INDIRECT CALORIMETRY VERSUS PICK METHOD D ERIVED OXYGEN-UPTAKE DETERMINATION IN PIGS - INFLUENCE OF CARDIAC-OUTPUT

Objectives: To compare O-2 uptake values measured by indirect calorime try (V over dotO(2)R) with Fick-derived values (V over dotO(2)Fick) ov er a wide range of V over dotO(2) in experimental conditions and to an alyze the influence of cardiac output (Q over dotC) on the difference between V over dotO(2) and V over dotO(2)Fick. Study design: Animal st udy. Material: Nineteen 2.5-month-old, 29.2 +/- 2.8-kg, Large White pi gs. Methods: A step-by-step decrease in venous return was obtained eit her by haemorrhage or progressive inferior vena cava and portal veins clamping. Measurements, of 5 to 7 minutes duration included V over dot O(2)R (Deltatrac(TM)), thermodilution Q over dotC and arterial and mix ed venous blood On-content. The V over dotO(2) values were compared us ing Bland and Altman's bias analysis. The relationship between Q over dotC values and relative error (ER = [V over dotO(2)R-V over dotO(2)Fi ck]/0.5x[V over dotO(2)R+V over dot(2)Fick] was analyzed using a Spear man rank correlation coefficient. Results: The V over dotO(2)R and V o ver dotO(2)Fick arithmetic mean ranged from 108 to 253 mL . min(-1) in 130 measurements with broad limits of agreement between both methods. On average, V over dotO(2)R values were higher than V over dotO(2)Fic k values by +15 +/- 25 mL . min(-1). ER significantly decreased with Q over dotC (r(s) = 0.417; P = 0.0001). Conclusion: V over dotO(2)R val ues exceed V over dotO(2)Fick values. This bias does not occur in the low Q over dotC range, presumably owing to artifactual over estimation of thermodilution Q over dotC.