Blood volume measurement: The comparison of pulse dye densitometry and Dill and Costill's methods.

In many clinical situations, it is crucial to determine circulating blood volume (BV) easily and to repeat this measurement. The Dye DensitoGram Analyzer (DDG, Nihon Kohden Corp) measures semi-automatically BV, using an injection of IndoCyanine Green (ICG, 10 mg), and avoiding intermittent blood samples. The DDG was used during a 90-day microgravity simulation by Head-Down-Tilt bed rest (HDT) to measure BV and compared with the calculation of the plasma volume (PV) variations according to Dill and Costill's formula (DC). Seventeen healthy volunteers were included: 8 control subjects (Co) and 9 subjects submitted to a resistive exercise counter-measure (CM). Measurements were performed, one day before HDT, on days 3 and 90 of HDT and on day 9 after HDT. A double measurement of the BV was performed to assess the repeatability of this method. On the last day of HDT a significant decrease (p < 0.05) in the PV was noted with the DDG (Co: -12.3+/-5.7%, CM: -9.0+/-5.3%) and DC; (Co: -4.7+/-1.8%, CM: -6.8+/-2.5%). A good repeatability of the technique was shown with a low intrasubjects coefficient of variation (4.95+/-0.95%) and an acceptable intersubjects coefficient of variation (15.30+/-1.13%). No correlation was noted between DDG and DC (r2 = 0.27). The DDG gives a good repeatability, not affected by the microgravity exposure. Thanks to its capacity to measure accurately the BV within 7-10 min, this device presents major advantages for clinical use and research purpose.