Pulmonary intravascular blood volume changes through the cardiac cycle in healthy volunteers studied by cardiovascular magnetic resonance measurements of arterial and venous flow
Pulmonary blood volume increase during systole was measured in patients by analysing chest images obtained during ECG gated radionuclide angiography examination. The difference in the total radiation counts between systole and diastole in regions of interest, which included the lungs and the left ventricle, was measured and the relative pulmonary systolic blood volume increase (SBVI)-the ratio between the pulmonary SBVI and the cardiac stroke volume-was calculated. The relative pulmonary SBVI, which is a measure for the compliance of the pulmonary blood vessels, was found to be 0.26-0.85, and the average value was 0.57 +/- 0.15. The relative pulmonary SBVI was inversely correlated with the patient age (r = 0.27, p < 0.05) and with the left ventricular ejection fraction and stroke volume (r = 0.36, p < 0.01) due to decreased arterial compliance for older patients and for increased pulmonary blood volume respectively. The correlation coefficients were not high, indicating that the compliance of the patients is determined mainly by other individual factors. Radionuclide plethysmography enables qualitative assessment of pulmonary arterial compliance.