Plethysmography

Plethysmography is a type of medical testing that measures changes in volume within an organ or whole body, often resulting from fluctuations in blood flow. The term is derived from the Greek words plethysmos (increase) and graphy (writing).

History

The concept of plethysmography dates back to the 19th century, with the first documented use of the technique by Jean Leonard Marie Poiseuille in 1834. Poiseuille used a mercury-filled glass tube to measure changes in blood volume in the human body.

Types of Plethysmography

There are several types of plethysmography, including:

• Impedance plethysmography: This type measures changes in electrical impedance to determine blood flow.
• Optical plethysmography: This type uses light to measure changes in blood volume.
• Air displacement plethysmography: This type measures changes in air displacement to determine body composition.
• Photo-plethysmography: This type uses a light source and a photodetector to measure blood volume changes.

Applications

Plethysmography is used in a variety of medical fields, including cardiology, pulmonology, and sleep medicine. It can help diagnose conditions such as deep vein thrombosis, pulmonary hypertension, and sleep apnea.

Limitations

While plethysmography is a valuable tool in medical diagnostics, it has limitations. These include potential inaccuracies due to patient movement, variations in tissue composition, and the need for specialized equipment and trained personnel.

See Also

• Medical imaging
• Medical diagnosis
• Medical test