Method for simultaneous determination of red cell and plasma flow velocity in vitro and in vivo

A method is described which can be used to simultaneously determine the flow velocity of plasma and of red blood cells in small glass tubes in vitro or in living microvessels of the microcirculation. The principle of dual slit photometry is applied to the measurement of plasma flow by determining the passage time of a dye bolus across two photodetectors separated by a variable distance. Measurements performed both in vitro and in vivo indicate a significant difference (up to 85%) between cellular and plasmatic flow velocity.