 Cardiogenic shock, the most severe form of acute heart failure, is a critical situation where the body cells lack of oxygen because of cardiac dysfunction. The failure of pharmacological therapy to maintain adequate perfusion has led to attempts to improve the circulation by the use of mechanical circulatory support devices. Peripheral veno-arterial support PVA-ECMO is the most frequently used device. It consists of extracorporeal circulatory support. Venous blood is aspirated via the right atrium and reinjected into the descending aorta via the femoral artery. As a consequence of this by-pass, pulmonary artery flow and residual left ventricle ejection can fall drastically until zero in the most severe patients. A minimal transpulmonary blood flow is crucial to avoid left heart cavities and pulmonary artery and left heart cavities thrombosis. The gold standard technique to monitor transpulmonary blood flow is right-heart cavities catheterism Swan-Ganz catheter but it represents major limits: invasive technique, limited duration of utilization because of septic risk, physical limit of flow measurement under 1 literminute. End-tidal pressure carbon dioxide Pet CO2 monitoring or capnography is a routine and non-invasive measure in ventilated patients. Previous studies have shown that changes in PetCO2 can measure changes in cardiac output in anesthetized patients and that PetCO2 is a useful index of pulmonary artery blood flow during separation from cardiopulmonary bypass. The aim of this study is to demonstrate that PetCO2 is correlated to transpulmonary blood flow in patients under PVA-ECMO and that exhaled CO2 can provide an on-line, continuous, and noninvasive monitor of residual outflow from the heart during PVA-ECMO. 