US Patent 7879241 Method of treating a bodily fluid

A method of treating a bodily fluid withdrawn and then returned to a living body. The method involves withdrawing the bodily fluid from the living body and causing the bodily fluid to flow through a treatment system, altering at least the density of the bodily fluid through the action of a second fluid as the bodily fluid flows through the treatment system, sensing at least the density and flow rate of the bodily fluid before the density thereof is altered by the second fluid, sensing at least the density and flow rate of the bodily fluid after the density thereof is altered by the second fluid, sensing at least the density and flow rate of the second fluid, controlling the density and/or flow rate of the second fluid based on the sensed densities and flow rates, and returning the bodily fluid to the living body.