Key result
New assumed oxygen consumption formula outperforms LaFarge and Miettinen with a ~2 ml/min mean difference.
Why the study?
Differences had been observed between dye dilution cardiac output and Fick cardiac output calculated from estimated oxygen consumption using LaFarge and Miettinen formulae, prompting the search for a better formula.
Does a new regression formula improve the accuracy of assumed oxygen consumption compared to the LaFarge and Miettinen formulae in patients undergoing right and left heart catheterization?
Observational (n=310)
Does a new regression formula improve the accuracy of assumed oxygen consumption compared to the LaFarge and Miettinen formulae in patients undergoing right and left heart catheterization?
Absolute Event Rate: 2% vs -21.8%
p-value: p=0.771
A newly derived formula for assumed oxygen consumption provides better agreement with actual values derived from dye dilution cardiac output than the traditional LaFarge and Miettinen formulae.
New assumed VO2 formula may narrow dye-Fick discrepancies in cath labs; leaves open prospective validation before routine adoption.
This study was performed because of observed differences between dye dilution cardiac output and the Fick cardiac output, calculated from estimated oxygen consumption according to LaFarge and Miettinen, and to find a better formula for assumed oxygen consumption. In 250 patients who underwent left and right heart catheterization, the oxygen consumption VO2 (ml.min-1) was calculated using Fick's principle. Either pulmonary or systemic flow, as measured by dye dilution, was used in combination with the concordant arteriovenous oxygen concentration difference. In 130 patients, who matched the age of the LaFarge and Miettinen population, the obtained values of oxygen consumption VO2(dd) were compared with the estimated oxygen consumption values VO2(lfm), found using the LaFarge and Miettinen formulae. The VO2(lfm) was significantly lower than VO2(dd); -21.8 +/- 29.3 ml.min-1 (mean +/- SD), P < 0.001, 95% confidence interval (95% CI) -26.9 to -16.7, limits of agreement (LA) -80.4 to 36.9. A new regression formula for the assumed oxygen consumption VO2(ass) was derived in 250 patients by stepwise multiple regression analysis. The VO2(dd) was used as a dependent variable, and body surface area BSA (m2). Sex (0 for female, 1 for male), Age (years), Heart rate (min-1) and the presence of a left to right shunt as independent variables. The best fitting formula is expressed as: VO2(ass) = (157.3 x BSA + 10.0 x Sex - 10.5 x In Age + 4.8) ml.min-1, where ln Age = the natural logarithm of the age. This formula was validated prospectively in 60 patients. A non-significant difference between VO2(ass) and VO2(dd) was found; mean 2.0 +/- 23.4 ml.min-1, P = 0.771, 95% Cl = -4.0 to +8.0, LA -44.7 to +48.7. In conclusion, assumed oxygen consumption values, using our new formula, are in better agreement with the actual values than those found according to LaFarge and Miettinen's formulae.
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Bergstra et al. (1995) conducted an observational in Patients undergoing left and right heart catheterization (n=310). New regression formula for assumed oxygen consumption vs. LaFarge and Miettinen formulae was evaluated on Difference between assumed and actual oxygen consumption (95% CI -4.0 to +8.0, p=0.771). A new regression formula for assumed oxygen consumption showed better agreement with actual values (mean difference 2.0 ml/min; 95% CI -4.0 to +8.0; P=0.771) than the LaFarge and Miettinen formulae.