Cardiac output (CO) monitoring is recommended for the most serious and multiple-failure patients in critical care and allows the diagnosis of acute circulatory failure as well as its etiology and also allows the monitoring of treatments. However, although allowing an adaptation of hemodynamic treatments and being integrated into a therapeutic personalization approach in situations of acute circulatory failure, the measurement of CO is conditioned by the availability of devices, by their sometimes problematic invasiveness, as well as their cost. In addition, the discontinuous measurement of CO by echocardiography is made difficult in the context of resuscitation with patients who are less mobilizable and less echogenic.