2. 11-Apr-24 Lung Volumes 2
Lung Volumes
Tidal volume 500 ml
Anatomical dead
space 150 ml
Alveolar gas
3000 ml
Pulmonary capillary
blood 70 ml
Total ventilation
7500 ml/min
Frequency = 15
per min
Alveolar
ventilation
5250 ml/min
Pulmonary
blood flow
5000 ml/min
3. 11-Apr-24 Lung Volumes 3
Determination of Lung
Volumes
Mouth
piece
Water filled spirometer
Recoding
drum
4. 11-Apr-24 Lung Volumes 4
Lung Volumes
Volume of air in the
lungs can be
subdivided into 8
components
Most important
• Tidal volume
• Vital capacity
• Functional residual
capacity
• Residual volume
• Total lung capacity
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
5. 11-Apr-24 Lung Volumes 5
Tidal Volume
Volume of air
• Inspired or expired
during breathing
It is about 500 ml
One of the
determinants of
minute ventilation
• Pulmonary
ventilation
• MV = TV * RR
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
6. 11-Apr-24 Lung Volumes 6
Inspiratory Reserve
Volume IRV
Volume of air
• That can be taken in
by maximal
inspiratory effort
• Over and above TV
• It is about 3000 ml
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
7. 11-Apr-24 Lung Volumes 7
Expiratory Reserve Volume
ERV
Volume of air
• That can be expelled
by most powerful
expiratory effort
• After tidal air has
been expelled
• It is about 1100 ml
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
8. 11-Apr-24 Lung Volumes 8
Residual Volume
Volume of gas in lungs
at end of maximal
Voluntary effort (1200
ml)
Will increase if
• force required to
decrease lung vol.
Becomes greater
• Decrease in elasticity -
emphysema
• Stiffer chest wall -
pleural thickening,
oesteoarthritis
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
9. 11-Apr-24 Lung Volumes 9
Residual Volume
• Voluntary muscular
force decreases
• Pain,
neuromuscular
weakness
Will increase
• Presence of airway
obstruction
• Air trapping
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
10. 11-Apr-24 Lung Volumes 10
Vital Capacity
Vol of air expelled by
maximal voluntary
expiration following
maximal inspiration
(IRV + Vt + ERV) =
4600 ml
Great variation
Depends on height &
age
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
11. 11-Apr-24 Lung Volumes 11
Vital Capacity
Reduction in vital
capacity
• Decrease lung gas
volume
• Space occupying lesion
• Decreased ability to
expire or inspire
maximally
• decrease muscular
force, pain,
neurological diseases
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
12. 11-Apr-24 Lung Volumes 12
Vital Capacity
• Increase resistance
to chest cage
expansion
• Increase resistance
to expansion of lung
• Pleural thickening,
asthma
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
13. 11-Apr-24 Lung Volumes 13
Inspiratory Capacity
Volume of air that
can be inspired
from the end of
expiration
• IRV + Vt
• It is about 3500
6
1.1
0
1.7
1.2
IRV
Vt
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
14. 11-Apr-24 Lung Volumes 14
Functional Residual
Capacity
Volume of gas in the
lungs
• At the end of normal
expiration
• (ERV + RV)
Position at which
tendency of
• Lung to collapse is
equal to
• Elastic and muscular
force of chest cavity
causing it to expand
Affected by
• Body position, anxiety,
pregnancy
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
15. 11-Apr-24 Lung Volumes 15
Functional Residual
Capacity
FRC is the lung volume
• Gas exchange takes
place
With each tidal breath
• Fresh gas mixes with
alveolar gas
Small fluctuation of
• Alveolar & arterial gas
tensions
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
16. 11-Apr-24 Lung Volumes 16
Functional Residual
Capacity
FRC acts as a buffer
Maintain relative
constant
• Alveolar & arterial gas
tension
Prevent rapid change
in alveolar gas
• When there is change
in ventilation or
inspired gas
↑ Lung volume during
quiet breathing
• ↓Work of breathing
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
17. 11-Apr-24 Lung Volumes 17
Total Lung Capacity
Vital capacity +
Residual volume
• 5800 ml
All pulmonary
volumes are 20 to
25% less in females
6
1.1
0
1.7
1.2
IRV
TV
ERV
RV
VC
FRC
IC TLC
Inspiration
Expiration
18. 11-Apr-24 Lung Volumes 18
Forced Expiratory Volume
FEVt or
Timed vital
capacity
Subject inspires to
TLC
• Then exhales as
rapidly as possible to
RV
6
1.1
0
1.7
1.2
TV
Inspiration
1 2 3
0
Time in seconds
19. 11-Apr-24 Lung Volumes 19
Forced Expiratory Volume
The spirometer record
both
• Volume expired over
• Preset time interval
It is a measurement of
the
• Rate at which a
maximal inspiration
can be completely
exhaled
6
1.1
0
1.7
1.2
TV
Inspiration
1 2 3
0
Time in seconds
20. 11-Apr-24 Lung Volumes 20
Forced Expiratory Volume
Normal person can
exhale
• 68% of VC at 0.5 sec
• 77% of VC at 0.75 sec
• 84% of VC at 1 sec
• 94% of VC at 2 sec
• 97% of VC at 3 sec
Ratio known as
FEV1/FVC %
6
1.1
0
1.7
1.2
TV
Inspiration
1 2 3
0
Time in seconds
FEV1
FVC
