Measurement of Central Blood Volume by External Monitoring

Central blood volume was measured in 39 normal subjects, using external monitoring and interrupted arterial samples. The volume obtained by external counting was 15 per cent of the total blood volume, compared with 42 per cent obtained with the arterial curve. The importance of collimation and counter position was evaluated, and only with a dualcounter setup could a mean circulation time (MCT) for each ventricle be obtained. An MCT was necessary for satisfactory reproducibility of externally measured central blood volume. While the method has limitations, it does appear to offer a technique for measuring just the amount of blood in the heart and lungs with a satisfactory reproducibility, and would appear to be worth further application in problems involving measurement of central blood volume.