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Residual Volume (RV)

Residual volume is the amount of air that remains in a person's lungs after fully exhaling. Doctors use tests to measure a person's residual air volume to help check how well the lungs are functioning.

Residual volume is measured by:

  • A gas dilution test. A person breathes from a container containing a documented amount of a gas (either 100% oxygen or a certain amount of helium in air). The test measures how the concentration of the gases in the container changes.
  • Body plethysmography. This test measures the total amount of air the lungs can hold (total lung volume). For this test, a person sits inside an airtight booth called a plethysmograph and breathes through a mouthpiece while pressure and air flow measurements are collected.

Last Revised: April 28, 2011

Author: Healthwise Staff

Medical Review: E. Gregory Thompson, MD - Internal Medicine & Mark A. Rasmus, MD - Pulmonology, Critical Care Medicine, Sleep Medicine

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