[A time-saving empirical method to calculate the area under dye dilution curves for the determination of cardiac output (author's transl)].

A simple and time-saving method is given for calculation of the area under dye dilution curves. The analysis of 415 dye dilution curves had shown that the area (A) under the curve, corrected for recirculation by semilogarithmic extrapolation and integrated by planimetry, could be approximated by the product of the concentration peak height (H) and the distance (t75) between the time of indicator appearance and the time of decay of indicator concentration to 75% of peak concentration: A = H.t75. The mean difference between cardiac outputs calculated from such "empirical" areas and from extrapolation-planimetry areas was 6.1 +/- 4.6% (n = 531). About 95% of the "empirical" values were within +/- 15% of the "planimetric" data. No systematic difference was observed for cardiac outputs from 50 to 350 ml/min/kg. Comparison of the presented method with other empirical methods shows, that the presented approximation of dye dilution curves has some advantages. The presented method (and all other empirical methods), however, should not be employed if high precision is required.