Lung volumes-
1. Tidal volume (TV) = ~500 ml
Definition: This is the amount of air you breathe in and out with each normal breath, typically around 500 ml.
2. Inspiratory residual volume (IRV) = ~3000 ml (3 Liter)
Definition: The extra air you can breathe in after a normal inhalation, about 3000 ml.
3. Expiratory residual volume (ERV) = ~1100 ml
Definition: The amount of air you can forcefully exhale after a normal breath, about 1100 ml.
4. Residual volume (RV) = ~1200 ml
Definition: The air that remains in your lungs even after you exhale maximally, around 1200 ml.
NOTE: RV can not measure through spirometer.
|
Lung capacity |
Formulas |
|
Inspiratory capacity (IC) |
IC = TV + IRV |
|
Expiratory capacity (EC) |
EC = TV + ERV |
|
Vital capacity (VC) |
VC = TV + IRV + ERV VC = IC + ERV |
|
Total lung capacity (TLC) |
TLC = TV + IRV + ERV + RV TLC = VC + RV TLC = IC + FRC |
|
Functional residual capacity (FRC) |
FRC = RV + ERV FRC = TLC - IC |
Lung capacity-
1. Inspiratory capacity (IC) = TV + IRV
Definition No. 1: IC is the maximum amount of air you can breathe in after normally exhaling.
Definition No. 2: Maximum volume of air forcefully inhaled after normal expiration.
2. Expiratory capacity (EC) = TV + ERV
Definition No. 1: EC refers to the maximum amount of air you can forcefully exhale after taking a normal breath.
Definition No. 2: Maximum volume of air forcefully exhaled after normal inspiration.
3. Vital capacity (VC) = TV + IRV + ERV = IC + ERV
Definition: TV representing the maximum amount you can forcefully exhale after a normal inhale.
4. Total Lung Capacity (TLC) = TV + IRV + ERV + RV = VC + RV = IC + FRC
Definition: Total amount of air your lungs can hold after a maximal forced inhalation.
5. Functional residual capacity (FRC) = RV + ERV = TLC - IC
Definition: The amount of air remaining in your lungs after a normal, passive exhalation.
FRC estimation-
1. Helium dilution method
2. Nitrogen Washout
3. Body Plethysmography
NOTE: Residual volume (RV) can't be measured through a spirometer, so lung capacities that contain RV also can't be measured through a spirometer.
1. Total Lung Capacity (TLC) = VC + RV
2. Functional residual capacity (FRC) = RV + ERV
So RV, TLC, FRC can't be measured through a spirometer.