Blood flow studies measure blood flow and pressure.

There are different methods for performing blood flow studies.

A duplex study uses Doppler ultrasound to measure blood flow through arteries or veins. Clothing is removed from the area being tested. A probe with a conductive gel (like vasoline) on the tip is placed on various points along the blood vessel in question. The information is relayed to the ultrasound monitor to be viewed and recorded.

Plethysmography measures changes in blood volume in a blood vessel.Blood pressure is first taken in both arms. Clothing is removed from the arm or leg being tested. You lie on your back. A blood pressure cuff is applied to the limb being tested. It is inflated until the beat of the pulse is no longer heard. Then the pressure is released from the cuff. The blood pressure is then recorded and the information is put into a computer to interpret the information.

The blood pressure cuff may be moved to other positions on the same or other extremities during the test. After the readings are taken, you may be re-tested while in another position such as sitting or standing.

Clothing over the extremity will be removed just before the test. Tell the health care provider about medications you use, as they may alter blood flow.

During the plethysmography, the blood pressure cuff will constrict the arm or leg, but there is no pain. The gel used for the duplex ultrasound may feel cold when it is placed on your skin.

These are noninvasive (external) tests that will tell your doctor if there is disease in the arteries or veins, or if enough blood is reaching an arm or leg. The tests will look at injuries to blood vessels, or check patients with arterial reconstruction or grafts. These tests can also find blood clots.

As part of a duplex ultrasound, the doctor may calculate an ABI or ankle-brachial index. This number is obtained by dividing the pressure in the ankle by the pressure in the arm. A value of 0.9 or greater is normal. Your doctor will also check the flow of blood in the vessels with the ultrasound.

An ABI of less than 0.5 is linked to peripheral vascular (arterial) disease.

Other abnormal blood flow patterns can be seen with:

• Deep venous thrombosis (thrombophlebitis is an inflammation of a vein due to a blood clot)
• Superficial thrombophlebitis
• Communicating vein thrombophlebitis

These tests, or tests like them, may also be performed for additional conditions:

• Raynaud's phenomenon
• Stroke secondary to carotid dissection or carotid artery narrowing

There are no special risks associated with these tests.

Duplex/Doppler probe lets the technician view the vessels as well as measure the blood flow through them.