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.
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