COMPARISON BETWEEN CARDIAC-OUTPUT MEASURED BY THERMODILUTION TECHNIQUE AND CALCULATED BY O-2 AND MODIFIED CO2 FICK METHODS USING A NEW METABOLIC MONITOR

Objective: To calculate cardiac output from dual oximetry with carbon dioxide production (VCO2) and oxygen consumption (VO2) measured by a n ew metabolic monitor, and to compare these values with measurements ma de simultaneously using the thermodilution method during the steady st ate condition. Design: Prospective, comparative clinical study. Settin g: The adult postsurgical intensive care unit (ICU) of a University Ho spital, Patients: Twenty mechanically ventilated postsurgical patients (70.7 +/- 7.8 years of age; range 50-54). Measurements and results: A new metabolic monitor (Puritan-Bennett 7250, Carlsbard. USA) connecte d to a ventilator (Puritan-Bennett 7200) was used to measure VCO2 and VO2. Measurements of arterial (SaO(2)) and mixed venous (SvO(2)) oxyge n saturations were made using pulse and venous fiberoptic oximeters. C ardiac output starting from VCO2 (COVCO2) was obtained according to Ma hutte's formula: COVCO2 = VCO2/[k (SaO(2) - SvO(2))], where k represen ts a constant. The value for each patient was determined from the init ial measurements of thermodilution cardiac output (COtd), VCO2, SaO(2) and SvO(2). COVCO2 calculated from the previous equation was compared to the COtd. Cardiac output calculated from the traditional O-2 Fick equation (COVO2) was compared to the COtd. All patients were studied o ver a period of 120 min at 15-min intervals in reasonably stable condi tions. COVOC2 was closely related to COtd (r = 0.94; SEE = 0.79; p = 0 .0001; ii = 180) with a bias of 0.10 and a precision of 0.45 1/min. Th e mean percent difference between the two methods was -2.2 +/- 8.3 %. COVO2 was related to COtd (r = 0.77; SEE = 0.79; p = 0.0001; n = 180) with a bias of - 0.57 and precision of 0.86 1/min, The mean percent di ffer ence between the two methods was - 10.8 +/- 16.0 %. Conclusions: In stable patients, cardiac output measurements obtained from dual oxi metry with VO2 and VCO2 measured by this new metabolic monitor, show g ood correlation with measurements made using the thermodilution method . The values of cardiac output calculated from VCO2 are more accurate and precise than values from VO2. The validity of these measurements i n hemodynamically unstable patients and during various modes of mechan ical ventilation seems warranted.