Table of ContentsView AllTable of ContentsWhat It IsHow It Is MeasuredWhat It MeansWhen to Seek Care
Table of ContentsView All
View All
Table of Contents
What It Is
How It Is Measured
What It Means
When to Seek Care
Residual volume (RV) is the amount of air left in the lungs after you fully exhale. RV is one of several factors thatpulmonologistsmeasure duringpulmonary function testingto determine how well your lungs are working.
Normally, you need some air left in your lungs after an exhalation to keep the tiny air sacs calledalveoli—where oxygen and carbon dioxide are exchanged—open at all times. However, if the RV falls outside the expected value, it could be a sign of anobstructive lung diseaselike COPD an asthma orrestrictive lung diseaselike pulmonary fibrosis.
This article describes what residual volume is and why and how it is measured. It also explains what abnormal values mean and when it is time to see a healthcare provider.
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Why Do We Need Residual Volume?
Residual volume is needed because without some air in the lungs at all times, they would collapse. This, in turn, would cause the tissues of the airways to stick together, making the passages almost impossible to reinflate and keep open.
Residual volume is also important as it prevents fluctuations in oxygen and carbon dioxide levels in the lungs. By keeping the airways open, greater amounts of oxygen can enter the lungs and greater amounts of carbon dioxide can leave the lung. Neither oxygen nor carbon dioxide becomes “trapped” and accumulates.
How Is Residual Volume Measured?
Residual volume is the volume of air in the lungs in milliliters (mL) after a maximum exhalation. Unlike other pulmonary function tests, RV cannot be measured directly because you cannot empty your lungs completely.
Simply put:
By subtracting the amount of air forcibly exhaled following a normal breath from the amount of air left in the lungs after a breath, you would have an accurate measurement of the residual volume.
How the ERV Is Measured
For the ERV test, you will be asked to breathe in and out in a relaxed manner (called tidal breathing) for several moments. At the end of a normal exhalation, you will be asked to breathe with force into the spirometer. The volume of air expelled during this exhalation is your ERV.
The average ERV is about 1200 milliliters (mL) in males and 700 mL in females.
How the FRC Is Measured
The FRC is not as simple to measure as the ERV. FRC can be measured with one of two tests:
Of the two,body plethysmographyis more accurate but also more expensive and may not be available in some medical practices.
A normal FRC in most healthy adults is between 3000 mL and 4000 mL. Females tend to run along the lower range of values.
Clinical Significance of High and Low RV
Based on high or low levels, residual volume can help diagnose obstructive lung diseases (in which you have difficulty fully exhaling air from your lungs) or restrictive lung diseases (in which you cannot fully expand the lungs while inhaling).
RV values can also be used to monitor your response to treatment.
What High Residual Volume Mean
A high RV means that an abnormal amount of air is being retained in the lungs after you exhale. This is suggestive of obstructive lung diseases, most notably:
Low Residual Volume
A low RV means that you can only get a limited amount of air into your lungs due to the loss of lung capacity, volume, or strength. This is strongly suggestive of restrictive lung diseases like:
When to See a Healthcare Provider
If you are having trouble breathing, see a healthcare professional promptly. You may be asked to undergo lung function testing that includes calculations of residual volume and other factors that impact lung function—such as total lung capacity, functional residual capacity, tidal volume, and vital capacity.
In acute, severe cases, difficulty breathing can be an emergency. Call 911 immediately, as some causes of shortness of breath may be life-threatening.
Summary
Residual value (RV) is the amount of air left in the lung after maximum exhalation. It is calculated based on the results of spirometry and other pulmonary function tests.
A high RV is often seen with obstructive lung diseases like asthma and COPD, while a low RV is commonly seen with restrictive lung diseases like sarcoidosis and pulmonary fibrosis.
5 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Lutfi MF.The physiological basis and clinical significance of lung volume measurements.Multidiscip Respir Med.2017;12(3). doi:10.1186/s40248-017-0084-5Dunn JOC, Mythen MG, Grocott MP.Physiology of oxygen transport.BJA Educ.2016 Oct;16(10):341-348. doi:10.1093/bjaed/mkw012Dempsey TM, Scanlon PD.Pulmonary function tests for the generalist: a brief review.Mayo Clinic Proceedings.2018 Jun;93(6):763-771. doi:10.1016/j.mayocp.2018.04.009American Academy of Family Physicians.Office spirometry: indications and interpretation.Carlucci A, Poli BS.Getting it right in restrictive lung disease.J Clin Med.2023 May 9;12(10):3353. doi:10.3390/jcm12103353
5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Lutfi MF.The physiological basis and clinical significance of lung volume measurements.Multidiscip Respir Med.2017;12(3). doi:10.1186/s40248-017-0084-5Dunn JOC, Mythen MG, Grocott MP.Physiology of oxygen transport.BJA Educ.2016 Oct;16(10):341-348. doi:10.1093/bjaed/mkw012Dempsey TM, Scanlon PD.Pulmonary function tests for the generalist: a brief review.Mayo Clinic Proceedings.2018 Jun;93(6):763-771. doi:10.1016/j.mayocp.2018.04.009American Academy of Family Physicians.Office spirometry: indications and interpretation.Carlucci A, Poli BS.Getting it right in restrictive lung disease.J Clin Med.2023 May 9;12(10):3353. doi:10.3390/jcm12103353
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Lutfi MF.The physiological basis and clinical significance of lung volume measurements.Multidiscip Respir Med.2017;12(3). doi:10.1186/s40248-017-0084-5Dunn JOC, Mythen MG, Grocott MP.Physiology of oxygen transport.BJA Educ.2016 Oct;16(10):341-348. doi:10.1093/bjaed/mkw012Dempsey TM, Scanlon PD.Pulmonary function tests for the generalist: a brief review.Mayo Clinic Proceedings.2018 Jun;93(6):763-771. doi:10.1016/j.mayocp.2018.04.009American Academy of Family Physicians.Office spirometry: indications and interpretation.Carlucci A, Poli BS.Getting it right in restrictive lung disease.J Clin Med.2023 May 9;12(10):3353. doi:10.3390/jcm12103353
Lutfi MF.The physiological basis and clinical significance of lung volume measurements.Multidiscip Respir Med.2017;12(3). doi:10.1186/s40248-017-0084-5
Dunn JOC, Mythen MG, Grocott MP.Physiology of oxygen transport.BJA Educ.2016 Oct;16(10):341-348. doi:10.1093/bjaed/mkw012
Dempsey TM, Scanlon PD.Pulmonary function tests for the generalist: a brief review.Mayo Clinic Proceedings.2018 Jun;93(6):763-771. doi:10.1016/j.mayocp.2018.04.009
American Academy of Family Physicians.Office spirometry: indications and interpretation.
Carlucci A, Poli BS.Getting it right in restrictive lung disease.J Clin Med.2023 May 9;12(10):3353. doi:10.3390/jcm12103353
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