Tidal volume (TV):
- Volume of air inspired/ expired during a normal quiet respiration
Inspiratory reserve volume (IRV):
- Volume of air inspired forcefully over and above a tidal inspiration with maximum effort
Expiratory reserve volume (ERV):
- Volume of air expired forcefully over and above a tidal inspiration, with maximum effort
Residual volume (RV):
- Volume of air which remains in the lungs at the end of a maximum expiration
Inspiratory capacity (IC): TV + IRV
Expiratory capacity (EC): TV + ERV
Functional residual capacity (FRC):
- Volume of air which remains in the lungs at the end of a normal expiration
- FRC= RV + ERV
Vital capacity (VC):
- Volume of air expired forcefully after a forceful inspiration is called vital capacity
- VC= IRV + TV + ERV
Total lung capacity (TLC):
- Maximum amount of air lung can contain
Note:
Any volume containing RV cannot be measured by routine spirometry. Ex:
- FRC (RV + ERV)
- TLC (TV + ERV + IRV + RV) = (VC + RV).
Recent exam question
FRC is the volume present in lungs:
- After normal expiration
- After forceful expiration
- After deep inspiration
- After normal inspiration.