Volumetric monitoring: principles of application

The transpulmonary thermodilution indicator (TPID) technique has been recently introduced and diffuse in clinical practice. This "less-invasive" device measures intermittent cardiac output and, based on pulse contour method, continuous cardiac output, that agree with cardiac output obtained with pulmonary artery catheter in different clinical setting. Moreover it allowed stroke volume variation and pulse pressure variation experimental and clinically validate fluid responsiveness index in controlled mechanically ventilated patients. The TPID technique allowed an estimations of preload index such as intrathoracic blood volume and "lung edema" index as extra vascular lung water. We reviewed the principle of clinical application based on the current literature now available from this device. Cardiac output monitoring based on TPID technique is safe and accurate, as well as fluid responsiveness indicator (SVV and PPV). Intrathoracic blood volume seems to be a good preload index but the results reported in literature are not homogeneous in all its applications. Extra vascular lung water index is a very interesting parameter particularly in critically ill setting but its clinical application is not yet widely documented.