The lung volume can be subdivided into physiologic subgroups seen during the respiratory cycle.
Capacities
|
Capacity |
Abbreviation |
Meaning |
|
functional residual capacity |
FRC |
volume of air remaining in the lungs at the end-expiratory level |
|
inspiratory capacity |
IC |
maximum volume of air inspired from the end-expiratory level |
|
inspiratory vital capacity |
IVC |
maximum volume of air inspired from the maximum expiratory level |
|
total lung capacity |
TLC |
volume of air in the lungs after maximum inspiration |
|
vital capacity |
VC |
maximum volume of air expired from the maximum inspiratory level |
Volumes
|
Volume |
Abbreviation |
Meaning |
|
expiratory reserve volume |
ERV |
maximum volume of air expired from the resting end-expiratory level |
|
inspiratory reserve volume |
IRV |
maximum volume of air inspired from the resting end-inspiratory level |
|
residual volume |
RV |
volume of air remaining in lungs after maximum expiration |
|
tidal volume |
TV |
volume of air inspired or expired with each breath during quiet breathing |
where:
• The minute ventilation (see below) is the tidal volume times the number of respirations per minute.
Equations Expressing Relationships
TLC =
= VC + RV
= IC + FRC
= IRV + TV + ERV + RV
= IRV + FRC + TV
VC =
= TLC - RV
= IC + FRC - RV
= IC + ERV
= IRV + ERV + TV
RV =
= FRC - ERV
= TLC - VC
= IC + FRC - VC
= IRV + TV + FRC - VC
IC =
= IRV + TV
= TLC - FRC
= VC - ERV
= VC + RV - FRC
FRC =
= ERV + RV
= TLC - IC
= TLC - IRV - TV
= TLC - VC + ERV
IRV =
= IC - TV
= TLC - FRC - TV
= VC - ERV - TV
= RV + VC - FRC - TV
ERV =
= FRC - RV
= VC - IC
= TLC - TV - RV - IRV
= VC - IRV - TV
TV =
= IC - IRV
= TLC - FRC - IRV
= VC - ERV - IRV
= RV + VC - IRV - FRC
Purpose: To determine unknown lung volumes if some values are known.
Specialty: Pulmonology
Objective: other testing
ICD-10: J44.9,
