human physiology

1. Respiratory
Air Flow and
Volume

2. In this laboratory, you will be:
• Introduced to spirometry as a technique for recording respiratory
variables
• You will analyze a recording to derive respiratory parameters.
• You will examine lung volumes and capacities, as well as the
basic tests of pulmonary function and simulate an airway
obstruction.

3. Background
• Gas exchange between air and blood occurs in the
alveolar air sacs.
• The efficiency of gas exchange is dependent on
ventilation; cyclical breathing movements alternately
inflate and deflate the alveolar air sacs.
• Inspiration provides the alveoli with some fresh
atmospheric air and expiration removes some of the
stale air, which has reduced oxygen and increased
carbon dioxide concentrations.

5. Lung volumes and lung capacities
• Lung volumes and lung capacities refer to the volume of air
associated with different phases of the respiratory cycle.
• Lung volumes are directly measured;
• Lung capacities are inferred from lung volumes
• Instrument is spirometry

6. Lung volumes
Four types
1. Tidal volume
2. Inspiratory reserve volume
3. Expiratory reserve volume
4. Residual volume

7. Tidal volume
• Normal volume of air
inspired or expired
during quiet breathing
• TV = 500 ml

8. Inspiratory reserve volume
(IRV)
• It is maximal volume of air which can be
inspired after a normal inspiration.
• It is about 3000 ml

9. Expiratory reserve volume
(ERV).
• It is the maximal volume of air
which can be expired after a
normal expiration.
• It is about 1100 ml

10. Residual volume (RV)
• It is the volume of air remaining
in the lungs after maximal
expiration.
• It is about 1200 ml.

11. Lung Capacities
• These are combinations of two or more lung volumes.
1. Inspiratory capacity
2. Expiratory capacity
3. Functional residual capacity
4. Vital capacity
5. Total lung capacity

12. Inspiratory capacity (IC)
• Max volume of air that can be inspired after normal tidal
expiration IC = TV+IRV
= 500 +3000
= 3500 ml

13. Expiratory capacity
(EC).
• Max volume of air that can
be expired after normal
tidal inspiration
• EC=TV+ERV
(500+1100=1600ml) Expiratory
capacity
(EC).

14. Functional residual capacity
• Volume of air remaining in
lungs after normal tidal
expiration
• FRC= ERV + RV ( 1100 +
1200 = 2300ml)

15. Significance of FRC
› Continues exchange of gases
› So that concentration of O2 and CO2 is maintained
› Breath holding is made possible
› Dilution of toxic inhaled gases
› Prevents collapse of lungs

16. Vital capacity
• Max Amount of air
expelled after deepest
possible inspiration
• VC = TV+IRV+ERV
• 500+3000+1100= 4600ml
Vital
capacity

17. Total lung capacity
• Volume of air present in lung after max inspiration
• TLC = VC + RV ( 4600+1200 = 5800ml )

19. All lung volume and capacities are measured
directly by spirometer except :
• Functional Residual capacity FRC.
• Total lung capacity TLC.
• Residual volume RV.
• Because the air in the residual volume of the lung cannot be
expired into the spirometer and this volume constitutes part
of FRC, TLC.

20. Set up

22. Volume Correction

23. Exercise 1: lung volume and capacities

25. OBSTRUCTIVE VS. RESTRICTIVE
Obstructive disorders
• Characterized by: reduction in airflow.
• So, shortness of breath in exhaling air.
• ( the air will remain inside the lung
after full expiration )
• 1. COPD (Chronic obstructive
pulmonary disease).
• 2. Asthma
• 3. Bronchiectasis
Restrictive disorders
• Characterized by a reduction
in lung volume.
• So, Difficulty in taking air
inside the lung.
( DUE TO stiffness inside the lung
tissue or chest wall cavity )
1. Interstitial lung disease.
2. Scoliosis (sideways curvature of the
spine)
3. Marked obesity

30. OBSTRUCTIVE VS. RESTRICTIVE
Obstructive disorders
• Decrease in both FEV1 and
FEV1/FVC ratio .
Restrictive disorders
• Normal FEV1/FVC ratio .
Forced vital capacity (FVC):
The maximum volume of air forcibly exhaling from the point of maximal inhalation.
Forced expiratory volume in 1 second (FEV1):
Forced expiratory volume in 1 second during FVC maneuver.
Ratio of FEV1 and FVC (FEV1/FVC):
Expressed as percentage
Normal : 70% (and 65% in persons older than age 65).
Note : FEV1 Forced Expiratory Volume in the first second

33. Exercise 2
10 to 20 seconds.
Repeat twice more
***maximum Peak Inspiratory Flow
***Re-zero

34. Analysis

35. Exercise 3
The effects of bronchial obstructions such as asthma can be demonstrated
by making the following modification to the equipment.

36. Analysis

37. Exercise 4