Blood flow studies

Alternative names

Duplex/Doppler ultrasound

Definition

Blood flow studies measure blood flow and pressure. A duplex study uses Doppler ultrasound to estimate blood flow through arteries or veins. Plethysmography measures changes in blood volume in a blood vessel.

How the test is performed

For the Duplex/Doppler ultrasound:
Clothing is removed from the area being tested, and 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.

For a plethysmography:
Blood pressure is first taken in both arms.

Clothing is removed from the arm or leg being tested. The patient lies on his or her back. A blood pressure cuff is applied to the limb being tested. It is inflated until the pulsatile flow is no longer heard. Then the pressure is released from the cuff until the flow returns. The blood pressure when flow returns is recorded and the information is transmitted to a computer which records and interprets 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, the patient may be re-tested while in another position such as sitting or standing.

How to prepare for the test

Clothing over the extremity being tested will be removed just before the test. Medications being used that can alter blood flow will be recorded before the test. In general, there is no other special preparation necessary for these tests.

For infants and children:

The preparation you can provide for this test depends on your child's age and experience. For specific information regarding how you can prepare your child, see the following topics:

• infant test or procedure preparation (birth to 1 year)
  
• toddler test or procedure preparation (1 to 3 years)
  
• preschooler test or procedure preparation (3 to 6 years)
  
• schoolage test or procedure preparation (6 to 12 years)
  
• adolescent test or procedure preparation (12 to 18 years)
  

How the test will feel
For 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.