Acute cor pulmonale is one of deadly complications of mechanically ventilated acute respiratory distress syndrome (ARDS), which can lead to right ventricular dysfunction and worsen the hemodynamics of the patient. For several years, transthoracic (TTE) and transesophageal echocardiography (TEE) have replaced the pulmonary artery catheter to monitor cardiac function reliably and non-invasively.

Speckle tracking is an echocardiographic technique that allows a two-dimensional strain (2D) analysis of right ventricular systolic function. Right ventricular global strain (RVGLS) is a strain parameter, allowing an early and more accurate diagnosis of right ventricular dysfunction than conventional parameters.

This project will consist of performing TTE and TEE measurements at H0, 30min, H1, H2, and H24 after iNO administration in patient with ARDS under mechanical ventilation. The patient will be declared responder to iNO, if there is an increase of more than 20% of the PaO2/FiO2. 30 minutes after a dose of 10ppm of iNO.

Inclusion Criteria:

• Adult patient (age > 18 years)
• Hospitalized in the intensive care and post-operative care unit of the Amiens-Picardie University Hospital
• Patient with ARDS (defined by the Berlin criteria) requiring mechanical ventilation with a P/F ratio < 200 and requiring iNO
• Beneficiary of social security
• Signature of the consent to participate in the study by the patient or, if unconscious, his legal representative/next of kin

Exclusion Criteria:

• Pregnant or breastfeeding woman
• Contraindications to TEE (major upper gastro-intestinal surgery, mediastinal radiotherapy, active esophagitis, esophageal varices)
• Contraindications to the placement of an esophageal probe (recent upper gastro-intestinal surgery, active ulcer, active esophagitis)
• Presence of atrial fibrillation on echocardiographic examinations
• Contraindications to the administration of iNO
• Patients with chronic treatment allowing pulmonary arterial vasodilatation by sildenafil.