Prediction Of Pulmonary Edema With Müller Maneuver

Plain-language summary

The mechanical ventilation weaning must begin as early as possible to limit its complications and requires a spontaneous breathing trial (SBT) before the separation from the ventilator to the patient. However, some patients fail this test and cannot be extubated. The main causes are pulmonary edema and diaphragmatic dysfunction. Predicting the risk of failure before carrying out the SBT makes it possible to anticipate a failure of the extubation and to adapt the therapies as well as possible. To assess the risk of pulmonary edema, cardiac preload, which corresponds to the end-diastolic filling volume of the ventricle, can be estimated using simple tests as the passive leg raising test before an SBT. However, this test requires tilting the patient's trunk and raising the lower limbs to 45°, and is not practical, especially in intensive care. The Müller maneuver, which allows maximum inspiratory pressure measurement via a one-way valve connected to the intubation tube, is currently used in routine care for diaphragmatic assessment. The endothoracic depression induced by this test is likely increasing venous return and cardiac output in patients with a reserve of preload, i.e. in preload-dependent patients. This test would be an easy alternative to the passive leg raising test used in current practice. The objectif is to assess whether the presence of an independant prelaod state, as detected by the absence of increased cardiac output during the Müller maneuver, is associated with the occurence of pulmonary edema during weaning from mechanical ventilation. The study consist in the measurement of cardiac output before and after the passive leg raising test and the Müller maneuver, then measurement of cardiac output before and after an SBT. A transthoracic ultrasound and a blood sample with dosage of proteins and hemoglobin will be carried out initially and then at the end of the SBT as part of routine care. The investigators hypothesize: * The Müller maneuver induces a greater increase in cardiac output in patients in a state of preload dependancy than in patients in a state of preload independancy. * The absence of documented preload dependancy during a Müller maneuver is associated with the occurrence of pulmonary edema during an SBT. The investigators included patients : * \> 18 years old, conscious patient, with health insurance, placed under mechanical ventilation for at least 24 hours ; * In whom it was decided to perform a passive leg raising test and an SBT. The investigators excluded pregnancy, patient with chest tube, particpation in another interventional study, tracheostomy, patient under legal protection.

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