Titration of Positive End-expiratory Pressure: Comparison Between Manual Thoracic or Abdominal Compression and Electrical Impedance Tomography

Patients with acute respiratory distress syndrome are placed on mechanical ventilation, and the adjustment of ventilator parameters is an important step in their care, in particular positive expiratory pressure, applied at the end of breathing. The goal of this study is to learn if continuous anterior chest compression works as well as electrical impedance tomography for positive expiratory pressure titration. Researchers will compare the two methods for each patient, in a randomly determined order : continuous anterior chest compression and electrical impedance tomography. Participants will : * have a pep titration with both techniques * be included in the study for 28 days