Question

discuss lungs volumes and capacities

Answer 1

1)Tidal volume (TV)

Amount of air inhaled or exhaled in one breath during relaxed, quiet breathing.
Volume 500-750 ml

2)Inspiratory reserve volume (IRV)
Amount of air in excess of tidal inspiration that can be inhaled with maximum effort.
Volume is 2000 ml

3)Expiratory reserve volume (ERV)
Amount of air in excess of tidal expiration that can be exhaled with maximum effort.
Volume 1000 ml

4)Residual volume (RV)
Amount of air remaining in the lungs after maximum expiration; keeps alveoli inflated between breaths and mixes with fresh air on next inspiration.
Volume is 1300 ml

It cannot be measured by spirometry.

5)Closing volume (CV)
It is Close to RV
It is the lung volume above the residual volume at which airway in the lower, dependent parts of the lungs begin to close.

6)Forced expiratory volume (FEV1)
FEV1 is the volume of air that can be expired in the first second of a forced maximal expiration.
FEV1 is normally 80% of the forced vital capacity, which is expressed as:
FEV1/ FVC = 0.8

In obstructive lung disease, such as asthma, FEV1 is reduced more than FVC so that FEV1/FVC is decreased.

In restrictive lung disease, such as fibrosis, both FEV1 and FVC are reduced and FEV1/FVC is either normal or is increased.

Lung capacities
1.Inspiratory capacity
It is the sum of tidal volume and IRV(Tv+IRV)

2.Functional residual capacity (FRC)
It is the sum of ERV and RV.(ERV + RV)
It is the volume remaining in the lungs after a tidal volume is expired.
It includes the RV, so it cannot be measured by spirometry.

3.Vital capacity (VC), or forced vital capacity (FVC)= ( Tv+ IRV + ERV)

It is the sum of tidal volume, IRV, and ERV.
It is the volume of air that can be forcibly expired after a maximal inspiration.

4. Total lung capacity (TLC)
TLC= TV+ IRV + ERV+ RV
It is the sum of all four lung volumes.
It is the volume in the lungs after a maximal inspiration.
It includes RV, so it cannot be measured by spirometry.