Lung volumes

1. Dr.S.Roopa,MD,DMCH
,
FAIMER Fellow &
Associate Professor
Dept of Physiology
Lung volumes & Capacities

2. Objectives
1. Different lung volumes and capacities.
2. Clinical significance of vital capacity

3. Lung volumes & Capacities
Defined as volume of gas in the lungs at
different levels of respiratory act

4. VENTILATION PARAMETERS
LUNG VOLUMES
1.Tidal volume (TV)
2.Inspiratory Reserve
volume (IRV)
3.Expiratory Reserve
volume (ERV)
4.Residual volume (RV)

5. Tidal volume (TV)
Volume of air inspired or expired during
one respiratory cycle.
Adults : 500 ml
Newborn: 10-20 ml; Children:150-300 ml
Tidal volume is increased during muscular
activity.

6. If I’m breathing normally, then I’m
breathing at. . .
• Tidal volume
– ~ 500 mL
• Which one is it?
Tidal
volume

7. Inspiratory Reserve Volume (IRV )
The maximum volume of air that can be
inspired by a forced inspiration after a
normal inspiration.
Normal Value : 3000 ml

8. ADDITIONAL volume inspired above
tidal volume
Which one is it?
IRV

9. Expiratory Reserve volume (ERV )
The maximum volume of air that can
be expired by a forceful expiration
after a normal expiration.
Normal Value : 1100 ml

10. ADDITIONAL volume of air expired
BELOW tidal volume
• Which one is
Expiratory
Reserve Volume?
ERV

11. Residual volume (RV)
Volume of air that remains in the lungs
at the end of a maximal expiration
Normal Value: 1200 ml

12. Residual Volume
• How much air is
left in the lungs
after the subject
has forcefully and
maximally expired
• CANNOT BE
MEASURED BY
SPIROMETRY RV

13. Lung capacities
Sum of two or more volumes = Capacities
1.Inspiratory capacity
(TV + IRV )
2.Vital capacity
(TV+IRV+ERV)
3.Functional residual
capacity (RV+ERV)
4.Total lung capacity
(TV+IRV+ERV+RV )

14. 1. Inspiratory capacity (TV + IRV )
Maximum volume of air that can be inspired by
forced inspiration after a normal expiration.
Normal Value: 3500 ml

15. 2. Vital capacity (VC ) (TV+IRV+ERV)
Maximum volume of air that can be expelled by a
complete expiration after a maximum inspiration
Normal Value : 4600 ml

16. Factors influence vital capacity
1. Respiratory muscle power
2. Airway patency (resistance)
3. Compliance of the lungs
4. Elasticity & viscosity of lung

17. VC increased in:
1.Divers
2.Swimmers
3.Trained Athletes
4.Standing posture

18. VC Decreased in:
Physiological
1. Old age
2. Lying posture
3. Obesity
Pathological
1.Asthma
2.Emphysema
3.Pleural effusion
4.Fibrosis
5. Poliomyelities

19. 3. Functional residual capacity (FRC ) (RV+ERV )
Volume of air remaining in the lungs at the
end of a normal expiration.
Normal value: 2300ml
FRC: Physiologically important

20. Significance of FRC
1. - If there was no FRC, the lungs will be
completely emptied during each respiratory
cycle
- The alveolar PO2 & PCO2 will vary widely &
interfere with diffusion of respiratory
gases. Thus it helps in providing O2 without
fluctuations ie. it acts as a buffer against
fluctuations
2. It prevents collapse of the lungs.
3. Breath holding is made possible due to FRC

21. 4. Total lung capacity
(TV+IRV+ERV+RV )
Volume of air contained in the lungs at the
end of a maximal inspiration.
Normal Value : 6000ml

23. Lung volumes & capacities-normal values
• Tidal Volume: 500 ml
• Inspiratory Reserve Volume: 2500 – 3000 ml
• Expiratory Reserve Volume: 1000 – 1200 ml
• Residual volume: 1000 - 1200 ml
• Inspiratory Capacity: 3 - 3.5 L
• Functional Residual Capacity: 2.5 L
• Vital Capacity: 3.8 – 4.5 L
• Total Lung Capacity: 6 L

25. Fraction of vital capacity that is expelled with
maximal effort in unit time
• FEV1 - 80% of Vital Capacity (an index for
obstructive lung diseases)
• FEV2 - 90% of Vital Capacity
• FEV3 - 97% of Vital Capacity
Timed Vital Capacity

26. Forced Vital Capacity (FVC)
• Vital Capacity recorded on a
fast moving drum
Forced Expiratory Volume
(FEV1)
• Volume of air forcefully
expired from full inflation
(TLC) in the first second
• Normal people can exhale
more than 75-80% of their
FVC in the first second
• FEV1/FVC ratio can be
utilized to characterize lung
disease

27. Restrictive Lung
Disease
• Characterized by
diminished lung volume.
• Eg: Interstitial lung
disease, Pleural effusion
• Decreased TLC
• Both FVC, FEV1 are
decreased
• FEV1/FVC ratio:
Normal or Increased
Obstructive lung
disease
• Characterized by
obstruction to
expiratory airflow.
• Eg: Asthma, COPD
• Normal TLC
• Disproportionate
reduction in FEV1
• FEV1/FVC ratio:
Decreased

28. Obstructive
Diseases
Restrictive
Diseases
FEV1  
FVC  
FEV1/ FVC
ratio  Normal (or) 

31. Spirometer

32. Probable Qs
Essay:
• Define various lung volumes and capacities
with a diagram. Give the normal values.
Short notes:
• Vital capacity
• Timed vital capacity or Forced vital
capacity
• Functional residual capacity

33. MCQs
• The normal value of Tidal volume is
_____
• FEV1/ FVC ratio is reduced in ____
• FEV1/ FVC ratio is normal/increased
in ____

34. Summary
1. Tidal volume – volume of air
inspired or expired during one
respiratory cycle (500ml)
2. Expiratory reserve volume – the
air expelled with maximal
expiratory effort after
normal expiration (1000 - 1200
ml)
3. Inspiratory reserve volume – the
air inspired with maximal
inspiratory effort after
normal inspiration (2500 –
3000 ml)
4. Residual volume – the volume of
the air in the lungs after the
maximal expiratory effort
(1000 - 1200 ml)
5. Vital capacity – the maximal
volume of air that can be
expelled from the lungs by
forceful expiration after a
maximal inspiration
(TV+IRV+ERV) (3.8 – 4.5 lts)
6. Inspiratory capacity- the
maximal volume of air that can
be inspired from the resting
expiratory level (TV + IRV) (3
– 3.5 lts)
7. Functional residual capacity –
the volume of air remaining in
the lungs at the resting
expiratory level (RV+ERV) (2.5
lts)
8. Total lung capacity – the
volume of air contained in the
lungs after the maximal
inspiration (TV+IRV+ERV+RV)
(6 lts)

35. Thank you…

36. Significance of FRC
4.Dilution of toxic inhaled
gases occurs due to the
reserve of 2300 ml of air in
the lungs (FRC) most of the
times.
5.Load on respiratory
mechanism and left ventricle
would be more if there was no
FRC.g