Ankle:brachial index (ABI) is the ankle systolic pressure as determined by Doppler divided by the brachial systolic pressure. An abnormal index is 0.90. The sensitivity is approximately 90% for diagnosis of PVD.
Plethysmography measures changes in volume of toes, fingers, or parts of limbs that occur with each pulse beat as blood flows into or out of the extremity. This method may be used to determine toe pressures and pulse volume recordings, which are helpful when ankle pressures are falsely elevated because of calcified lower-extremity vessels. A toe:brachial index of 0.6 is abnormal, and values of 0.15 are seen in patients with rest pain (toe pressures of 20 mmHg).
Ultrasound:Doppler velocity, duplex, and color-flow Doppler are methods of evaluating artery stenosis and blood flow. These methods can localize and quantify the degree of stenosis. They are dependent on operator skill and are not as sensitive as the ankle:brachial index for screening purposes.
Transcutaneous oxygen tension measurements are useful in assessing tissue viability for wound healing. Measurements over 55 mmHg are considered normal and those below 20 mmHg are associated with nonhealing ulcers.
Exercise testing measures treadmill walking time and pre-exercise and post-exercise ankle:brachial indices. In those without significant PVD, the ABI is unchanged after exercise. In patients with PVD, the ABI falls after exercise. This testing is more sensitive for detecting disease than a resting ABI alone.