Spirometry

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:

1. FRC (RV + ERV)
2. TLC (TV + ERV + IRV + RV) = (VC + RV).

Recent exam question

FRC is the volume present in lungs:

1. After normal expiration
2. After forceful expiration
3. After deep inspiration
4. After normal inspiration.