Understanding volumes and capacities of human respiratory system

Hyderabad: This article is in continuation to the previous article that focused on the human respiratory system. In this article, we will discuss the respiratory volumes and capacities:

Respiratory volumes and capacities
Tidal Volume (TV):

• Volume of air inspired or expired during a normal respiration. It is approximately 500 mL, i.e., a healthy man can inspire or expire approximately 6000 to 8000 mL of air per minute.
Inspiratory Reserve Volume (IRV):
• Additional volume of air a person can inspire by a forcible inspiration. This averages 2500 mL to 3000 mL.

Expiratory Reserve Volume (ERV):

• Additional volume of air, a person can expire by a forcible expiration. This averages 1000 mL to 1100 mL.
Residual Volume (RV):
• Volume of air remaining in the lungs even after a forcible expiration. This averages 1100 mL to 1200 mL. By adding up a few respiratory volumes described above, one can derive various pulmonary capacities, which can be used in clinical diagnosis.

Inspiratory Capacity (IC):

• Total volume of air a person can inspire after a normal expiration. This includes tidal volume and inspiratory reserve volume (TV IRV).
Expiratory Capacity (EC):
• Total volume of air a person can expire after a normal inspiration. This includes tidal volume and expiratory reserve volume (TV ERV).

Functional Residual Capacity (FRC):

• Volume of air that will remain in the lungs after a normal expiration. This includes ERV RV.
Vital Capacity (VC):
• The maximum volume of air a person can breathe in after a forced expiration. This includes ERV, TV and IRV or the maximum volume of air a person can breathe out after a forced inspiration.

Total Lung Capacity (TLC):

• Total volume of air accommodated in the lungs at the end of a forced inspiration. This includes RV, ERV, TV and IRV or vital capacity residual volume.
To be continued….