Physioflow® is a new device for measuring cardiac output in a non-invasive way using a thoracic bioimpedance technique. This technique has been validated in patients in stress tests as well as in Chronic Obstructive Pulmonary Disease (COPD) patients, in obese patients and in children. Very little work has been published in intensive care unit (ICU) and no studies have been done on hemodynamically unstable patients. The aim of this work is to compare the cardiac output measured by Physioflow® to the transthoracic echocardiography (TTE) in ventilated, sedated patients hospitalized in ICU receiving catecholamines and for whom the attending physician wants to evaluate the fluid responsiveness using the TTE and a passive leg raising maneuver (PLR).

All patients included will be simultaneously monitored with TTE and the Physioflow® thoracic electrical bioimpedance device. Cardiac output is measured by the Physioflow® Thoracic Bioimpedance Device and TTE before and after PLR. If the attending physician decide to administer fluid expansion a new set of cardiac output measurement will be performed before and after the volume expansion.

Inclusion Criteria:

• patient more than 18 year-old
• patient sedated and adapted to the assisted controlled ventilation
• patient receiving catecholamine (norepinephrine, epinephrine or dobutamine)
• patient requiring an haemodynamic evaluation by trans-thoracic echocardiography and PLR according to the attending physician

Exclusion Criteria:

• pregnant women
• patients with a poor echogenicity
• patients deprived of public law

Patient ≥18 year-old, sedated and adapted to the assisted controlled ventilation, receiving catecholamine (norepinephrine, epinephrine or dobutamine), requiring an haemodynamic evaluation by trans-thoracic echocardiography and PLR according to the attending physician.