Physiology of lung volumes and capacities

1. Physiology of lung volumes and
capacities

2. • Define lung volume and capacities.
• List factors affecting them and explain
the role of each factor

3. Pulmonary ventilation can be studied by
recording the volume movement of air into and
out of the lungs, a method called “spirometry”.
Introduction

4. Lung volumes: is the volume of air inespired or expired by
lungs associated with different phases of the respiratory cycle.
Lung capacities: consider to be two or more of the volumes
together.
There are statistic lung
volumescapacities and dynamic
lung volumes.

5. Dynamic
Static Tidal volume
Inspiratory reserve volume
expiratory reserve
residual volumes
forced vital capacity (FVC)
forced expiratory volume (FEV1)

6. Forced expiratory volume (FEV) measures how
much air a person can exhale during a forced breath
The amount of air exhaled may be measured during
the first (FEV1) of the forced breath.

7. The tidal volume is the volume of air inspired or
expired with each normal breath.
The inspiratory reserve volume is the extra volume
of air that can be inspired over and above the normal
tidal volume.

8. The expiratory reserve volume is the maximum extra
volume of air that can be expired by forceful expiration
after the end of a normal tidal expiration.
The residual volume is the volume of air remaining
in the lungs after the most forceful expiration

9. Lung capacities
Inspiratory capacity
Functional residual
capacity
Vital capacity
Total lung capacity

10. The inspiratory capacity equals the tidal volume plus
the inspiratory reserve volume.
The functional residual capacity equals the
expiratory reserve volume plus the residual volume.

11. The vital capacity equals the inspiratory reserve volume
plus the tidal volume plus the expiratory reserve
volume.
The total lung capacity is the maximum volume to
which the lungs can be expanded with the greatest
possible. It is equal to the vital capacity plus the residual
volume.

14. The lung volumes increase steadily from
birth to adulthood. The lungs mature at
the age of 20–25 years → only minimal
changes occur in the lung volumes in the
following 10 years .
After 35 years, aging is associated with
gradual changes in the lung volumes due
to:-
• Diminished alveolar elastic recoil.
• Depressed chest wall compliance.

15. Weight: depresses chest wall
compliance leading to marked decrease
in FRC and ERV.

16. /
Gender: males had larger lung size, more
respiratory bronchioles and wider airways
diameters compared with females

17. Ethnicity: white Americans of
European descent have larger trunk/leg
ratio, and consequently higher lung
volumes, compared with black
Americans of African descent.

18. Physical proprieties of lung include:
• Pulmonary compliance.
• Pulmonary resistance.

19. (RLD)associated with
diminished pulmonary
compliance which interfere
with lung expansion
1.All Lungs Volumes and
Capacities are reduced.
2. FVC% < 80%
3. FEV1% ≥ 80%
(OLD)obstructive ventilatory
associated with reduction of
maximal airflow from the lung
in relation to the maximal
volume (i.e. VC) that can be
displaced from the lung”.
1. Early VC is normal but lately
VC is ↓ and RV is ↑.
2. FVC% ≥ 80%
3. FEV1% < 80%
Pulmonary diseases like obstructive lung disease(OLD) and restrictive
lung disease (RLD).

20. Dynamic
Static Tidal volume
Inspiratory reserve volume
expiratory reserve
residual volumes
forced vital capacity (FVC)
forced expiratory volume (FEV1)

21. Forced expiratory volume (FEV) measures how
much air a person can exhale during a forced breath
The amount of air exhaled may be measured during
the first (FEV1) of the forced breath.

22. There are many factors affect lung
volumes/capacities include age, gender, weight,
height and ethnicity, physical activity, altitude
and others, which should be considered while
interpreting results of spirometry.

24. • Mayfield JD, Paez PN, Nicholson DP. Static and dynamic lung
volumes and ventilation-perfusion abnormality in adult
asthma. Thorax. 1971;26(5):591-596.
• Lutfi MF. The physiological basis and clinical significance of
lung volume measurements. Multidisciplinary Respiratory
Medicine. 2017;12:3. doi:10.1186/s40248-017-0084-5.
• Guyton and Hall 13th Edition
• WebMD