To take blood pressure using the lower leg and lower arm, the tester needs to measure systolic pressure at the ankle, then divide it by systolic pressure at the arm. This is known as the "Ankle Brachial Index," or ABI.Continue Reading
The Ankle Brachial Index is used to determine cardiovascular conditions, mortality and for the diagnosis of Peripheral Arterial Disease (PAD), as stated by Stanford School of Medicine.
Take the higher pressure of the two arteries at the ankle and divide by the brachial pressure from both arms. To calculate the pressure on the right side, this means taking the higher right ankle value and dividing by both brachial pressures. The same applies to the left side.