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).

Does resistance exercise prevent body fluid changes after a 90-day bed rest?

Although various exercise regimens are commonly used as countermeasures to reduce the cardiovascular deconditioning induced by microgravity, the underlying mechanisms are not well understood. In this study we aimed to test whether lower limb resistance exercise with flywheel technology can prevent the fluid homeostasis alterations induced by 90-day head-down tilt bed-rest (HDT), and thus improve orthostatic tolerance. Total body water (TBW, measured by isotope dilution) and plasma volume (PV, calculated from the haemoglobin and the haematocrit) were measured in a control group (Co, n=9) and a countermeasure group (CM, n=9).