1. Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.
PowerPoint®
Lecture Slide Presentation by Robert J. Sullivan, Marist College
RESPIRATION
Chapter 37
PULMONARY VENTILATION
DR FARZANA MAJEED

2. Human Respiratory System
Figure 10.1

3. Respiratory system extracts oxygen from the
atmosphere , and the body utilizes the oxygen
and produce CO2 as a result of metabolism.
RESPIRATORY SYSTEM

4. Basic functions of the
respiratory system
1. Breathing (Pulmonary Ventilation) –
movement of air in and out of the lungs
• Inhalation (inspiration) draws gases into
the lungs.
• Exhalation (expiration) forces gases out
of the lungs.

5. Non –pulmonary functions:
2. Gas Conditioning – as gases pass
through the nasal cavity and paranasal
sinuses, inhaled air becomes turbulent. The
gases in the air are
• warmed to body temperature
• humidified
• cleaned of particulate matter
3. Protects respiratory surfaces
4. Site for olfactory sensation
5. Secretes pulmonary alveolar
macrophages
6. Endocrine functions

6. 7. Immune function
8. Vocalization
9. Coughing and sneezing to eliminate
irritants from respiratory tract
10. Production of surfactant

7. Respiration processes

8. Components of the Upper Respiratory
Tract
Figure 10.2

9.  Passageway for respiration
 Receptors for smell
 Filters incoming air to filter larger foreign
material
 Moistens and warms incoming air
 Resonating chambers for voice
Upper Respiratory Tract Functions

10. Components of the Lower Respiratory
Tract
Figure 10.3

11.  Functions:
 Larynx: maintains an open airway, routes food
and air appropriately, assists in sound production
 Trachea: transports air to and from lungs
 Bronchi: branch into lungs
 Lungs: transport air to alveoli for gas exchange
Lower Respiratory Tract

12. Mechanics of breathing
Pulmonary ventilation is accomplished
by two processes.
 Inspiration is an active process and
refers to inflow of air into the lungs. This
occurs when the intrapulmonary
pressure falls below the atmospheric
pressure.

13.  Expiration is a passive process and refers to
outflow of air from the lungs. This occurs
when intrapulmonary pressure exceeds the
atmospheric pressure.
 Changes in intrapulmonary pressure which
govern respiratory cycle are related to the
changes in intrapleural pressure.
 Changes in intrapleural pressure in turn
depend upon the changes in size of thoracic
cavity.

14.  Changes in size of thoracic cavity
depend upon the respiratory muscles
 Muscles of normal quiet inspiration are
diaphragm and external intercostal
muscles.
 Muscles of forceful inspiration are
sternocledomastoid, scalenes and
parasternals

15.  Normal quiet expiration is due to elastic
recoil of lungs
 Muscles of forceful expiration are
internal intercostals and abdominal recti

16. movements of inspiration
 It is an active process
 Normally produced by descent of
diaphragm and contraction of inspiratory
muscles
 Therefore diaphragm and external
intercostal muscles contract and cause
increase in vertical, antroposterior and
transverse diameters of thoracic cavity

18. Role of diaphragm
 Helps in 70-75% expansion of chest
during normal inspiration
 During inspiration , diaphragm contracts
and draw the central tendon part
downwards by 1.5cm in quiet breathing
and 7cm in deep respiration
 Cause an increase in vertical diameter
of the thorax

19.  Contraction of diaphragm also lifts the
lower ribs causing thoracic expansion
laterally and anteriorly
(the bucket handle and pump handle
movements respectively)

21. The respiratory muscles

22. Role of external intercostal
muscles
 Fibers of external intercostal muscles
are attached to vertebral ends of upper
and lower ribs
 Contraction leads to elevation of ribs
causing lateral and antro posterior
enlargement of thoracic cavity
 Bucket handle and pump handle
movements.

23. movements of expiration
 Passive phenomenon brought about by
elastic recoil of lungs
 Decrease in the size of thoracic cavity
by relaxation of diaphragm and external
intercostal muscles

24. mechanism of forced inspiration
 Forceful contraction of
diaphragm…..decent 7-10 cm as
compared to 1-1.5 cm in quiet breathing
 Forceful contraction of external
intercostal muscles……..increasing
transverse and AP diameter of thoracic
cavity

25.  Contraction of accessory muscles
 Sternocledomastoid contracts and lifts
the sternum upwards
 Anterior serrati and scaleni muscles
contract and lift ribs upwards

26. mechanism of forced expiration
 Contraction of abdominal muscles
causes increase in vertical diameter of
thoracic cavity
 Downward pull on the lower ribs by
contraction of internal intercostal
muscles decreases AP and transverse
diameter of thoracic cavity

29. Pressure and volume changes during
respiratory cycle
 Relationship between intrapulmonary pressure and
atmospheric pressure determines direction of air
flow
 In quiet breathing , at end expiration and at end
inspiration .no air is going in and out of the lungs
as the intrapulmonary pressure and atmospheric
pressures are equal i.e. 0 mmHg

30. Intra ALVEOLAR pressure
(IAP)
During normal quiet
inspiration
 IAP decreases to about -1
mmHg which is sufficient to
suck in 500 ml of air into
lungs within 2 sec.
 At the end of inspiration IPP
decreases again to 0 mmHg

32. During expiration
 IAP swings slightly towards positive
side (+1 mmHg) which forces 500 ml of
air out of lungs in 3 sec
 At the end of expiration IPP again
decreases to 0 mmHg

33. Significance
 Negative pressure in alveoli during
inspiration causes the air to enter into
alveoli but during expiration IAP
becomes positive so air is expelled out
of the lungs
 Helps in exchange of gasses between
air and lungs

34. Intrapleural pressure

35. During normal quiet inspiration
 It is negative pressure
 At the start of inspiration -5mmHg
which is the minimum amount of pressure to
hold the lungs open at resting level
 During inspiration becomes more negative
( -7.5mmHg)
During expiration
 All the events are reversed during expiration

36. significance
 As it is negative pressure so it prevents
the collapse of lungs after elastic recoil
 This also causes dilatation of larger
veins and vena cava. So act as suction
pump to pull venous blood from lower
part of the body to increase venous
return.

37. Transpulmonary pressure / recoil
pressure
 It is the difference between alveolar
pressure and pleural pressure.
SIGNIFICANCE
 It is the measure of elastic forces of
lungs that tend to collapse the lungs at
each instant of respiration

38. Pressure changes during inhalation
and exhalation

39.  Change in lung volume for each unit change in
transpulmonary pressure = stretchiness of lungs
 Transpulmonary pressure (TPP) is the
difference in pressure between alveolar
pressure and pleural pressure.
 Value of compliance of both lungs in normal
human adult =200ml of air/TPP in cm of H2O
LUNG COMPLIANCE
(Hysteresis)

40.  There are 2 different curves
according to different phases
of respiration.
 The curves are called :
Inspiratory compliance
curve
Expiratory compliance
curve
COMPLIANCE DIAGRAM

41.  Shows the capacity of lungs to “adapt” to
small changes of transpulmonary
pressure.
 compliance is seen at low volumes
(because of difficulty with initial lung
inflation) and at high volumes (because of
the limit of chest wall expansion)
 The total work of breathing of the cycle is
the area contained in the loop.

42.  Two forces try to collapse the
lungs
 Elastic forces of lungs
 Thin layer of fluid
 Two forces prevent collapse of the
lungs
 Intra pleural pressure
 surfactant

43. Major determinants of
compliance diagram
A.A. Elastic forces of the lung
tissue itself
B. Elastic forces of the fluid
that lines the inside walls of
alveoli and other lung air
passages (surface tension)

44. Elastic forces of the lungs
This is provided by
• Elastin and
• Collagen
interwoven in lung
parenchyma
Deflated lungs: fibers are contracted and in
kinked state
Inflated lungs: these fibers become stretched and
unkinked exerting more elastic forces

45. Elastic forces caused by surface
tension
Is provided by the
substance called
surfactant that is
present inside
walls of alveoli.

46. Experiment:
 By adding saline solution there
is no interface between air and
alveolar fluid. (B forces were
removed)
 surface tension is not present,
only elastic forces of tissue (A)
 Transpleural pressures
required to expand normal lung
= 3x pressure to expand saline
filled lung.

47. Conclusion of this experiment:
 Tissue elastic forces (A) =
represent 1/3 of total lung elasticity
 Fluid air surface tension elastic
forces in alveoli (B) = 2/3 of total
lung elasticity.

48. Surface tension
 water molecules are attracted to one
another.
 The force of surface tension acts in the plane
of the air-liquid boundary to shrink or minimize
the liquid-air interface
 In lungs = water tends to attract forcing air out
of alveoli to bronchi = alveoli tend to
collapse

49. Elastic contractile force of the entire
lungs (forces B)

50. Forces affecting lung compliance
 Deformities of thorax like
 Kyphosis
 Scoliosis
 Fibrosis
 Pleural effusion
 Paralysis of respiratory muscles

51.  Surface agent which tend to decrease
surface tension
Synthesized by type II alveolar cells
 Reduces surface tension (prevents
alveolar collapse during
expiration)
Consists of apoproteins +phospholipid
(dipalmitoylphosphatidylcholine) +
calcium ions
surfactant

52. Functions
 Decreases surface tension in alveoli
of the lungs
 Stabilize the alveoli which have
tendency to deflate
 Prevents bacterial invasion
 Cleans alveoli surface

53.  Plays important role in inflation of lungs
during birth. In fetal life it starts producing
after 3rd
month and completes at 7 months. Till
that time lungs remain collapsed. After birth
inflation of lungs takes place with initiation of
respiration due to CO2 induced activation of
respiratory centers. Although respiratory
movements are attempted again and again by
the new born tend to collapse the lungs.

54. Effects of deficiency of surfactant
 Infants: Collapse of the lungs called
Respiratory distress syndrome (RDS) or
hyaline membrane disease
 Adults: Collapse of the lungs called
Adult respiratory distress syndrome
(ARDS)

55.  Surface active agent in water = reduces
surface tension of water on the alveolar walls
Pure water (surface
pressure)
72
dynes/cm
Normal fluid lining
alveoli without
surfactant (surface
pressure)
50
dynes/cm
Normal fluid lining
alveoli with
surfactant
5-30
dynes/cm

56. Respiratory volumes and
capacities

57. Lung Volumes and Capacities
 Tidal Volume (VT)
 amount of air
entering/leaving
lungs in a single,
“normal” breath
 500 ml at rest,
↑ with ↑ activity
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

58.  Inspiratory Reserve
Volume (IRV)
 additional volume of
air that can be
maximally inspired
beyond VT by forced
inspiration
 3000 ml. at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

59.  Expiratory
Reserve Volume
(ERV)
 additional volume
of air that can be
maximally expired
beyond VT by
forced expiration
 1100 ml. at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

60.  Residual Volume
(RV)
 volume of air still in
lungs following
forced max.
expiration
 1200 ml. at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

61.  Total Lung Capacity
(TLC)
 total amount of air
that the lungs can
hold
 amt of air in lungs at
the end a maximal
inspiration
 VT + IRV + ERV +
RV
 5800ml at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

62.  Vital Capacity (VC)
 max. amt. air that
can move out of
lungs after a person
inhales as deeply as
possible
 VT + IRV + ERV
 4600ml at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

63.  Inspiratory Capacity
(IC)
 max amt. of air that can
be inhaled from a
normal end-expiration
 breathe out normally,
then inhale as much as
possible
 VT + IRV
 3500ml at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

64.  Functional Residual
Capacity (FRC)
 amt of air remaining in
the lungs following a
normal expiration
 ERV +RV
 2300ml at rest
IC
FRC
VC
TLC
Lung Capacities
Primary Lung
Volumes
IRV
VT
ERV
RV
Volume(ml)
0
6000

65. Forced Expiratory Volume
(FEVt)
 Amount of air forcibly
expired in t seconds
 FEVt = (Vt/VC) x 100%
 Normally…
 FEV1 = ~ 80% VC
 FEV2 = ~ 94% VC
 FEV3 = ~ 97% VC
 Index of air flow through
the respiratory air
passages
0 1 2 3
5000
4000
3000
2000
1000
0
Time (sec)Volume(ml)
FEV1 = (5000 ml -1000 ml) / 5000ml
= 4000 ml / 5000 ml
= 80%

66. Restrictive and Obstructive Disorders
 Restrictive
disorder:
 Vital capacity is
reduced.
 FVC is normal.
 Obstructive
disorder:
 VC is normal.
 FEV1 is < 80%.
Insert fig. 16.17
Figure 16.17

67. Air-Flow Disorders
 Obstructive disorders
 obstruction of the pulmonary air passages

air flow α radius4

slight obstruction will have large ↓ in air flow
 bronchiolar secretions, inflammation and edema
(e.g. bronchitis), or bronchiolar constriction (e.g.
asthma)
 reduced FEV, normal VC
 Restrictive disorders
 damage to the lung results in abnormal VC test

e.g. pulmonary fibrosis
 reduced VC, normal FEV

68. Ventilation
PULMONARY
VENTILATION
ALVEOLAR
VENTILATION
Cyclic process by which
fresh air enters and leaves
the lungs
Air utilized for gaseous
exchange
Product of TV and RR Product of TV excluding
dead space volume and RR
PV=TV X RR
500ml X 12/min
600ml or 6L/min
AV= (TV-DSV) X RR
(500-150) X 12/min
4.200ml or 4.2 L/min

69. Dead space
 Part of respiratory tract where gaseous
exchange doesn’t take place
 Types:
 Anatomical dead space
 Physiological dead space

70.  ANATOMICAL DEAD SPACE
Volume of respiratory tract from nose
up to terminal bronchiole
 PHYSIOLOGICAL DEAD SPACE
Includes anatomical dead space plus
well perfused but non ventilated alveoli
and well ventilated but non perfused
alveoli

71.  NORMAL VALUE OF DEAD
SPACE
Under normal conditions ADS + PDS
So DSV = 150 ml
 MEASUREMENT
BY N2 Wash method

72. Cough reflex
 Stimulus
irritants in the respiratory passages
 Receptors
in respiratory passageways
 Afferents
vagus nerve

73.  Centre
medulla
 Efferents
neuronal circuits
 Effectors / response
 2.5 ml of air rapidly inspired
 epiglottis gets closed

74.  vocal cords get approximated so air
trapped in
 abdominal muscles contract forcefully
so that pressure exceeds 100 mmHg or
more
 Epiglottis suddenly gets open, air
under high pressure in lungs exploded
out with the velocity of 70-100 miles
/hour