NON-INVASIVE MEASUREMENT OF CARDIOPULMONARY BLOOD-VOLUME - EVALUATION OF THE CENTROID METHOD

Abstract

Cardiopulmonary blood volume (CPV) and mean pulmonary transit time (MTT) determined by radionuclide measurements (99mTc HSA [human serum albumin]) were compared with values obtained from simultaneous dye-dilution (DD) studies (indocyanine green). The mean transit time was obtained from radionuclide curves by 2 methods: the peak-to-peak time and the interval between the 2 centroids determined from the right and left-ventricular time-concentration curves. Correlation of dye-dilution MTT and peak-to-peak time was significant (r = 0.79, P < 0.001), but its correlation with centroid-derived values was better (r = 0.86, P < 0.001). CPV values (using the centroid method for radionuclide technique) correlated significantly with values derived from dye-dilution curves (r = 0.74, P < 0.001). Discrepancies between the 2 were greater the more rapid the ciruculation (r = 0.61, P < 0.01), suggesting that minor inaccuracies of dye-dilution methods, due to positioning or delay of the system, can become magnified in hyperkinetic conditions. The radionuclide method is simple, repeatable and noninvasive and it provides simultaneous evaluation of pulmonary and systemic hemodynamics. Calculation of the ratio of cardiopulmonary to total volume can be used as an index of overall venous distensibility and relocation of intravascular blood volume.