Effective compliance of the total vascular bed and the intrathoracic compartment derived from changes in central venous pressure induced by volume changes in man.

In eight male subjects the blood volume was changed (± 10%) by hemorrhage and transfusion. One cycle of blood infusion and withdrawal or hemorrhage and reinfusion was completed within 9 minutes. The effective compliance of the total circulation was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume. The effective compliance was 2.3 ml/mm Hg kg "' body weight. This procedure was repeated while the capacity of the circulatory system was restricted by infusion of norepinephrine (15 /xg/min), lower body positive pressure, or both. The compliance values thus obtained were: norepinephrine 1.7 ml/mm Hg kg" body weight, lower body positive pressure 1.2 ml/mm Hg kg* body weight, and both norepinephrine and lower body positive pressure 0.9 ml/mm Hg kg~' body weight. The effective compliance of the intrathoracic vascular bed was assumed to be between 1.2 ml/mm Hg kg" body weight (lower body positive pressure) and 0.9 ml/mm Hg kg" body weight (norepinephrine and lower body positive pressure). These values constitute 55% and 42% of the effective compliance of the total circulation, respectively.