Accuracy of Non-invasive Effective Pulmonary Perfusion Measurement by CO2

This is a prospective and observational study designed to test the accuracy and precision of the non-invasive capnodynamic cardiac output measurement in mechanically ventilated patients. We will study 30 patients undergoing cardiovascular by pass in which an invasive trans-thoracic thermodilution method (PICCOScience) is indicated - the reference method. A pair of thermodilutions and capnodynamic cardiac output measurement will be performed along the surgery. Analysis of precision will be done at the begining of the protocol and during stable hemodynamic conditions. Accuracy will then assessed using the Bland-Altmann plot and regression analysis.