Abbreviation for the peripheral resistance unit, used in physiology and medicine to assess blood flow in the capillaries. A measurement in PRU's is equal to the blood pressure in millimeters of mercury divided by the flow rate in milliliters per minute. That is, 1 PRU equals 1 mmHg·min/mL = 133.3 Pa·min/mL (or, in proper SI units, almost exactly 8 GPa s/m3)