Residual volume (RV)

Residual volume is the amount of air that remains in a person's lungs after fully exhaling. Health professionals use tests to measure a person's residual air volume to help evaluate 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 Updated: June 7, 2009

Author: Maria Essig

Medical Review: Caroline S. Rhoads, MD - Internal Medicine & Robert L. Cowie, MB, FCP(SA), MD, MSc, MFOM - Pulmonology

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