Determination of Pulmonary Blood Volume by Single Intravenous Injection of One Indicator in Patients with Normal and High Pulmonary Vascular Pressures

Determinations of the pulmonary blood volume were carried out in 12 patients with pulmonary hypertension and in 12 patients with normal pressures in the pulmonary circulation, by the use of a single intravenous injection of one indicator, blood sampling being made through catheters in the pulmonary artery and left atrium and connected with two densitometers of similar characteristics. Pulmonary blood volume measured by this technic includes the major portion of, or the entire left atrial volume. Values obtained from duplicate or triplicate determinations performed in each patient have shown that this technic provides very good reproducibility of the results expressed by an average percentile variation around the mean equal to 3.2±2.7. The mean pulmonary blood volume as referred to body surface area was 375±97 ml./M. 2 for patients with pulmonary hypertension, and 310±21 ml./M. 2 for patients with normal pulmonary intravascular pressures. This difference was found to be significant ( p <0.05) but was attributed, at least in part, to a difference in the mean left atrial volume between the two groups studied. Some possible advantages and limitations of the method, as well as the poor correlation between pulmonary blood volume and other variables, like pulmonary intravascular pressures, stroke volume, and cardiac output, were discussed.