• Monica Rocco, Gustavo Spadetta, Andrea Morelli, Donatella Dell'Utri, Patrizia Porzi, Giorgio Conti, and Paolo Pietropaoli.
• Department of Anesthesiology and Intensive Care, University of Rome La Sapienza, Viale del Policlinico 155, 00161 Rome, Italy. monica.rocco@uniroma1.it
• Intensive Care Med. 2004 Jan 1;30(1):82-7.

ObjectiveTo evaluate the reliability and clinical value of partial noninvasive CO2 (NICO2) rebreathing technique for measuring cardiac output compared with standard thermodilution in a group of intensive care nonpostoperative patients.Design And SettingClinical investigation in a university hospital ICU.PatientsTwelve mechanically ventilated patients with high (n=6) and low (n=6) pulmonary shunt fractions.Measurements And ResultsThirty-six paired measurements of cardiac output were carried out with NICO2 and thermodilution in patients ventilated in pressure-support mode and sedated with a sufentanil continuous infusion to obtain a Ramsay score value of 2. The mean cardiac output was: thermodilution 7.27+/-2.42 l/min; NICO2 6.10+/-1.66 l/min; r2 was 0.62 and bias -1.2 l/min+/-1.5. Mean values of cardiac output were similar in the low shunt group (Qs/Qt < 20), with r2=0.90 and a bias of 0.01 l/min+/-0.4; conversely, in the high pulmonary shunt group (Qs/Q > 35%) the mean was 9.32+/-1.23 l/min with thermodilution and a mean NICO2CO value was 6.97+/-1.53 l/min, with r2 of 0.38 and a bias of -2.3 l+/-1.2 min.ConclusionsThe partial CO2 rebreathing technique is reliable in measuring cardiac output in nonpostoperative critically ill patients affected by diseases causing low levels of pulmonary shunt, but underestimates it in patients with shunt higher than 35%.

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