Pulmonary ventilation functions to maintain favorable concentrations of oxygen and carbon dioxide in the alveoli during rest and exercise. Inspiration occurs when intrapulmonary pressure is reduced below atmospheric pressure through contraction of inspiratory muscles, while expiration is usually a passive process at rest but involves expiratory muscles during exercise. Pulmonary ventilation, measured as minute ventilation, ensures complete gas exchange before blood leaves the lungs for transport throughout the body.

1. RESPIRATION II

2. Summary of pulmonary
ventilation
Pulmonary ventilation primarily functions to
maintain a fairly constant and favorable
concentration of oxygen and carbon dioxide
in the alveolar chambers during rest and
exercise.
Ensures complete gaseous exchange
before the blood leaves the lungs for
transport throughout the body.

3. Mechanics of Breathing
Pulmonary Ventilation = movement of
air from environment lungs
Process = bulk flow
The movement of molecules along a
passageway due to a pressure difference
between the two ends of the
passageway.

4. Inspiration
Inspiration = due to the pressure in the
lungs (intrapulmonary) being reduced below
atmospheric pressure.
Any muscle capable of increasing the
volume of the chest = inspiratory muscle

5. Cont’d
When the diagram contracts it forces
the abdominal contents downward and
forward and the ribs lift outward.
Results in a reduction of intrapleural
pressure expansion of the lungs
Effect of lung expansion on intrapleural
pressure and airflow

8. Expiration
Occurs when pressure within the lungs
exceeds atmospheric pressure
A passive process at rest
Mechanism
Expiration during exercise
Ms involved – rectus abdominus, internal
obliques
Contraction ↑ intrapulmonary pressure
and expiration

12. Airway Resistance
At any given rate of airflow into the lungs,
the pressure difference that must be
developed depends on the resistance of the
airways.
Basic flow equation applied:
Airflow = P1-P2
Resistance
P1-P2 = pressure difference at the two ends of
the airway
Resistance is the resistance to flow offered by
the airway

13. Cont’d
Airflow is increased at any time there
is an increase in the pressure gradient
across the pulmonary system.
Factors contributing to airway
resistance:
Diameter of airway
COPD, asthma

15. 3000
2000
COMPLIANCE = ∆V / ∆P
1000
Volume above FRC (ml)
=1000/5
∆V = 200 ml/cmH2O
FRC
∆P
0 -10 -20 -30
Intrapleural pressure (cmH2O)

16. Pulmonary Ventilation
V = volume
V (with dot) = volume per unit of time –
usually one minute
Subscribe T,D,A,I,E respectively:
Tidal
Dead space
Alveolar
Inspired
Expired

17. Cont’d
Refers to movement of gas into and
out of the lungs
Amount of gas ventilation per minute =
V = VT x f
Resting values for 70-kg male:
V = 7.5 L/min
VT = 0.5 L
f = 15

18. Cont’d
Maximal Exercise
V = 120-175 L/min
VT = 3-3.5 L
f = 40-50

19. Ventilation
Not all the air breathed reaches the
alveolar gas compartment.
Part of each breath remains in the
conducting pathways = VD = ventilation
dead space
The space that VD occupies =
anatomical dead space

20. Cont’d
The volume of inspired air reaching the
respiratory zone – alveolar ventilation = VA
Total Minute Ventilation:
V = VA + VD
Distribution of pulmonary ventilation
throughout the lung

21. Pulmonary Volumes and
Capacities
Spirometry
Measures inspired and expired gas
volumes

22. Definitions
Tidal Volume (VT) = vol of gas
inspired/expired during a normal
respiration cycle
Vital Capacity (VC) = max amt of gas
expired after a max inspiration
Residual Volume (RV) = vol of gas
in the lungs after a max expiration
Total Lung Capacity (TLC) = amt of
gas in lungs after max inspiration
VC + RV

24. Netter Physiology Figure 5.06
reproduced by permission from Netter’s Atlas of Human Physiology, by J.T.
Hansen and B.M. Koeppen, Teterboro NJ: Icon Learning Systems,2002

30. VA vs VE
TV Breathing Total VE Dead VA
(ml) Rate Space (ml/min)
(breaths/min) (ml/min) Minute
Ventilation
Shallow 150 40 6000 (150x40) 0
Breathing
Normal 500 12 6000 (150x12) 4200
Breathing
Deep 1000 6 6000 (150x6) 5100
Breathing

31. Dead Space vs Tidal Volume
Effect of tidal volume on dead space
Mechanism
Bottom line
Deeper breathing provides more effective
alveolar ventilation than a similar minute
ventilation achieved through an increased
breathing rate.

33. Blood Flow to the Lung
(Pulmonary Circulation)
Begins at pulmonary artery – receives
venous blood from Rt ventricle
pulmonary capillaries where gas
exchange takes place Oxygenated
blood flowing back into Lt atrium via
pulmonary vein.

35. Cont’d
C.O. of Rt vs Lt heart
Blood flow through Rt vs Lt heart
Pressure in Rt vs Lt heart
Mechanism
Effect of increased blood flow
Mechanism

39. Cont’d
Effect of position on blood flow within
lung
Standing
Exercise
Supine
Upside down

41. Ventilation
Concentration depends
on ventilation/blood
flow
Blood flow

42. Ventilation-Perfusion
Relationships
Normal gas exchange requires a
matching of ventilation to blood flow
(perfusion, Q)
The alveolus can be adequately
ventilated, but if blood flow to the
alveolus does not adequately match
ventilation, normal gas exchange does
not occur.

43. Cont’d
Ideal ventilation to perfusion ratio
(V/Q) = 1 or greater
i.e. a one to one matching of
ventilation to blood flow optimal gas
exchange
V/Q differences throughout the lung

44. Fig 10-13 text

46. Cont’d
A large V/Q represents a
disproportionately high ventilation
relative to blood flow poor gas
exchange
A V/Q lower then 1 represents a
greater blood flow vs ventilation in
the region of the lung being
considered
A V/Q > 0.5 = adequate to meet gas
exchange demands at rest

47. Physiologic Dead Space
Definition
Malfunctioning of alveoli:
1. underperfusion of blood
2. inadequate ventilation relative to
alveolar surface
Factors its increase

48. Netter Physiology Figure 5.19B
reproduced by permission from Netter’s Atlas of Human Physiology, by J.T.
Hansen and B.M. Koeppen, Teterboro NJ: Icon Learning Systems,2002

49. Perfect Lung

54. Gas Exchange and Transport

55. Factors dictating supply of O2 to body
1. Ambient air gas concentration
Concentration of atmospheric gases
O2
CO2
N2
2. Ambient air gas pressure
Barometric pressure
Value at sea level
Effect of weather and altitude

56. Diffusion of Gases
Partial Pressure
Dalton’s Law = the total pressure of a
gas mixture = the sum of the
pressures that each gas would exert
independently
Partial Pressure =
Percentage concentration x Total pressure of gas
mixture

57. Movement of Gas in Air and Fluids
Henry’s Law
Rate of gas diffusion:
1. pressure differential between the
gas above the fluid and the gas
dissolved in the fluid
2. solubility of the gas in the fluid

60. .
Vo2
FICK PRINCIPLE
-
C vo
2 Ca o
2
. .
-
Vo2 = Q ( Ca o - C vo )
2 2
.
. Vo2
Q =
-
Ca o - C vo
2 2

61. Blood and Circulation
O2 and CO2 in the Blood
Acid-base Balance

62. O2 and CO2 Transport in the Blood
Some O2 and CO2 are transported
as dissolved gases in the blood
Majority of O2 - Hb
Majority of CO2 – HCO-3

63. O2 in Solution
Effect of solubility on PO2 in solution
PAO2
Quantity dissolved
Typical blood volume = 5 L
Total volume of O2 dissolved
Ability to sustain life

64. Hemoglobin and O2 Transport
99% O2 transported in blood =
bound to Hb
O2 carrying capacity of Hb
Hb4 + 4 O2 Hb4O8
Oxyhemoglobin
Deoxyhemoglobin
Effect of PO2 in solution on Hb state

65. Cont’d
Amt of O2 that can be transported
per unit volume of blood is
dependent upon [Hb]
Normal [Hb]
Gender differences (m=150g; f=130g)
When completely saturated with O2,
each g of Hb can transport 1.34 ml
O2

66. Hemoglobin

67. PO2 and Hb Saturation
Cooperative binding = the binding
of one molecule to another
progressively facilitates the binding
of progressive molecules.

68. Oxyhemoglobin Dissociation Curve
Illustrates the saturation of Hb with
O2 at various PO2 values
% saturation = O2 combined with Hb x 100
O2 capacity of Hb
100 % saturation

69. Oxyhemoglobin Dissociation Curve
Combination of O2 + Hb in lungs =
loading
Release of O2 from Hb at tissues =
unloading
Reversible Reaction:
DeoxyHb + O2 OxyHb
Factors affecting reaction direction
1. PO2 in blood
2. Affinity of Hb for O2

70. Cont’d
Effect of high PO2
Effect of low PO2
Effect of ↓ affinity of Hb for O2
High PO2 in lungs high arterial PO2 ↑
oxyHb formation
Low PO2 in tissues ↓ PO2 in systemic
capillaries unloading of O2 to be used by the
tissues and increasing deoxyHb

73. O2 Transport Cascade

74. PO2 in the Lungs
Actual Hb-O2 saturation at sea level
Note sea-level alveolar PO2 of 100
mmHg
Effect of an ↑ alveolar PO2
Effect of PO2 < 60 mmHg on O2-Hb
saturation
Importance
Saturation at PO2 = 60 mmHg

76. PO2 in Tissues
Resting PO2 in cells
Dissolved O2 from the plasma diffuses
across the capillary membrane into cell
Effect on plasma PO2 and cellular PO2
Effect on Hb saturation
Hb saturation at cellular PO2
Resting (a-v)O2 difference

77. (a-v)O2 Difference
Definition
Resting values
Amount of O2 bound to Hb
Importance
Effect of exercise
PO2 = 2-3 mmHg – effect on O2-Hb

78. O2 Transport in Muscle
Myoglobin
Location
Composition
Affinity for O2

79. Myoglobin
Mb + O2 MbO2
Primary function

81. CO2 Transport in the Blood
CO2 transported in the blood in 3
forms:
1. dissolved CO2 (10%)
2. bound to Hb =
carbaminohemoglobin (20%)
3. HCO-3 = bicarbonate (70%)

83. CO2 Transport as Bicarbonate
CO2 in solution combines with H2O to
form carbonic acid
CO2+H2O H2CO3 (enzyme = carbonic anhydrase)
In tissues: CO2+H2O H2CO3 H++HCO-3
As tissue PCO2 ↑, CO2 binds with H2O to form
H2CO3 (carbonic acid). H2CO3 dissociates into
HCO-3 + H+. H+ combines with Hb and HCO-3
diffuses out of the RBC and into the plasma.

84. Control of blood acid-base balance
pH=6.1 + log (HCO-3 / CO2)