The purpose of this study is to determine if the left and right ventricular systolic function is involved in the development of weaning failure related to weaning-induced pulmonary edema.

Weaning from mechanical ventilation remains a central step in the management of critically-ill patients, since weaning failure and prolonged duration of mechanical ventilation are not only associated with an increase in the length of stay in intensive care but also with greater morbidity and mortality. One of the well-recognized causes of weaning failure is weaning-induced pulmonary edema (WIPO), which accounts for almost 60% of the causes of weaning failure and ranging up to 75% in high-risk patients, i.e. patients with medical history of chronic heart disease, chronic respiratory failure and obesity.

Echocardiography is increasingly used in intensive care and allows non-invasive assessment of diastolic function as well as left ventricular (LV) and right (RV) systolic function, including during a spontaneous breathing test. Although LV diastolic dysfunction appears to be a major determinant of WIPO, the role of LV and RV systolic dysfunction is less unequivocal and has been poorly studied so far. Scarce data showed that patients experiencing WIPO tended to exhibit more frequently LV systolic dysfunction, as demonstrated by a lower LV ejection fraction (LVEF) and no study but two have investigated the potential role of RV systolic function. Moreover, assessing LV systolic function with LVEF measurement suffers from several limitations, especially in critically-ill patients.

Thus, the main goal of this study is to investigate whether LV and RV systolic function is involved in the development of WIPO. The second goal of this study is to determine the best echocardiographic parameter to assess LV and RV systolic function during the weaning process.

Inclusion Criteria:

1. Invasive mechanical ventilation for more than 48 hours

2. Patients indicated, according to intensivists, for carrying out a spontaneous breathing trial weaning test, based on the presence of all of the following criteria:

   1. SpO2> 90% with FiO2 ≤40% and PEEP ≤5 cmH2O
   2. Cough effectiveness on tracheal aspirations
   3. Lack of hemodynamic instability and of disorders of consciousness

3. Patients at high risk of weaning-induced pulmonary edema (WIPO), defined by one or more of the following criteria:

   1. Obesity, defined by a body mass index> 30 kg/m²
   2. Chronic obstructive pulmonary disease
   3. Chronic heart disease

Exclusion Criteria:

1. Age <18 years and pregnant women
2. Patients with a decision of not to resuscitate
3. Poor echogenicity
4. Severe mitral valve disease (leakage and/or stenosis, bioprosthesis)
5. Patients with pacemaker
6. Tracheostomy
7. Chronic neuromuscular or neurodegenerative diseases

No plan is established

All echographic measurements will be analyzed offline, blinded to the patients' response to spontaneous breathing trial