral dome
• Patient in therapeutic limitation
• Pregnant woman, minor patient or protected adult

Patients on mechanical ventilation in the intensive care unit for greater than 24 hours