Transcript 16 - Pegasus @ UCF

Chapter 16
Dr. D. Washington
Respiratory Physiology
The term respiration includes three
separate but related function:
A. Ventilation (breathing): mechanical
movement of air between nose and
alveoli of the lungs
B. Gas exchange: between the air
and the blood; and between the
blood and tissues
C. Oxygen utilization: cellular
metabolism
E.R. Weibel’s Model of the Human Airways
(Morphometry of the Human Lung)
Conductive Zone
T
Br
BL
Trachea
0
1
2
3
4
Bronchus
Bronchioles
Transinonal or
Respiratory Zone
TBL
Terminal bronchioles
RBL
17
18 Terminal bronchioles
AD
21 Alveolar ducts
AS
23
Alveolar sacs
Functional Unit of the Lungs
Surfactant decreases
the surface tension
of fluids linings the
Alvelus
alveoli.
Law of LaPlace: the
distending pressure
v
(P) in a distensible,
hollow object is equal
at equilibrium to the
tension (T) in wall
T
divided by the 2
principal radii of
curvature of the
P
objects (R1 and R2).
Secretory cells (type II)
(Surfactant)
Squamous cells
(type I)
Interstitium basement
membranes of
capillary & alveolus
Surface tension caused
by the cohesive forces
of water molecules
Air pressure inside
the alveolus
Surfactant Effects
Without Surfactant
The clamps represent
the forces of surface
tension. The greater
pressure on the
small alveolus would
cause it to collapse.
With Surfactant
The pressure on the
small alveolus is
reduced.
Lung Vol. Change (liters)
Pressure - Volume Curve
(Compliance)
.50 _
.25_
-4
+3
-5
0
-6
-3
-7
-4
 Intrapleural pressure (cm H20)
(pressure around the lungs)
Intrapulmonary pressure
Negative pressure = subatmospheric pressure
Changes in Compliance
A. Decrease (increased resistance)
1. Aleolar edema: decrease caused by
increase in pulmonary venous pressure
2. Atelectasis: partial or complete collapse of
lungs
3. Pulmonary fibrosis: infiltration or
connective tissue
B. Increase (decrease resistance)
1. Age: loss of elastic tissue
2. Emphysema: destruction of alveolar tissue
Elastic Properties of the Lungs
(vol. measured
on spirometer)
pump
Excised dog lung
When the pressure inside the jar is
reduced below atm. Pressure,
the lung expands.
Lung Volumes
150 ml
1,000 ml
1,000 ml
500 ml
3,000 ml
Dead space
Residual volume
Expiration Reserve volume
Tidal volume
Inspiration Reserve volume
Lung Capacities
(combination of volumes)
IRV
IC
TV
FRC ERV
RV
RV
TLC VC
TLC - total lung capacity
VC - vital capacity
IC - inspiration capacity
FRC - function residual capacity
Lung Compartments
Inspiration Reserve volume
Tidal volume
Expiration Reserve volume
Residual volume
Note: If the anatomical dead space is 150ml,
and the tidal volume is 500 ml;
the percentage of fresh air reaching the
alveoli is 350/500 X 100% = 70%
Composition of Gases at Sea Level
Oxygen
PP
%
Inspirated air
(20oC; 50%Sat.)
Moist tracheal
air (saturated)
Alveolar air
Arterial blood
Venous blood
Expired air
CO2
PP
%
Water
PP
%
Nitrogen &
rare gases
PP
%
158 21.
0.3
0.04
8
1.
594
78
149
19.6
0.3
0.04
47
6.2
564
74
104
100
40
116
13.7
13.
5.6
15.2
40
40
46
29
5.3
5.3
6.5
4
47
47
47
47
6.6
6.2
6.7
6.2
569
573
573
568
75
75
81
75
PP = Partial Pressure
Partial Pressure in the Body
Inspired Air
O2 = 158
CO2 = 0.3
H20 = 8
N2 = 594
Right Heart
O2 = 40
CO2 = 46
H20 = 47
N2 = 573
Dead
space
Veins
Alveoli
O2 = 104
CO2 = 40
H20 = 47
N2 = 569
Expired Air
O2 = 116
CO2 = 29
H20 = 47
N2 = 568
Left Heart
O2 = 100
CO2 = 40
H20 = 47
Arteries N2 = 573
Capillaries
O2 = 40, CO2 = 46, H20 = 47, N2
= 573
Coordination of Ventilation &
Perfusion



The efficiency of gas exchange in the
lungs is dependent on the adequacy
and uniformness of ventilation and
perfusion.
Inspired gas and pulmonary blood
flow are unevenly distributed.
Ventilation-perfusion ratio inequality
is the most common clinical cause of
arterial hypoxemia.
Coordination of Ventilation &
Perfusion



Ventilation-Perfusion Ratio
VA/Q = 0.8 in a normal person at rest
Volume of blood perfusing the lungs
is 1.2 times greater than the Volume
of air ventilating the lungs
Coordination of Ventilation &
Perfusion

Pathological causes for
Non- Uniform Distribution of
Ventilation
1. Regional Elasticity of Changes
(pulmonary fibrosis)
2. Regional Obstruction of Airways
3. Intrathoracic fluid Accumulation
Coordination of Ventilation &
Perfusion

Pathological causes for
Non- Uniform Distribution of
Perfusion
1. Compression of Blood Vessels Caused
by Intrathoracic P.
2. Embolism
3. Regional Vasoconstriction (ANS)
Regulation of Respiration
I. Intrinsic
Medulla of Respiratory Center found
in the brain stem
Regulation of Respiration
II. Extrinsic
A. Chemoreceptors
1. Peripheral
carotid and aortic bodies
2. Central Nervous System (Medulla)
70 - 80% main cause for change
Regulation of Respiration
II. Extrinsic
B. The Hering-Breuer reflexes
Maintains normal tidal volume.
(more important in infants)
1. H-B inflation reflex
2. H-B compression reflex
Respiratory Center
Cortical & midbrain stimuli
Pneumotaxic
inhibits respiration
Apneustic
stimulates respiration
Medullary
rythmicity center
Impulses to
respiratory
muscles
glassopharyngeal
& vagus
Cord facillatory
impulses
Rhytmic Oscillation in the
Respiratory Center
inspiratory
expiratory
I
neurons
E
neurons
muscles of
inspiratory
muscles of
expiratory
Respiration neurons in Brain Stem
Dorsal View; Cerebelium removed
A
Parabrachials N.
(pneumotaric center)
B
Middle cerebellar
peduncle
C
Apneustic center
in 4th ventrical
Dorsal group
respiratory neurons
Ventral group
respiratory neurons
IX
X
All transected
in A & B
XI
XII
D
Vagi intact
Vagi cut
Respiration neurons in Brain Stem
Dorsal View; Cerebelium removed
Effects of Transection
A. Above pons - regular breathing continues
B. Below pneumotaxic area - inspiratory neutrons

fire continuously ( sustained inspriation apneusis. However, if the vagus is intact
respiration continues (effects from lungs).
C. Below apneustic area - gasping type irregular
respiration continues with or with our vagus
D. Below medulla - respiration stops
(phrenic nerve cut)
Decreased ventilation
Increased arterial Pco2
Plasma CO2
Blood
CSF
Chemoreceptors
in medulla oblongata
Respiratory center
in medualla oblongata
Spinal cord
motor neurons
Blood pH
Chemoreceptors
in aortic &
carotid bodies
Sensory neurons
Respiratory
muscles
Increased ventilation
Negative
feedback
Effects of Po2, Pco2 + ph on Alveolar Ventilation
Alveolar Ventilation
(basal rates)
Fluctuation of one variable at a time
Co2
ph
7
6
5
4
3
2
1
0
Pco2 35
40
Po2 120 100
ph
7.5 7.4
O2
45
80
7.3
50
60
7.2
55
40
7.1
Effects of Po2, Pco2 + ph on Alveolar Ventilation
Free Fluctuation
Co2
ph
O2
Pco2
Po2
ph
40
100
7.4
Oxygen Solubility
Henry’s Law
The concentration of a gas dissolved in a
fluid is directly proportional to the
partial pressure of that gas.
Solubility Coefficients of O2 in blood =
24cc/L/atmos.
Arterial Po2 = 100mmHg
therefore,
100mmHg x 24cc/L
dissolved O2 =
= 3/15cc/l
760 mmHg
Heme
CH3
CH
C
C
HC C
CH3
C
N
CH2
C
CH2
COOH
C CH
N
C
C
HC C
CH2
C C CH3
Fe N
C C
N
C CH
C
C
CH2
CH3
CH2
COOH
C
CH2
20
100
80
15
60
10
Veins
(at rest)
40
5
20
Arteries
0
0
0
20
40
Po2
60
80
(mm Hg)
100
Amount of O2
unloaded
to Tissues
Ozygen content
(ml O2/100 ml blood)
Percent oxyhemoglobin saturation
Effect of Changes inPo2 on Blood
Oxyhemoglobin Saturation and
Oxygen Content (figure 15.34)
7%
hemoglobin
100
myglobin
80
% Saturation
38% dissociated
Oxygen Dissociation
60
50
40
20
0
0
20
40 60
80 100
O2 pressure mmHG
half saturations
myglobin = 6mm Hg
hemoglobin = 24 mm Hg
Oxygen Dissociation
Th O2 dissociation curve for myoglobin
follows the law of mass action
Mb +Po2
K=
Mbo2
with a dissociation constant of 3.3, the
Po2 has to fall almost to 0 before the O2
is releases to the cells
% O2 saturation
Bohr Effect
(effect of pH on O2 Dissociation)
pCO2 = 20 high pH,
shift left
pCO2 = 80 low pH,
shift right
100
80
60
pCO2 = 40
pCO2 = 80
pCO2 = 20
40
20
0
0 20
40 60 80 100
Po2
A drop in pH at any pO2, causes an In O2
Dissociation.
Bohr Effect
(effect of pH on O2 Dissociation)
Factors affecting O2 Dissociation
1. pH (or Co2 ) - deoxyhemogloblim
binds H+ more actively then
oxyhemogloblim
2. Temperature - effects metabolic rate
[CO2]
CO2+ H20 H2O H2CO3 H+ + HCO3
3. 2,3 - DPG (diphosphoglycerate)
of RBC.
Carbon Dioxide Transport the Chloride
Shift in Tissue Capillaries
Tissue Cells
CO2 dissolved in plasma (10%)
CO2 combined with
hemogloblin to form
carbaminohemoglobin
(20%)
CO2
Carbonic anhydrase
CO2+ H2O
H2CO3
Red blood cells
Plasma
-
H2CO3
H++HCO3 -
H+ combines
with hemoglobin
Cl Chloride shift
HCO 3 (70%)