Inspiratory capacity (IC) is an important measurement of air volume in relation to your respiratory function or status. Inspiratory capacity is alungvolume measurement that is captured during apulmonary function test, which can be used to determine the mechanical function of your lungs.
This article will go over what inspiratory capacity is. You will learn how inspiratory capacity is measured as well as conditions that are associated with having reduced inspiratory capacity.
How Do Your Lungs Work?
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How Is Inspiratory Capacity Calculated?
While this volume can be measured through a pulmonary function test such asspirometry, it can also be calculated.
Inspiratory Capacity Formula
The calculation for inspiratory capacity is thetidal volume(the amount of air you casually breathe in) plus theinspiratory reserve volume(the amount of air you forcefully breathe in after a normal inhalation).
What Is an Expiratory Reserve Volume (ERV) Test?
Another way to calculate the inspiratory capacity is to take thetotal lung capacity(TLC), which includes forceful inspiration/exhalation and anyresidual air volumeleft in the lungs, and subtract thefunctional residual capacity, which includes only the volume forcibly exhaled and the residual volume in the lungs after.
This equation looks like this:TLC - FRC = IC
The average total lung capacity in an adult is approximately six liters, so the average IC/TLC is around 0.5 or 50%.
What Does Lung Consolidation Mean?
How Is Inspiratory Capacity Measured?
During the test, you will breathe through a mouthpiece in different ways. Sometimes you will breathe normally in a relaxed manner, while other times you will be asked to do more forceful breathing during inhalation or exhalation.
It is important that you follow the instructions to get accurate results from the test and learn about your inspiratory capacity. If you become tired, lightheaded, or do not understand the instructions, let the person conducting the test know.
How Are Incentive Spirometers Used?
Causes of Reduced Inspiratory Capacity
Reduced inspiratory capacity can happen for many reasons. Having difficulty breathing is typically related to two causes:
Obstructive and Restrictive Lung Disease Differences
In restrictive airway disorders, the lungs are not able to expand sufficiently to breathe as deep. This would decrease your inspiratory capacity.
In obstructive airway disorders, you are unable to fully exhale. If you are unable to fully exhale, you will have an elevated end-expiratory lung volume. With an increased volume remaining after normal exhalation, your lungs will not be able to breathe in as deeply and have a reduction in your inspiratory capacity.
What Is an FEV1/FVC Ratio in Spirometry?
Conditions Related to Inspiratory Capacity
Certain health conditions are related to inspiratory capacity. These conditions are categorized as showing a reduced inspiratory capacity or an increased inspiratory capacity.
How to Increase Lung Capacity Using Breathing Exercises
Reduced Inspiratory Capacity
Reduced inspiratory capacities are related to several diagnoses that are tied to the causes listed above. However inspiratory capacity is not used in the diagnosis of any breathing disorders.
Rather, it is used in monitoring symptoms and can be utilized in the prognosis of some disorders such aschronic obstructive pulmonary disease(COPD) when combined with the total lung capacity ratio.
While there are certainly more diagnoses related to restrictive and obstructive lung diseases, not all have evidence of the utility of inspiratory capacity.
What Happens During a Forced Vital Capacity (FVC) Test?
Summary
Inspiratory capacity (IC) measures how much air you can breathe into your lungs after you breathe out normally. Inspiratory capacity is usually measured during a pulmonary function test called spirometry.
On its own, your inspiratory capacity is not used to diagnose breathing problems but can be a useful way to monitor chronic lung diseases.
Frequently Asked Questions
Inspiratory capacity shows how much air you can breathe into your lungs after you have exhaled. This measure of air volume can help assess how well your respiratory system works.
For an adult, a normal inspiratory capacity is about 3 liters, or about 3,000 mL.
Inspiratory capacity is the maximum you can breathe in after you breathe out normally. Expiratory capacity is how much you breathe out forcefully.
FEV1 Is a Valuable Measure of Lung Function
9 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.East Tennessee State University.Lung Volumes and Capacities.National Library of Medicine.Physiology, Lung Capacity.American Thoracic Society.Pulmonary function tests.French A, Balfe D, Mirocha J, Falk J, Mosenifar Z.The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.Int J Chron Obstruct Pulmon Dis. 2015;10(1):1305-1312. doi:10.2147/COPD.S76739Panchabhai TS, Mireles Cabodevila E, Pioro EP, Wang X, Han X,Aboussouan LS. Pattern of lung function decline in patients with amyotrophic lateral sclerosis: implications for timing of noninvasive ventilation.ERJ Open Res. 2019 Sep 25;5(3):00044-2019. doi:10.1183/23120541.00044-2019Lee AS, Mira-Avendano I, Ryu JH, Daniels CE.The burden of idiopathic pulmonary fibrosis: An unmet public health need.Respiratory Medicine. 2014;108(7):955-967. doi:10.1016/j.rmed.2014.03.015Fernandez Fernandez E, De Santi C, De Rose V, Greene CM.CFTR dysfunction in cystic fibrosis and chronic obstructive pulmonary disease.Expert Rev Respir Med. 2018 Jun;12(6):483-492. doi:10.1080/17476348.2018.1475235American College of Allergy, Asthma and Immunology.Asthma-COPD Overlap.Centers for Disease Control and Prevention.Chronic Obstructive Pulmonary Disease.
9 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.East Tennessee State University.Lung Volumes and Capacities.National Library of Medicine.Physiology, Lung Capacity.American Thoracic Society.Pulmonary function tests.French A, Balfe D, Mirocha J, Falk J, Mosenifar Z.The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.Int J Chron Obstruct Pulmon Dis. 2015;10(1):1305-1312. doi:10.2147/COPD.S76739Panchabhai TS, Mireles Cabodevila E, Pioro EP, Wang X, Han X,Aboussouan LS. Pattern of lung function decline in patients with amyotrophic lateral sclerosis: implications for timing of noninvasive ventilation.ERJ Open Res. 2019 Sep 25;5(3):00044-2019. doi:10.1183/23120541.00044-2019Lee AS, Mira-Avendano I, Ryu JH, Daniels CE.The burden of idiopathic pulmonary fibrosis: An unmet public health need.Respiratory Medicine. 2014;108(7):955-967. doi:10.1016/j.rmed.2014.03.015Fernandez Fernandez E, De Santi C, De Rose V, Greene CM.CFTR dysfunction in cystic fibrosis and chronic obstructive pulmonary disease.Expert Rev Respir Med. 2018 Jun;12(6):483-492. doi:10.1080/17476348.2018.1475235American College of Allergy, Asthma and Immunology.Asthma-COPD Overlap.Centers for Disease Control and Prevention.Chronic Obstructive Pulmonary Disease.
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.
East Tennessee State University.Lung Volumes and Capacities.National Library of Medicine.Physiology, Lung Capacity.American Thoracic Society.Pulmonary function tests.French A, Balfe D, Mirocha J, Falk J, Mosenifar Z.The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.Int J Chron Obstruct Pulmon Dis. 2015;10(1):1305-1312. doi:10.2147/COPD.S76739Panchabhai TS, Mireles Cabodevila E, Pioro EP, Wang X, Han X,Aboussouan LS. Pattern of lung function decline in patients with amyotrophic lateral sclerosis: implications for timing of noninvasive ventilation.ERJ Open Res. 2019 Sep 25;5(3):00044-2019. doi:10.1183/23120541.00044-2019Lee AS, Mira-Avendano I, Ryu JH, Daniels CE.The burden of idiopathic pulmonary fibrosis: An unmet public health need.Respiratory Medicine. 2014;108(7):955-967. doi:10.1016/j.rmed.2014.03.015Fernandez Fernandez E, De Santi C, De Rose V, Greene CM.CFTR dysfunction in cystic fibrosis and chronic obstructive pulmonary disease.Expert Rev Respir Med. 2018 Jun;12(6):483-492. doi:10.1080/17476348.2018.1475235American College of Allergy, Asthma and Immunology.Asthma-COPD Overlap.Centers for Disease Control and Prevention.Chronic Obstructive Pulmonary Disease.
East Tennessee State University.Lung Volumes and Capacities.
National Library of Medicine.Physiology, Lung Capacity.
American Thoracic Society.Pulmonary function tests.
French A, Balfe D, Mirocha J, Falk J, Mosenifar Z.The inspiratory capacity/total lung capacity ratio as a predictor of survival in an emphysematous phenotype of chronic obstructive pulmonary disease.Int J Chron Obstruct Pulmon Dis. 2015;10(1):1305-1312. doi:10.2147/COPD.S76739
Panchabhai TS, Mireles Cabodevila E, Pioro EP, Wang X, Han X,Aboussouan LS. Pattern of lung function decline in patients with amyotrophic lateral sclerosis: implications for timing of noninvasive ventilation.ERJ Open Res. 2019 Sep 25;5(3):00044-2019. doi:10.1183/23120541.00044-2019
Lee AS, Mira-Avendano I, Ryu JH, Daniels CE.The burden of idiopathic pulmonary fibrosis: An unmet public health need.Respiratory Medicine. 2014;108(7):955-967. doi:10.1016/j.rmed.2014.03.015
Fernandez Fernandez E, De Santi C, De Rose V, Greene CM.CFTR dysfunction in cystic fibrosis and chronic obstructive pulmonary disease.Expert Rev Respir Med. 2018 Jun;12(6):483-492. doi:10.1080/17476348.2018.1475235
American College of Allergy, Asthma and Immunology.Asthma-COPD Overlap.
Centers for Disease Control and Prevention.Chronic Obstructive Pulmonary Disease.
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