An algorithm to improve the estimation accuracy of a non-invasive method for cardiac output measurement based on prolonged expiration

Cardiac output (CO) monitoring is important inthe hemodynamic management of critically ill patients. In aprevious study, a novel non-invasive technique for COmonitoring based on prolonged expiration was proposed. Thenovel method showed good agreement with thermodilution onstable mechanically ventilated patients; unstable patients wereexcluded.The aim of this study is to improve the outcome of the abovementioned method on hemodynamic unstable patients,requiring vasoactive medications, and showing markedcardiogenic oscillations on waveforms related to expired gases.This prospective study has been carried out on three cardiacsurgery patients; eighteen CO measurements were performedon each patient, and these values were compared with dataobtained by thermodilution.The designed and tested algorithm allowed to reach a goodagreement between CO measured by our method and bythermodilution (e.g., the mean percentage differences were 4%,11% and 3%). Even though further validation is necessary, theresults are quite promising and the adopted solution appears toallow the suitability of the prolonged expiration method also on unstable patients