Methodologic variability of pulmonary-left heart blood volume by dye dilution in dogs

¹ Cardiovascular Institute, Michael Reese Hospital and Medical Center, Chicago, Illinois

This study was done in order to estimate the methodologic variability (MV) of a dye-dilution technique for determining the combined pulmonary-left heart volume. "Clusters" consisting each of four slug curves shot in rapid succession were obtained under conditions in which great effort was made to suppress hemodynamic variation. Six clusters, during which the mean aortic and mean pulmonary artery pressures, the left ventricular end-diastolic pressure, heart rate, and cardiac output remained relatively stable, were selected for analysis on the assumption that the true volume under study also varied but little. In these selected clusters the variation in calculated volume was determined, and this variation considered to be the MV. The value for MV thus obtained is of course an overestimate and, expressed as one standard deviation, ranged from 1.6 to 6.6%, and averaged 3.8% of the mean value. The meaning and applicability of methodologic variability is discussed. A convenient method for calculating mean transit time from slug data is described.

Key Words: pulmonary blood volume • blood volume methodology • methodologic reproducibility • dye-dilution technique

Submitted on January 29, 1965