Method and apparatus for estimating hematocrit in a blood constituent processing system

Abstract From the Canadian patent

During an initial priming procedure, the blood draw/return needle(s) fluid flow system is primed with a nonblood fluid (e.g. a saline solution) having known fluid viscosity. The pressure drop occurring across the needle orifice(s) is determined at a known flow rate for this predetermined fluid of known viscosity. During subsequent blood constituent processing operations the pressure drop across the needle orifice is measured for a second known flow rate of blood constituents. From these measured relative values of pressure and flow rates, the blood viscosity value can be calculated and used to estimate (e.g. via a table look-up or analytical calculation procedure) a hematocrit value for the …