[Selection of a rational method of calculation of minute blood volume by the dye dilution curves]

In calculating the cardiac output on the basis of the dye dilution curves it is important to determine the area of the first circulation of the dye. The existing techniques of the determination of this area are different in their complexity and precision of the obtained results. A comparative evaluation of 14 techniques or their modifications for the determination of the cardiac output according to the Evans blue dilution curves was undertaken in 40 subjects (normal individuals and patients with chronic pulmonary pathology). A new method of calculations of the area by two triangles is suggested. The most precise techniques appeared to be the planimetric method of exponential extrapolation, the two and five triangles methods introduced by the authors, as well as the calculations of Hamilton and Simpson. It seems most rational to use the two and five triangles methods that are not only precise, but also simple. The method with five rectangular triangles should be preferred since it does not require any special equipment. In exceptional cases, in which the recirculation wave begins early and/or the direction of the descending portion is not clear, the Dow equation may be recommended, with the results multiplied by the factor of 1.26.