Deep Vein Thrombosis Diagnosis Plethysmography

DVT, or deep vein thrombosis, is a condition that occurs when a blot clot develops in one of the deep veins, which are the innermost veins of the body that lie within muscle tissue. These clots threaten a person’s health because they not only impede healthy circulation, but they also threaten to break free and lodge in other areas of the body. While clots usually form in the legs, DVT can occur in the arms and the pelvic region.

If left untreated, DVT can be fatal, namely if it causes pulmonary embolism (a condition in which a blood clot lodges in the lungs). As a result, early diagnosis of DVT is important for the best prognosis. A plethysmography, also called an arterial plethysmography, is one of a few diagnostic tests doctors use to diagnose DVT.

Other tests for diagnosing DVT include:

  • Doppler ultrasonography
  • magnetic resonance imaging (MRI)
  • venography.

How Does a Plethysmography Work?

A plethysmography is a test that measures systolic blood pressure. As the heart pumps blood, it creates pressure on the walls of the arteries. When your doctor takes your blood pressure, he uses a test that measures the amount of pressure that is being forced on the walls of the arteries.

The results of blood pressure tests come in the form of two numbers, for example 115/72 (“115 over 72,” when speaking). The first number, the systolic number, indicates the systolic blood pressure, or the maximum amount of pressure that the heart creates when it contracts. The second number measures diastolic blood pressure and indicates the force in your arteries when your heart is at rest.

During a plethysmography, a blood pressure cuff is placed on each arm, with a third blood pressure cuff wrapped around the upper leg. As the test proceeds, the medical caregiver notes differences in pressure between the arms and various parts of the leg. By comparing differences between blood pressure in the extremities, doctors can detect if blood clots are blocking areas in the arms or legs.

Types of Plethysmography

Doctors can choose between various types of plethysmography, including:

  • Body plethysmography: This type of plethysmography measures a patient’s lung capacity and strength. During a body plethysmography, the patient sits in a body box, also known as a body plethysmograph, that is sealed and airtight. Wearing a mouthpiece and a nose clip, the patient then performs various breathing exercises as instructed for about 20 minutes.

    After the test is over, the patient’s results are compared to the standard for people of the same sex, weight and age as the patient. The body plethysmography procedure is used to diagnose respiratory diseases and blood clots in the lungs (known as pulmonary embolism).

  • Impedance plethysmography: This plethysmography measures small fluctuations in the electrical resistance of a person’s arm and legs to determine if clots exist in deep veins. During an impedance plethysmography, doctors place two to four electrodes on the area of the body being tested. Measurements are taken when the pressure cuff is fully inflated and when the cuff is deflated.

The Pros and Cons of Plethysmography

One of the biggest benefits of using any type of plethysmography is that these tests are inexpensive, non-invasive ways to diagnose DVT. However, different types of plethysmography have their own unique downsides.

For example, impedance plethysmography can result in false negatives, meaning that doctors may have to retest a few times. In these cases, plethysmography may not be the most inexpensive way to diagnose DVT. Similarly, the con to the traditional plethysmography is that it too can be unreliable by returning false positives. Other tests are more accurate.

Consult your doctor and get all of the facts on each procedure before making a decision regarding the best test for you.

Resources

Answers.com (2007). Body Plethysmography. Retrieved July 18, 2007, from the Answers.com Web site: http://www.answers.com/topic/body-plethysmography?cat=health.

American Academy of Orthopaedic Surgeons (2007). Deep Vein Thrombosis. Retrieved July 19, 2007, from the AAOS Web site: http://orthoinfo.aaos.org/fact/thr_report.cfm?Thread_ID=264.

American Thoracic Society (1999). Diagnostic Approach to Acute Venous Thromboembolism. Retrieved July 19, 2007, from the American Thoracic Society Web site: http://ajrccm.atsjournals.org/cgi/content/full/160/3/1043.

Bupa (2007). Deep Vein Thrombosis. Retrieved July 18, 2007, from the Bupa Web site: http://hcd2.bupa.co.uk/fact_sheets/mosby_factsheets/Deep_Vein_Thrombosis.html.

National Heart and Lung Institute (2007). How is Deep Vein Thrombosis Diagnosed? Retrieved July 19, 2007, from the National Heart and Lung Institute Web site: http://www.nhlbi.nih.gov/health/dci/Diseases/Dvt/DVT_Diagnosis.html.

Enotes (n.d.). Impedance plethysmography. Retrieved July 19, 2007, from the Enotes Web site: http://health.enotes.com/nursing-encyclopedia/impedance-plethysmography.

University of Pennsylvania Health System (2007). Tests Blood Pressure. Retrieved July 18, 2007, from the University of Pennsylvania Web site: http://www.pennhealth.com/ency/article/003398.htm.

University of Pennsylvania Health System (2007). Ultrasound Plethysmography. Retrieved July 18, 2007, from the University of Pennsylvania Web site: http://www.pennhealth.com/ency/article/003771.htm.