LUNG VOLUMES AND CAPACITIES
LUNG VOLUMES
Lung volumes are also known as respiratory volumes. It refers to the volume of gas in the lungs at a given time during the respiratory cycle.
1. Tidal volume(TV)
It is the amount of air which move in & out of the lung during quiet inspiration & quiet expiration
The normal adult value is 500mL
2. Inspiratory Reserve Volume(IRV)
It is an extra volume of air that can be inspired forcefully by the help of accessory inspiratory muscle after the end of normal inspiration.
The normal adult value is 3300mL.
3. Expiratory Reserve Volume(ERV)
It is an extra volume of air that can be expelled out forcefully after a normal expiration.
The normal value is 1000mL.
4. Residual Volume(RV)
It is the volume of air remaining in the lung even after forced expiration
The normal value is 1200mL.
LUNG CAPACITIES
Lung capacities are derived from a summation of different lung volumes.
1. Functional Residual Capacity(FRC)
It is the volume of air remaining in the lung after a normal tidal expiration.
FRC = RV + RRV
=1000mL+1200mL
=2200mL
=2.2L
2. Vital capacity(VC)
It is the maximum volume of air that can be exhaled out forcefully after a forceful inspiration.
VC = ERV + TV + IRV
=1000mL+500mL+3300mL
=4800mL
3. Inspiratory Capacity(IC)
It is the maximum volume of air that is inspired after a normal expiration.
IC = TV + IRV
=500mL+3300mL
=3800mL
4. Total Lung Capacity(TLC)
It is the volume of air present in the lung after forceful inspiration.
TLC = RV + ERV + TV + IRV
=1200mL+1000mL+500mL+3300mL
=6000mL
=6L
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