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What is Plethysmography?

Plethysmography is a diagnostic study that measures changes in the volume of air and blood in different parts of the body. These changes are measured by using blood pressure cuffs and sensors that are attached to a plethysmograph machine. The procedure is very useful in the screening and follow-up of patients with arterial or venous pathologies and lung disorders.

Types of Plethysmography

Plethysmography can be classified as:

1. Lung plethysmography: This procedure is also known as pulmonary or body plethysmography and helps to calculate the total lung capacity.

2.Limb plethysmography: This procedure helps to determine if there are blood clots in your arms or legs.

Indications of Plethysmography

Plethysmography may be indicated for patients with cardiovascular or lung conditions that are experiencing pain and discomfort while breathing and shortness of breath or are showing signs and symptoms of a blood clot in the extremities such as swelling, redness, or tenderness.

Preparation for Plethysmography

Specific instructions for the study will be given by your doctor. The general preparations include:

  • Avoid smoking or aerobic exercise 8 hours prior to undergoing the procedure.
  • Eat a light meal prior to the procedure as a heavy meal could affect your ability to breathe.
  • Wear loose-fitting clothing.
  • Inform your doctor about your regular medications, allergies, and if you have a fear of confined spaces.

Procedure of Plethysmography

Lung Plethysmography

  • You will be asked to sit in an airtight cabin similar to a phone booth with a glass window through which you can see the doctor.
  • Clips will be placed on your nose and a mouthpiece will be provided through which you must breathe.
  • Changes in the room pressure as you inhale and exhale will be recorded which helps to determine your lung capacity.
  • The procedure is completed in about 15-30 minutes.

Limb Plethysmography

  • You will be instructed to lie on you back on the examination table.
  • Blood pressure cuffs will be placed on one arm and one leg.
  • The highest blood pressure readings in the arm and the leg are recorded.
  • A very high difference between the readings could be an indication of a narrowing or blood clot in an artery or vein.
  • The procedure is completed in about 20-30 minutes.

Risks and Complications Associated with Plethysmography

Although plethysmography is a very safe procedure, there is a very minimal risk of:

  • Shortness of breath
  • Anxiety
  • Light-headedness or giddiness
  • Pain in arms and legs


Signet Heart Group
2800 North Highway 75
Sherman, Texas 75090


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Practice Hours: M-F 8am – 5pm

  • American Board of Internal Medicine
  • National Board of Echocardiography
  • Certification Board of Nuclear Cardiology
  • American Board of Vascular Medicine