O2

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PB0
PB0
Inspiration
Expiration
Alveolar Air O2 100 mmHg
PAlt0
PAgt0
CO2 40 mmHg
O2
O2
venous
arterial
venous
arterial
CO2
CO2
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Chest Wall
Lung
Stuck Together
Ficks law J DA (?C/ ?X)
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Total Lung Capacity
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Inspiratory Reserve
Inspiratory Capacity
IR
IC
Vital Capacity
VC
Total Lung Capacity
TLC
VT
VT
Expiratory Reserve
ER
FRC
FRC
Residual Volume
RV
RV
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V1
V1
Equilibrate Concentration
C1V1N
C2(V1 VL) N
VL
VL
VL(C1/C2)V1 V1
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Inspiratory Reserve
Inspiratory Capacity
Vital Capacity
5 L
Total Lung Capacity
6.5 L
VT
600 ml
Expiratory Reserve
FRC
2.5 L
Residual Volume
1.2 L
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Chest Wall
Lung
Lung
Stuck Together
As we remove air from pleural space the lung
expands the chest wall gets pulled in.
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Balance of Forces Determines FRC Hookes Law F
-kx
Chest Wall Recoil Force
Increasing volume
Intrapleural space
Ppl -2
Normal FRC
Ppl -5
Ppl -8
Lung Wall Recoil Force
Decreasing volume
Ppl 0
Emphysema ? lung recoil
Fibrosis ? lung recoil
Pneumo- thorax
Normal
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LaPlace 2TPr P2T/r
P2
P1
For same T, P1gtP2 (I.e. 2T/r1 gt 2T/r2)
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?Surface Area ? ?Surface Tension
Lung Surfactant
Plasma
Surfactant 40 Dipalmitoyl Lecithin 25
Unsaturated Lecithins 8 Cholesterol 27
Apoproteins, other phospholipids,
glycerides, fatty acids
Surface Area (relative)
Water
Detergent
30
60
80
Surface Tension (dynes/cm)
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?Surface Area ? ?Surface Tension
Lung Surfactant

• Reduces Work of Breathing
• Increases Alveolar Stability (different sizes
  coexist)
• Keeps Alveoli Dry

Surface Area (relative)
Water
Detergent
30
60
80
Surface Tension (dynes/cm)
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Static Compliance Curves
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Balance of Forces Determines FRC Hookes Law F
-kx
Chest Wall Recoil Force
Increasing volume
Intrapleural space
Normal FRC
Ppl -5
Lung Wall Recoil Force
Decreasing volume
Normal
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Chest Wall
Apex
-8
-5
Lung has weight
Ppl -2
Base
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Regional- Apex to Base Differences
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Regional- Apex to Base Differences
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Apex to Base Differences
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Respiratory Cycle
Ppl
time
VT (L)
0.4
Respiratory Cycle Single VT Breath
-5
Rest FRC
0.2
0
Air Flow
-8
Inspiration
0
Inspiration
Expiration
-
Ppl (cm H2O)
-5
End Inspiration
-8
PB0
PA 0
Expiration

-6
-8
0.5
End Expi- ration-FRC
0
Air Flow (L/s)
-5
0
The linear Dashed trace is the Ppl required to
overcome recoil forces. More Ppl (solid curve) is
required to overcome airway resistance to
flow. N.B. ?P PA-PB ? ResistFlow.
-0.5
1
PA (cm H2O)
0
-1
1 2 3 4
time (sec)
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Respiratory Cycle
Ppl
time
VT (L)
0.4
Respiratory Cycle Single VT Breath
-5
Rest FRC
0.2
0
Air Flow
-8
Inspiration
0
Inspiration
Expiration
-
Ppl (cm H2O)
-5
End Inspiration
-8
PB0
PA 0
Expiration

-6
-8
0.5
End Expi- ration-FRC
0
Air Flow (L/s)
-5
Case of ZERO Resistance
0
-0.5
1
PA (cm H2O)
0
-1
1 2 3 4
time (sec)
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Respiratory Cycle
Ppl
time
VT (L)
0.4
Respiratory Cycle Single VT Breath
-5
Rest FRC
0.2
0
Air Flow
-8
Inspiration
0
Inspiration
Expiration
-
Ppl (cm H2O)
-5
End Inspiration
-8
PB0
PA 0
Expiration

-6
-8
0.5
End Expi- ration-FRC
0
Air Flow (L/s)
-5
0
The linear Dashed trace is the Ppl required to
overcome recoil forces. More Ppl (solid curve) is
required to overcome airway resistance to
flow. N.B. ?P PA-PB ? ResistFlow.
-0.5
1
PA (cm H2O)
0
-1
1 2 3 4
time (sec)
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Respiratory Cycle
Ppl
time
VT (L)
0.4
Respiratory Cycle Single VT Breath
-5
Rest FRC
0.2
0
Air Flow
-8
Inspiration
0
Inspiration
Expiration
-
Ppl (cm H2O)
-5
End Inspiration
-8
PB0
PA 0
Expiration

-6
-8
0.5
End Expi- ration-FRC
0
Air Flow (L/s)
-5
Case of HIGH Resistance
0
-0.5
1
PA (cm H2O)
0
-1
1 2 3 4
time (sec)
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Dynamic Compression of Airways
Mild Expiratory Effort (P13)
Normal at FRC
-5
0
0
PTP5 PPl - PA -5
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Dynamic Compression of Airways
Low VL Basal Alv also like this
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Normal
Inspiration
Volume
? Recoil Restrictive
?Resistance Obstructive
FRC
time (sec)
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Forced Vital Capacity
Normal
TLC
FEV1.0
FVC
RV
1 sec
FEV1.0 4 L FVC 5 L 80
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Flow-Volume Curves
Effort Independent limb in forced expiration.
Expiratory Flow
Due to Dynamic Airway Compression and airway
collapse.
TLC
RV
Lung Volume
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9
Normal
Obstructive
Flow Rate (L/sec)
Restrictive
9 8 7 6
5 4 3 2
1
Lung Volume (L)
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Critical Closing Volume Test
TLC
RV
4.
40
1.
3. Alveolar Plateau
2. Dead Space Washout
N2 Concentration ()
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Closing Volume
6 5 4 3
2 1
Lung Volume (L)
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Apex to Base Differences
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Critical Closing Volume Test
TLC
RV
4.
40
1.
3. Alveolar Plateau
2. Dead Space Washout
N2 Concentration ()
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Closing Volume
6 5 4 3
2 1
Lung Volume (L)
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PO2100 mm Hg 21 ml O2/dL
PO2100 mm Hg 21 ml O2/dL
O2
O2
PO2100 mm Hg 0.3 ml O2/dL
PO2100 mm Hg 0.3 ml O2/dL dissolved20 ml O2/dL
HB-O2
O2
O2
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The Bohr Equation VD1 (PACO2 PECO2)???
???????? VT PACO2 VD2 (PaCO2
PECO2)??? ???????? VT PaCO2
D. Sample Calculation VT 600 ml
PACO2 38 mmHg PECO2 28 mmHg PaCO2
40 mmHg VD1 600(38 28)/38 158 ml VD2
600(40 28)/40 180 ml E.Alveolar
Ventilation . . . VE VD VA
VT ? frequency . . . VA VE -
VD .1.For VT 500 ml, f 10/min, VD
150 ml, what is VA? .VA 5000 - 1500
3500 ml/min . .2.If VE is doubled by
increasing VT what is VA? 10,000 - 1500 8500
ml/min . .3.If the same VE is
obtained by doubling frequency, what is VA?
10,000 - 3000 7000 ml/min .Thus
increasing VT rather than frequency is more
effective for ? VE.
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F. Alveolar Ventilation and CO2 production
. VCO2 Expired CO2 - Inspired CO2
. VA ? FACO2 . VA x PACO2
??????? PA . .VCO2 ? K
VA ??????????? PACO2
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XIV. RESPIRATORY GAS CASCADE PO2 PCO2 mm
Hg mm Hg??????????????????????????????????? Air
(dry) 760 ? 0.21 160 0 Trachea (humidified
760-47) 713 ? 0.21 150 0 Alveolus (some O2
absorbed by blood) 100 40 Arterial (R-L
Shunt) 90 40 Mixed venous (O2 absorbed by
tissues) 40 46
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O2 Diffusion in Pulmonary Capillaries (transit
time)
100
Thickened Alveolar Membrane
80
60
PO2 mm Hg
Normal Transit Time
40
Exercise Shortens Transit time
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0.75
0.25
0.5
time in Capillary (sec)
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Tissue CO2 Loading O2 Unloading
CO2
O2
Capillary Wall
Cl-
O2
CO2
c.a.
CO2 H2O ? H2CO3 ? H HCO3-
H HbO2 ? HHb O2
Carbamino HHb-CO2
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Lungs CO2 Unloading O2 Loading
CO2
O2
Alveolar Wall
O2
HCO3-
CO2
Cl-
c.a.
CO2 H2O ? H2CO3 ? H HCO3-
H HbO2 ? HHb O2
Carbamino HHb-CO2
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Ventilation Perfusion Ratios
PO2 150 PCO2 0
PO2 40 PCO2 45
PO2 150 PCO2 0
PO2 100 PCO2 40
No flow
CO2 45
.
.
.
Normal VA/Q
Low VA/Q
High VA/Q
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50
PCO2 (mm Hg)
50
100
150
PO2 (mm Hg)
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3
Perfusion
.
VA/Q
2
Flow of Blood or Air
.
VA/Q Ratio
Ventilation
1
Distance up Lung
Top
Bottom
.
.
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Mechanisms of Hypoxemia PaO2 PaCO2 PO2
(A-a) PaO2 with 100 O2 ?????????????????????????
??????????????Hypoventilation low High Norm gt550
Diffusion low norm-low high gt550R-L
Shunt low norm-low high lt550 . VA/Q
Imbalance low norm-lo-hi high gt550

• Other Hypoxemias (without low PaO2)
• Anemia
• Carbon Monoxide
• Hypoperfusion (CV problem)

• Local Control
• Low PAO2 ? vasoconstriction
• Low PVCO2 ? bronchoconstriction

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Peripheral Chemoreceptor Responsiveness
75
50
maximal firing rate
25
50
100
500
Arterial PO2 (mm Hg)
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BBB
CSF
Plasma
CO2 ?? HCO3 H
CO2 HCO3 H
Pumped
CNS Acidosis then HCO3 is pumped in ( restores
pHCNS faster than kidneys can restore pHsystemic)
Respiratory Acidosis (?PaCO2)
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BBB
CSF
Plasma
CO2 ?? HCO3 H
CO2 HCO3 H
CNS Alkalosis !!!! (then pump HCO3 out)
Metabolic Acidosis
Hyperventilation ?PaCO2
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Ventilatory Response to O2
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Ventilatory Response to CO2
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Ventilatory Response to CO2
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BBB
CSF
Plasma
CO2 ?? HCO3 H
CO2 HCO3 H
When pHCNS returns to norm (HCO3 pumped out) VE
is less restrained
Respiratory Alkalosis
high pHCSF limits Hyperventilation