1. PULMONARY VENTILATION
DR AMNA TAHIR
ASSISTANT PROFESSOR
PHYSIOLOGY DEPARTMENT

2. PULMONARY VENTILATION
It means the inflow and outflow of air between the atmosphere and the lung alveoli
Movement of air in and out is brought by changes in size and volume of thoracic cavity which lungs passively following these changes ( so lungs have no active role to play in breathing mechanism)

3. PRESSURES IN PLEURAL CAVITY
PLEURAL PRESSURE
It is a negative pressure in pleural cavity which keeps the lungs expanded . During inspiration this pressure becomes more negative so lungs become more expanded .Normally it is -5 cm of water and become -7.5 cm of water during inspiration. During expiration the event essentially reversed

4. PRESSURES IN PLEURAL CAVITY
Alveolar pressure
It is the pressure of air inside the lung alveoli .
When the glottis is open and no air is flowing into or out of lung ,the pressure in all parts of respiratory tree ,all the way to alveoli ,are equal to atmospheric pressure , which is considered to be zero reference in the airways… 0 cm of water

5. During inspiration the pressure in the alveoli falls below atmospheric pressure ( below zero ) to cause inward flow of air into the alveoli .
So during inspiration it becomes - 1 cm of water and becomes + 1 cm of water in expiration .

6. TRANSPULMONARY PRESSURE
DIFFERENCE BETWEEN Alveolar pressure AND PLEURAL PRESSURE
DURING THERE PRESSURE CHANGE IN INSPIRATION THERE IS INCREASE IN LUNG VOLUME OF 0.5 LITER AND IN EXPIRATION THIS 0.5 LITER MOVES OUT S

7. Volume and Pressure Changes
Figure 16.13
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8. PULMONARY VENTILATION: MECHANISM
During inspiration inspiratory muscles contract so size of thorasic cavity increases in all direction
Pleural pressure becomes more negative( sub atmospheric) alveolar pressure also becomes below atmospheric pressure
Air moves into the lungs .

9. PULMONARY VENTILATION: MECHANISM
During quite expiration ,when inspiratory muscle relax , size of thoracic cavity decreases
Pleural pressure becomes less negative , lungs are less expanded ,alveolar pressure rises above atmospheric preesure
air moves out of lungs
BASIC FACTOR IS THE CHANGE IN SIZE AND VOLUME OF THORACIC CAVITY

10. PULMONARY VENTILATION: MECHANISM
4/28/2017
Pressure gradients are established by changes in the size of the thoracic cavity that are produced by contraction and relaxation of muscles (Figures 24-4 and 24-5)
Boyle’s law: the volume of gas varies inversely with pressure at a constant temperature
Inspiration: contraction of the diaphragm and external intercostals produces inspiration; as they contract, the thoracic cavity becomes larger (Figures 24-6 and 24-7)
Expansion of the thorax results in decreased intrapleural pressure, leading to decreased alveolar pressure
Air moves into the lungs when alveolar pressure drops below atmospheric pressure
Compliance: ability of pulmonary tissues to stretch, thus making inspiration possible

13. Chest Wall and Pleural Sac
Figure 16.7
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14. Pulmonary Pressures Figure 16.8a–b
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22. 4/28/2017

23. Minute Ventilation
Total volume of air entering and leaving respiratory system each minute
Minute ventilation = VT x RR
Normal respiration rate = 12 breaths/min
Normal VT = 500 mL
Normal minute ventilation =
500 mL x 12 breaths/min = 6000 mL/min
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24. Dead Space and Ventilation
Fresh air
“Old air”
Alveolus
Conducting
zone
(anatomical
dead space)
Expiration
Inspiration
Exchange with blood
CO2 O2
(a)
(b)
(c)
Figure 16.17
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25. Respiratory Rate and Ventilation
Table 16.1
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26. Alveolar Ventilation
Volume of air reaching the gas exchange areas per minute
Alveolar ventilation =
RR X (VT- VD)
Normal = 4200 mL/min
12 X( )
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27. DEAD SPACE
It is the portion of inspired air that does not take part in gaseous exchange with pulmonary capillary blood
Tidal volume ; It is the volume of air inspired or expired with each normal breath .It is about is 500 ml in the adult male.
Out of 500ml ,350 ml goes to alveoli
150ml remains in conducting airways.

28. Definitions of Dead Space
Anatomic Dead Space
Physiologic Dead Space
Low Blood Flow
Copyright © 2006 by Elsevier, Inc.

29. Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

31. Copyright © 2007 Lippincott Williams & Wilkins.
McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition

33. Respiratory Zone Figure 16.3 (3 of 3)
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34. Anatomy of the Respiratory Zone
Figure 16.5a
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35. TYPES OF DEAD SPACE
ANATOMICAL DEAD SPCAE
PHYSIOLOGICAL DEAD SPACE

36. Alveolar dead space ANATOMICAL DEAD SPCAE
Consist of conducting airways= 150 ml
Physiological dead space = anatomical dead space + alveolar dead space
Alveolar dead space
Consists of nonfunctional or partially functional alveoli or lack of perfusion
Wastage ventilation

37. Physiological dead space = anatomical dead space as normally alveolar dead space is absent
Dead space starts from nose to terminal bronchiole
When we expire out first 150 ml comes from dead space expired out,then 350 ml from ventilation area is expired out s

38. Disadvantages of dead space

39. Measurement of ANATOMICAL DEAD SPCAE
by Nitrogen Washout method
Measurement of Physiological dead space by Bohr’s method s

40. Measurement of ANATOMICAL DEAD SPCAE by Nitrogen Washout method

41. Measurement of Physiological dead space by Bohr’s method

42. Factors that increase dead space
Factors that decrease dead space