Plethysmography

Definition:

This test measures the systolic blood pressure (maximum pressure exerted when the heart contracts) of a lower extremity as compared to the upper extremity. The test is usually performed to rule out blockages in the extremities (usually lower extremities). (See also blood flow studies.)

Alternative Names:

Arterial plethysmography

How the test is performed:

This test may be done in the health care provider's office or in a hospital. You are placed in a partially propped-up position. Three blood pressure cuffs are wrapped snugly around the extremities. They are inflated to 65 mmHg (millimeters mercury), and a pulse volume recorder (plethysmograph) measures the pulse waves from each cuff. Any differences between the pulse waves are noted. If there is a reduction in any of the waves compared with the others, it may indicate a blockage. When the test is complete, the blood pressure cuffs are removed.

How to prepare for the test:

Refrain from smoking at least 30 minutes before the test. Remove all clothing from the extremities.

Infants and children:
The physical and psychological preparation a parent can provide for this or any test or procedure depends on the child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

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:

There should be minimal discomfort with this test. The pressure of the blood pressure cuff is all you should feel.

Why the test is performed:

The test is done to help rule out arterial blockages in the extremities.

Normal Values:

There should be less than 20 mmHg difference in the systolic blood pressure of the lower extremity compared to the upper extremity.

What abnormal results mean:

Abnormal results may indicate arterial occlusive disease, trauma to the arteries, small vessel diabetic changes, blood clots, and vascular diseases.

Additional conditions under which the test may be performed:

deep venous thrombosis

What the risks are:

There are no risks associated with this test.

Special considerations:

The test is not as accurate as an arteriography. This may be done for seriously ill patients who cannot be transported to the arteriography laboratory.

Review Date: 11/21/2001
Reviewed By: Steven Angelo, M.D., Department of Internal Medicine, Yale School of Medicine, Hospital of Saint Raphael, New Haven, CT. Review provided by VeriMed Healthcare Network.

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