Ankle–brachial pressure index

Yes.

The most critical safety gateway before applying any compression is calculating the ankle brachial pressure index, or ABPI.

This involves using a Doppler ultrasound to compare the arterial blood pressure in the ankle to the blood pressure in the arm.

To see if the blood is making it down there.

Exactly.

It tells us how well the arterial system is perfusing the leg with fresh blood.

Okay, let’s go over the strict clinical thresholds for ABPI because this is where the textbook draws some very hard lines.

The rules are very, very clear.