Following was the data obtained from a patient:- Aerial BP = 90 mm Hg, cardiac output = 5.4 L/min. How much is the peripheral resistance?

By Ohm's law: Cardiac output (Q) = aerial BP/ peripheral resistance (R). Therefore, R = BP/CO Unit for peripheral resistance is PRU. 1 PRU = 1 mm Hg/mL/sec. That is, 1 PRU is 1 mm Hg when flow at the root of the aoa is 1 mL/sec. Thus, the unit for cardiac output will have to be conveed to mL/sec. 5.4 L/min = 90 mL/sec. Peripheral resistance (PRU) = 90 mm Hg/90 mL per sec. = 1 R.