Basic Science

Blood is a non-Newtonian fluid, which means that it can be thicker in diastole than in systole by a multiple of 5 to 20x.  When moving slowly, as in diastole, the red blood cells aggregate and stack like coins into structures called rouleaux, making the blood thicker.  At systole, the red blood cells are disaggregated, making the blood thinner.  Because the heart is a pulsatile pump, blood viscosity rises and falls from one extreme to the other with every cardiac cycle – much like blood pressure.  Like blood pressure, a Blood Viscosity Profile is reported with two numbers:  Systolic Blood Viscosity and Diastolic Blood Viscosity. 

                        Blood pressure:  120/80 [mm Hg]

                        Blood viscosity:  40/200 [mP]