Plethysmography uses blood pressure cuffs or other sensors attached to an instrument called a plethysmograph (or pulse volume recorder) to measure changes in the volume of a limb (or extremity). Because these volume changes are directly related to the amount of blood flowing through the limb, plethysmography helps to identify problems affecting blood circulation.

Arterial plethysmography may be used to rule out blockage of an artery in the leg or to identify problems in the smaller arteries in the hands, fingers, feet, and toes (such as Raynaud’s disease, a condition marked by abnormal constriction of blood vessels in the extremities upon exposure to cold or emotional distress).

Venous plethysmography helps to identify problems in blood flow through the veins in a limb or limbs. Venous plethysmography is most often performed to help identify or rule out a blood clot in a calf vein (deep vein thrombosis or DVT). It may also be used to detect dysfunction of important valves in the venous system causing blood to run backwards rather than forwards with exercise.

Purpose of the Plethysmography

  • To detect or rule out blockages (occlusion) and other circulatory problems in the extremities
  • To measure changes in blood flow or air volume

Who Performs It

  • A technician trained in vascular studies

Special Concerns

  • Venous plethysmography complements venous duplex scanning for identifying DVT in a calf vein.
  • Venous plethysmography is less accurate than venography for detecting DVT in general, but it is often done as an initial test to rule out DVT because it is noninvasive and easy to perform.
  • Arterial plethysmography is not as accurate as arteriography for detecting arterial blockages, but has the advantage of being noninvasive and easy to perform.

Before the Plethysmography

  • Do not smoke cigarettes for at least 30 minutes before the test begins, since nicotine constricts the peripheral blood vessels and can interfere with the accuracy of the results.
  • You will be instructed to remove all clothing from the limb or limbs being examined.

What You Experience

Arterial plethysmography:

  • You will be placed in a reclining position. You must remain still during the procedure.
  • Blood pressure cuffs or other sensors are placed at different locations on the arms, legs, fingers, and/or toes. (If cuffs are used, they are partially inflated to make them more sensitive to small changes in the circumference of the limbs corresponding to blood flow.)
  • The sensors record the pulse waves that occur with each heart beat. (This data is translated into a graphic recording for later review.)
  • In some cases, the test also records changes in pulsation under various conditions, such as exposure to cold or temporary stoppage of blood flow to the limb (which is done by inflating a blood pressure cuff in the upper region of the limb until the blood vessels collapse).
  • The test usually takes less than 20 to 30 minutes.

Venous plethysmography:

  • You will lie down on a bed or table. You must remain still during the procedure.
  • Blood pressure cuffs or other sensors are placed at different locations on one or both legs or arms. (If cuffs are used, they are partially inflated to make them more sensitive to small changes in the circumference of the limbs corresponding to blood flow.)
  • The sensors measure the volume of the limb before, during, and after blood flow is halted temporarily by inflating the uppermost cuff in the limb until the blood vessels collapse. (This data is translated into a graphic recording for later review.)
  • You may be asked to stand and perform certain stepping procedures as further recordings are taken.
  • The test usually takes less than 20 to 30 minutes.

Risks and Complications

  • This test is noninvasive and is not associated with any risks or complications.

After the Plethysmography

  • You may resume your normal activities.

Results

  • A physician will review the test data for evidence of abnormal blood circulation in the extremities.
  • If an abnormality is found, your doctor may recommend more invasive tests, such as arteriography or venography, to provide more information and establish a diagnosis.

Source:

The Johns Hopkins Consumer Guide to Medical Tests

Simeon Margolis, M.D., Ph.D., Medical Editor

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at Healthcommmunities.com

Published: 17 Jan 2012

Last Modified: 17 Jan 2012