Lung volumes

1. Lung volumes

2. Objectives
To know about different lung volumes and
capacities
To know how to measure them
And their significance in diagnosing lung
diseases

3. 4 volumes and 4 capacities
Tidal volume
Inspiratory
reserve volume
Expiratory
reserve volume
Residual volume
Vital capacity
Inspiration
capacity
Functional
residual capacity
Total lung
capacity

4. THESE ARE MEASURED USING A TECHNIQUE CALLED
SPIROMETRY
INDIRECT SPIROMETRY USING HELIUM DILUTION
TECHNIQUE IS USED TO MEASURE FRC THOUGH WHICH
RV AND TLC ARE DERIVED
DIRECT SPIROMETRY CAN MEASURE ALL THE
REMAINING LUNG VOLUMES AND USED TO DERIVE
OTHER LUNG CAPACITIES

5. Tidal volume
“The tidal volume (TV) is the volume of air that is drawn into
the lungs during inspiration from the end-expiratory position
(and also leaves the lungs passively during expiration) in the
course of quiet breathing.”
Normal value = 6-8 ml/kg

6. Inspiratory reserve volume
The maximum amount of air that can be
inhaled after a normal tidal volume
inspiration
Normal value 1900-3300ml

7. Expiratory reserve volume
“The expiratory reserve volume (ERV) is the maximum
volume of air that can be forcibly exhaled after a quiet
expiration has “been completed (i.e., from the end-
expiratory position).”
Normal value is 700 -1000 ml

8. Residual volume
“The residual volume (RV) is the volume of air that
remains in the lungs after a maximal expiratory effort.
Set by balance b/w actions of expiratory muscle & recoil
forces of lung which act to decrease lung volume & outward
recoil forces of chest wall devouring lung expansion
Normal value is

9. Vital capacity
Volume of air that can be exhaled from lungs after maximum inspiration
Vital capacity =IRV + TV + ERV
Normal value is 60-70ml /kg

10. Inspiratory capacity
Maximum amount of air that can be
inhaled from end of tidal volume i.e from
a normal expiratory position
 INSPIRATORY CAPACITY= IRV + TV

11. Functional residual capacity
“The functional residual capacity (FRC) is the volume of air
that remains in the lungs at the end of a normal
expiration.”
FRC = ERV+ RV

12. Total lung capacity
“The total lung capacity (TLC) is the total volume of air contained in the lungs a
the end of a maximum inspiration.”
TOTAL LUNG CAPACITY = IRV + TV + ERV + RV
 It “is determined by the balance between the force-generating capacity of the inspiratory muscles and the
opposing elastic recoil forces of the lung and chest wall.
 Weakness of the muscles of inspiration or increased stiffness of the lung reduces TLC.
 Loss of retractive forces exerted by the lung, as in emphysema, enlarges TLC.”

13. Normal values at a glance (for a 20yr old healthy
seated make)
 Tidal volume=0.6L
 Residual volume=1.4L
 E.R.V= 1.9L
 I.R.V= 3.0L
I.C=3.0L
F.R.C=3.2L
T.L.C= 6.3 L
V.C= 4.8 L

15. Thank you